HYDRAULIC INVESTIGATION OF STREAM RESTORATION … · 2017-11-17 · 1 CHAPTER 1: INTRODUCTION Introduction The damming of U.S. streams and rivers has occurred since colonial times

HYDRAULIC INVESTIGATION OF STREAM RESTORATION

METHODS IN A THIRD ORDER, DAM REMOVAL-IMPACTED

MOUNTAIN STREAM LOCATED IN THE VALLEY-RIDGE

PROVINCE, ADAMS COUNTY, PENNSYLVANIA

By

Zachary R. Phillips

A Thesis

Submitted to the Department of

Geography and Earth Science and the Graduate Council

in partial fulfillment of the requirements for the degree of

Master of Science

SHIPPENSBURG UNIVERSITY

Shippensburg, Pennsylvania

January, 2016

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Acknowledgements

First, I would like to thank Shippensburg University of Pennsylvania, and

their Geography and Earth Science Department for supporting this research. Most

importantly, I thank Dr. Scott Drzyzga for initiating my interest in the science

behind dam removals, Dr. Sean Cornell for acquiring the necessary surveying

equipment, and Dr. Christopher Woltemade for introducing me to the HEC-RAS

modeling system. To you all, thank you for advising my work and taking the time

from your busy schedules to help me. Specifically, I thank my father George Phillips

for teaching me to have a good work ethic and my mother Barbara for making sure

it was well-directed. I thank my sister Sydney for her friendship and support

throughout my life. Of course, not to be forgotten are the people whom helped

complete the three week long bathymetry surveying project. These people are;

Emery Saylor, Caz Guzowski, Molly Moore, and Jim Mason. Thank you for being

such great friends. This project never would have been possible without your help

and willingness to spend your time standing in a stream (even in the middle of

January). To all of you, thank you for making this research possible.

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Table of Contents

Acknowledgements ...................................................................................................................... i

Table of Contents ......................................................................................................................... ii

List of Figures .............................................................................................................................. vi

List of Tables .............................................................................................................................. viii

ABSTRACT .................................................................................................................................. ix

CHAPTER 1: INTRODUCTION ................................................................................................ 1

Introduction .............................................................................................................................. 1

Statement of Purpose ............................................................................................................... 2

Research Questions .................................................................................................................. 4

CHAPTER 2: STUDY AREA....................................................................................................... 5

Introduction .............................................................................................................................. 5

Characteristics of the Contributing Watershed ................................................................... 5

Attributes of the Former Dam ................................................................................................ 7

The Conococheague Creek Stream Channel ........................................................................ 7

Reach 1: Downstream Reach .............................................................................................. 8

Reach 2: Riprap-lined Reach ............................................................................................. 12

Reach 3: Proximate Reach ................................................................................................. 13

Reach 4: Pool-Riffle Restoration Reach ........................................................................... 14

Reach 5: Upstream Reach .................................................................................................. 16

Former Reservoir Footprint .................................................................................................. 17

The Spoil .............................................................................................................................. 18

The Silt Cap ......................................................................................................................... 19

Wetland Development ...................................................................................................... 22

The Deltaic Deposit ............................................................................................................ 22

The Importance of the Birch Run Dam and Reservoir Site .............................................. 23

CHAPTER 3: REVIEW OF SIGNIFICANT LITERATURE .................................................. 25

Introduction ............................................................................................................................ 25

Key Concepts in Fluvial Geomorphology .......................................................................... 26

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Magnitude – Frequency Concept ..................................................................................... 26

Bankfull/ Effective Discharge Concept .......................................................................... 27

Stream Stability .................................................................................................................. 30

Fluid Shear Stress ............................................................................................................... 31

Critical Shear Stress ........................................................................................................... 31

Stream Power ...................................................................................................................... 34

Key Issues Concerning Earthen Dam Removals ............................................................... 35

Trapped Sediment Management ..................................................................................... 35

Protecting the Remaining Dam Infrastructure and Storing Spoil ............................... 37

Re-establishing Aquatic Habitat Diversity ..................................................................... 40

Hydraulic Modeling Approach: USACE HEC-RAS ......................................................... 41

Summary ................................................................................................................................. 43

CHAPTER 4: METHODS ......................................................................................................... 45

Introduction ............................................................................................................................ 45

Bathymetric Cross-section Surveying ................................................................................. 45

Floodplain Extraction and Model Construction ................................................................ 46

Flow Profile Discharge Estimation ...................................................................................... 47

Constructed HEC-RAS Models ............................................................................................ 49

Depth/Discharge Model Calibration .............................................................................. 50

Sediment Transport Capability Assessment ...................................................................... 51

Result Processing ................................................................................................................... 52

Pt. 1: Investigating the Bankfull Shear Stress within and adjacent to the Riprap-

lined Reach .......................................................................................................................... 53

Pt. 2: Flood Channelization Comparison for the Riprap-lined and Adjacent

Reaches ................................................................................................................................ 55

Pt. 3: Investigating the Hydraulic Effects of a Pool-Riffle Morphology Stream

Restoration on Bankfull Velocity, Shear Stress, and Stream Power ........................... 56

CHAPTER 5: RESULTS ............................................................................................................. 57

Introduction ............................................................................................................................ 57

Flow Data Estimation Method ............................................................................................. 57

Model Calibration Results: Assessing Model Accuracy ................................................... 61

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Sediment Transport Capability Assessment ...................................................................... 64

Flow Profile A ..................................................................................................................... 65

Flow Profile B ..................................................................................................................... 67

Flow Profile C ..................................................................................................................... 69

Flow Profile D ..................................................................................................................... 71

Flow Profile E ..................................................................................................................... 74

Summary ............................................................................................................................. 77

Pt. 1: Investigation of Bankfull Shear Stress within and adjacent to the Riprap-

lined Reach .............................................................................................................................. 80


Reaches .................................................................................................................................... 85

Pt. 3: Investigating the Hydraulic Effects of a Forced Pool-Riffle Morphology

Stream Restoration on Bankfull Velocity, Shear Stress, and Stream Power .................. 90

CHAPTER 6: DISCUSSION .................................................................................................... 106

Introduction .......................................................................................................................... 106

Notes about estimating stream discharge from sparse data.......................................... 107

Notes about calibrating the HEC-RAS model ................................................................. 110

Sediment Size Transport by Reach .................................................................................... 111

Flood Channeling ................................................................................................................. 113

Riprap Channel-armoring .................................................................................................. 116

Pool-Riffle Morphology Stream Restorations .................................................................. 117

CHAPTER 7: CONCLUSIONS ............................................................................................... 121

Introduction .......................................................................................................................... 121

Sediment Transport Capability Assessment .................................................................... 122

Reach 1 ............................................................................................................................... 122

Reach 2 ............................................................................................................................... 124

Reach 3 ............................................................................................................................... 125

Reach 4 ............................................................................................................................... 127

Reach 5 ............................................................................................................................... 128

Part 1: Bankfull Shear Stress, Stream Power, Flow Velocity, Slope, and Hydraulic

Radius Within and Adjacent to the Riprap-lined Reach ................................................ 129

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Part 2: Flood-channeling Capability of the Riprap-lined Reach ................................... 131

Part 3: Impacts of Pool-Riffle Morphology Stream Restorations .................................. 132

Significant Conclusions for the Practice of Dam Removal ............................................ 134

REFERENCES ........................................................................................................................... 140

APPENDIX A: Glossary ......................................................................................................... 146

APPENDIX B: Survey Benchmark Data ............................................................................... 149

APPENDIX C: Bathymetry Survey Cross-section Endpoint Data .................................... 150

APPENDIX D: Manning’s Roughness Values ..................................................................... 153

APPENDIX E: Cross-sectional Data ...................................................................................... 155

APPENDIX F: Pre-/Post-restoration HEC-RAS Modeling Results .................................. 233

APPENDIX G: Wolman Pebble Count Data ........................................................................ 262

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List of Figures

Figure 1: Watershed Background Map of the contributing drainage area of the 6 former Chambersburg reservoir Figure 2: Reach division map of the former Chambersburg reservoir study 8 area with Reaches 1 – 5 labeled Figure 3: Downstream Reach Photostation Image 10 Figure 4: Downstream reach bathymetry/woody debris survey diagram 11 Figure 5: Low-elevation UAV photograph of the riprap-lined reach (Reach 2) 12 Figure 6: Images of vane structures associated with the pool-riffle morphology 15 restoration within Reach 4 Figure 7: Log-structure location map for Reach 4 16 Figure 8: Manuel (2009a) reservoir bottom GPS mapping results 18 Figure 9: Image of silt cap push-core sample 21 Figure 10: Bankfull Discharge explanation diagram 29 Figure 11: USGS Gage (01614100 and 01614090) Photo Diagrams 51 Figure 12: Bedload Sediment Size Class Distribution Graph 58 Figure 13: Depth/discharge curve and modeled discharge level graph 62 Figure 14: Sediment Transport Capability Assessment Results: Flow Profile A 66 Figure 15: Sediment Transport Capability Assessment Results: Flow Profile B 68 Figure 16: Sediment Transport Capability Assessment Results: Flow Profile C 70 Figure 17: Sediment Transport Capability Assessment Results: Flow Profile D 73 Figure 18: Sediment Transport Capability Assessment Results: Flow Profile E 76 Figure 19: Sediment Transport Capability Assessment Summary Graph 78 Figure 20: Bankfull hydraulics of the riprap-lined reach: Part 1 results 81 Figure 21: Riprap-lined and downstream (Reaches 2 and 1) channel size 87 comparison Figure 22: Flow width/channel top width comparison graph 88 Figure 23: Reach 4 pre-/post-restoration modeling scenario minimum channel 92 elevation profiles Figure 24: Cross vane 4 and 5 detailed pre-post- restoration minimum channel 94 elevation profile Figure 25: Bank vane 7 pre-/post restoration minimum channel elevation profile 95 comparison Figure 26: Bankfull water surface comparison, pre/post restoration profiles 96 Figure 27: Bankfull velocity, pre/post restoration velocity profile comparison 98 Figure 28: Bankfull shear stress, pre/post restoration shear stress profile 100 comparison Figure 29: Bankfull stream power, pre/post restoration stream power profile 101 comparison Figure 30: Pre-restoration modeling results for Part 3: Bankfull hydraulics of the 103 riprap-lined reach

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Figure 31: Post-restoration results modeling results for Part 3: Bankfull 104 hydraulics of the riprap-lined reach Figure 32: Differences between instantaneous peak and daily mean discharge 109 data Figure 33: Size comparison image between Reach 1 and Reach 2 115 Figure 34: Detailed image diagram of a cross vane structure 118

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List of Tables

Table 1: Critical shear stress for median grain size of mixed sediments 33

Table 2: Bed material distribution data 59

Table 3: Results of the flow estimation method 60

Table 4: Model calibration results for the Conococheague Creek gage (01614090) 63

Table 5: Part 1: summary data for bankfull hydraulics of the riprap-lined and 81

adjacent reaches

Table 6: Bankfull flow transitions within the riprap-lined reach 84

Table 7: Comparison of mean daily discharge and instantaneous peak 108

discharge values

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ABSTRACT

A medium, earthen dam and a drinking water reservoir in the Valley-Ridge

Province were removed in 2005. After removal, riprap channel-armoring and a pool-

riffle restoration were applied to different areas of channel. Here, HEC-RAS was

used to assess erosional and depositional trends in stream reaches up- and

downstream of the former dam and reservoir, and to answer three research

questions regarding the two stream restoration methods. Part 1 of this study

compared bankfull hydraulic parameters of the riprap-lined reach to the reaches

immediately adjacent, Part 2 investigated the flood channeling capability of the

riprap-lined reach, and Part 3 investigated the implications of a pool-riffle

morphology restoration on hydraulic parameters within the affected reach and

downstream of the affected reach.

Major findings were: 1) the reach downstream of the former reservoir

produces the highest shear stress levels and appears to be relatively erosive, 2) the

riprap-lined reach produces low shear stresses and may be susceptible to deposition,

3) the riprap-lined reach is capable of containing floods up to 9.9 cms within its

banks, and 4) the pool-riffle system increases the variability of flow regimes within

the restored reach without impacting hydraulics of the adjacent, downstream reach.

Results from this work are applicable across the entire subjects of dam removals and

stream restorations, but would ideally be applied to other medium earthen dam

removals in wadable mountain streams having the need to be restored.

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CHAPTER 1: INTRODUCTION

Introduction

The damming of U.S. streams and rivers has occurred since colonial times.

Although the immediate economic effects were likely appreciated, the long-term

environmental effects were not well understood until fairly recently (Graf, 1999). In

terms of numbers, the ASCE (2013) reports there are 84,000 dams in the U.S., which,

when considered collectively, have earned an overall letter grade of “D+” in terms

of stability and safety. In 1988, when the ASCE began its assessment, the collective

dam infrastructure was given the letter grade “C.” Conclusively, over the years the

ASCE has noticed an increase in the overall number of deficient dams. With the

need to restore the biotic health of the country’s fluvial resources, this strongly calls

for dams to be reevaluated and in some cases removed.

According to the United States Army Corps of Engineers (USACE, 2013)

National Inventory on Dams (NID) Database, the peak of dam building in the

Appalachian Region occurred in 1965. That means more than half of the 6,744 dams

in the Appalachian region are older than the average design lifespan of 50 years.

Within the Valley & Ridge physiographic province alone are 944 dams with an

average age of 59 years. The average length and height of those dams are 230 meters

(756 ft.) long and 12.25 meters (40 ft.) tall as per the USACE NID (2013).

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The Birch Run Dam, prior to removal in 2005, was 72 years old, 20 meters (65

ft.) tall, and 213 meters (698 ft.) long. For comparison, it was 22% older, 38% taller,

and 7% less long than the statistical average dam in the Valley & Ridge

physiographic province. With its combined height and length, the Birch Run dam

was classified as a medium dam, which is important when considering removal

strategies and estimating ecological impacts of dams and dam removals (Graf, 1999).

Nationally, 1,185 dams have been removed since record keeping began; 665

(56%) since 1999 (American Rivers, 2014). The Commonwealth of Pennsylvania has

led the nation in the number of dam removal projects for each of the last 12 years

(American Rivers, 2014). Pennsylvania’s activity in dam removal reflects a number

of dynamic factors such as a rich human history, dam deterioration, suspected

ecological impacts, and monetary investment in the improvement of infrastructure.

Given the growing number of dams exceeding the average 50-year design lifespan

and the growing human interest in dealing with the ecological impacts of dams it is

likely that the apparent period of removing dams will continue, making the subjects

covered as part of this research significant for the future course of dam removals in

the Valley & Ridge province within the Appalachian Region.

Statement of Purpose

The purpose of this research is to enhance our shared understanding of some

of the effects of stream restoration work conducted following dam removal projects.

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Specifically, this work models and compares the shear stress, stream power and

extent of flooding produced at different levels of discharge flowing through the

former Birch Run Dam site. This study was conducted to; 1) determine if the riprap

armored reach may be affecting adjacent reaches, 2) detect any difference in the

degree of flood channelization between the riprap armored reach and adjacent

reaches, and 3) visualize how the utilization of a forced pool-riffle stream restoration

project applied to 750 meters (2460 ft.) of channel at the upstream extent of the

former reservoir effects slope, flow velocity, shear stress, and stream power.

This study is also being performed to advance the removal documentation

work of Johnston (2007) and post-removal surveys of Manuel (2009a, 2009b). The

work by Johnston (2007) documented the removal and restoration work performed

during the removal process. Manuel (2009a, 2009b) was first to document the site

following the removal/restoration work. Thus, this research will build on the results

of each study, and add to the general literature regarding dam removals and post-

removal stream restoration.

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Research Questions

To fulfill the above statements of purpose the following research questions

will be answered:

1. How do approximate bankfull measures of channel slope, hydraulic radius,

shear stress and stream power taken from the riprap lined reach compare

with measures taken from adjacent reaches?

2. How does flood channelization compare between the riprap lined reach and

the adjacent reaches?

3. How does the newly installed pool-riffle system at the upstream end of the

former reservoir affect bankfull measures of slope, shear stress, flow velocity,

and stream power of the restored reach and the adjacent, downstream reach?

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CHAPTER 2: STUDY AREA

Introduction

This section; 1) provides background on the contributing watershed, former

dam and study area, 2) summarizes the importance of the Birch Run Dam removal

site within the context of dam removal science, 3) presents Birch Run reservoir’s

initial state after removal, 4) introduces the relevant restoration methods (riprap

channel-armoring and pool-riffle stream restorations, and 5) presents the reach

divisions used for the completion of this study.

Characteristics of the Contributing Watershed

The Conococheague Creek has its headwaters on South Mountain and it

collects flow from the Birch Run, Knob Run, and Long Pine Run channels before

entering the former Chambersburg Reservoir area (Figure 1). With 111.8 cm (44.0 in)

of precipitation on average per year, the watershed upstream of the former dam

routes approximately 6.4 million cubic meters (1.7 billion gallons) of water per year

(Manuel, 2009a). The geology of the watershed supplies quartzite sediment to the

channels. Residing in South Mountain among predominantly the Weverton

Quartzite and Harpers Ferry Formation, material found in stream channels is likely

to have been sourced from one of these geologic units. Locally, ridges tend to be

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built from the more resistant Weverton unit, and slopes and valleys are usually

underlain by the poorly cemented, moderately fractured Harpers Ferry Quartz-

Sandstone unit (Fauth, 1968). The contributing area is covered by a thin mantle of

soil and is vegetated predominantly by hardwood forest (Manuel, 2009).

Figure 1: Watershed map of the contributing area (blue), channels (black lines), Long Pine Run Reservoir (light blue) and Former Birch Run Reservoir (tan). The total area of watershed is 13.8 square miles (35.7 sq. km) and is covered by mostly dense, hardwood forests. Underlying geology is predominantly quartzite covered by a thin mantle of soil. Data Sources: Orthophoto (USDA Ag. Imagery Program, 2013), Channels and Reservoirs (National Hydrography Dataset, USGS, 2005), Political Boundaries (US Counties)

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Attributes of the Former Dam

In regard to the size and shape of the former dam and reservoir, the Birch

Run Dam was a 19.8-meter (65-foot) tall earthen dam spanning 213 meters (700 feet)

of valley bottom that was constructed in 1933 to provide the Borough of

Chambersburg with drinking water. This combination of size and shape leads to the

dam being classified as a medium dam. The dam impounded a storage volume of

6,800,000 cubic meters (2.4 x 108 cubic feet) at a maximum pooling depth of 17.4

meters (57 feet). The reservoir covered a 1,150-meter (3,760-ft.) length of valley

bottom and 21.7 hectares (53.6 acres) of valley area. With the draining and removal

of the dam, this length of former reservoir bottom was exposed and subjected to

more natural fluvial conditions.

The Conococheague Creek Stream Channel

This study divided reaches of the Conococheague Creek based on their

restoration treatments and location in regard to the former dam/reservoir footprint.

These reaches will be known further in this report as reaches one thru five. Their

locations are seen in Figure 2 along with the modeled cross-sections (green), and a

table of the cross-section numbers representing each reach. The following

paragraphs further describe each of the reaches in Figure 2.

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Figure 2: Reach Division Map of the former Chambersburg Reservoir study area and modeled cross-sections (green). Bank stations are seen as red points. Cross-section numbers are presented, as is a table summarizing each reach’s cross-sections. Reaches were given arbitrary numbers 1 thru 5, each signifying a location in relation to the former dam/reservoir or a specific channel treatment. For example, Reach 1 is the reach downstream of the former dam, yet upstream of the former spillway. Reach 2 is the reach within the existing dam abutments. Reach 3 is the proximate reach between the riprap and restored reaches. Reach 4 is the reach that was restored in 2013 using a pool-riffle morphology restoration technique. Reach 5 is the reach upstream of the former reservoir area, but downstream of the confluence of the Conococheague and Birch Run Streams

Reach 1: Downstream Reach

Reach 1 is a segment of channel that is downstream of the riprap-lined reach

(and former dam) but upstream of the former intersection of the spillway and

Conococheague Creek stream channel. Reach 1 extends from just downstream of the

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riprap-channel lining, which armors the remaining dam abutments, to just upstream

of the first channel division downstream (seen in Figure 5 below). Being

downstream of the former dam, yet upstream of the spillway’s connection with the

historic Conococheague Creek, this portion of channel was only subjected to

discharges that were let through the dam’s main drainage pipe while the dam was

in operation. This means that this portion of channel had not seen natural

streamflow or sediment regimes for 72 years prior to the dam’s removal, and was

only subjected to discharges above baseflow during reservoir drawdowns.

Now, this reach is still heavily vegetated with abundant woody debris

damming the channel and root structures forming many of the stream banks.

Mountain Laurel, mosses, ferns, and large hardwoods predominate the floodplains

and a few boulders are found in the channel. Figure 3 shows an image of the

downstream reach that was photographed during the spring of 2015. Visible in this

image are many downed trees, woody debris, a layer of sand deposited on the

floodplain (at image right), and poorly defined banks.

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Figure 3: Representative image of the downstream reach (Reach 1 in Figure 2). Image captured from a photostation just downstream of the riprap-lined reach, looking downstream (see Figure 5 for photostation location). Labeled is flow direction (blue arrow), woody debris, and sand-sized deposition on the floodplain at image left. This reach represents a portion of channel that was hydrologically inactive for 72 years while the dam was in operation. So, it is likely that this reach may be subject to geomorphic change following the dam’s removal. (Photo: May, 2015)

The location of the photostation (used to capture the image in Figure 3) in

relation to the riprap lined reach and cross-sections are seen below in Figure 5. The

photostation image was placed to capture a representative snapshot of the current

appearance of this reach that is just downstream of the riprap lined reach’s last

cross-section (cross-section 28). The location was chosen to capture the current state

of the portion of the channel that was reactivated after the dam’s removal, and

investigate the possible impacts of the upstream riprap armoring.

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The significance of Reach 1, being downstream of the dam but upstream of

the former spillway (and now being reactivated), led to a more detailed mapping

initiative being taken within this reach. This included photo mapping of the reach,

noting bar/pool, boulder, and woody debris locations from the end of Reach 2 to the

former spillway’s intersection with the Conococheague Creek stream channel. The

results of the channel mapping project is seen in Figure 4. Woody debris appears as

brown symbols in Figure 4, and each piece of woody debris was classified as being a

root structure, brush, or small, medium, or large woody debris. The debris is seen in

abundance throughout this reach, and much of the large material appears to be

sourced from the banks within the reach.

Figure 4: Results of a photo-mapping exercise within Reach 1, extending downstream to the location of the former spillway (top right). Labeled are; the modeling cross-sections (XS 22 thru XS 29), the representative photostation for Reach 1 (yellow triangle), flow direction, an inactive channel. Woody debris is seen as brown lines (trees) and root-structure symbols (also brown), and was classified as root structures, brush, or small, medium, or large woody debris. The sandy deposit is shown as white/tan area on southern banks of cross-sections 27 thru 23. Green hatch-marked areas within the channel boundaries downstream of cross-section 22 represent vegetated floodplains. Sand/gravel bars and banks are seen as white/gray dotted areas.

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Reach 2: Riprap-lined Reach

Just upstream of Reach 1 is Reach 2 (see Figure 2), the riprap-lined reach.

After dam breaching and removal were completed, the portion of channel between

the still-standing abutments was armored with limestone riprap boulders to abate

any lateral channel erosion that would threaten to erode earthen fill material still

contained in the remaining dam structure (Johnston et al., 2007). This riprap-lining is

seen in Figure 5 from drone photography taken in summer 2014.

Figure 5: Low-elevation UAV photograph of the riprap-lined reach (Reach 2 in Figure 2) of channel that protects the remaining dam abutments from erosion during flooding. Labeled are the areas of riprap armoring, flow direction, and the remaining portions of the dam. Armoring was completed as part of the dam’s removal project. The riprap-lined reach is 150 meters (465 ft.) in length, has a slope of 14 m/km and a large bankfull volume for channeling floods (Photo credit: Dr. Scott Drzyzga, Summer 2014)

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In total, 150 meters (465 feet) of channel was lined on bed and banks to keep

the remaining abutments from eroding. This reach has an average slope of 14 meters

per kilometer (74 ft./mi.) of channel compared to 12.9 meters per kilometer (68.1

ft./mi.) in Reach 3 (the proximate reach) and five meters per kilometer (26.4 ft./mi.)

within the downstream Reach 1. This reach is important because its geometry and

armoring are meant to protect the existing dam infrastructure from erosion, and to

date, the limestone riprap has successfully kept the channel from laterally eroding

into the remaining portion of the embankment, as per its design goal.

Reach 3: Proximate Reach

Reach 3 in Figure 2 is the Proximate Reach, the reach between the riprap-

lined reach and the stream restoration. This channel was submerged by the reservoir

when the dam was in service. When the Birch Run Dam was initially built in 1933, a

portion of this reach was purposefully filled with sand to divert the channel through

the dam intake. Upon dam removal in 2005, 229.4 cubic meters (8100 cubic feet) of

sand was removed along 61 linear meters (200 feet) of channel within this reach

during restoration of the channel to its natural path. The goal of this was limit the

potential for the transport of sediment from within the reservoir area (Johnston et

al., 2007).

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There are two significant sediment-related concerns within Reach 3. Within

Reach 3, on the northwest floodplain, the silt cap that was deposited during the

dam’s operation is present, and the floodplain on the southeast bank now stores the

spoil. The silt cap covers most of the bottom of the former reservoir within Reach 3.

The spoil material is spread along the southeast valley wall throughout the entire

length of this reach. These two features are covered in greater detail later in this

section (see sub-sections titled “The Silt Cap” and “The Spoil” under the section

“Former Reservoir Footprint”).

Reach 4: Pool-Riffle Restoration Reach

Reach 4, at the upstream end of the reservoir footprint underwent a pool-

riffle morphology stream restoration project in 2013. This work constructed a series

of pool and riffle-simulating log vane structures along 750 meters (2460 ft.) of the

channel to improve in-stream habitats for Brook Trout (Trout Unlimited, 2012). The

restoration installed a total of seven upstream-pointing log vanes, seven side

deflectors, and one perpendicular log vane (each structure is presented in Figure 6).

From measurements taken in 2015, the average spacing of riffle-simulating

structures is 50 meters (164 ft), and the average pooling depth behind each log is 0.4

meters (1.3 ft) from the bottom of the pool to the top of the log.

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Figure 6: Images of each of the types of pool and riffle simulating structures used as part of the forced-pool riffle morphology stream restoration throughout Reach 4 of the study area. Left image shows one of the seven upstream pointing log vanes, the center image shows two of the seven side-deflectors (bank vanes), and the right image shows the single perpendicular log vane installed at the site. White arrows signify flow direction. Notice sandy deposits (light tan areas) behind both the cross vane (left) and bank vane (center). This shows the sediment trapping qualities of each of these structures (Photos: June 2015)

So, seven upstream pointing cross vane structures, seven bank vanes, and one

perpendicular cross vane structure were installed in Reach 4 during 2013. The

location of each of these structures in Reach 4 is presented in Figure 7 below.

Structures are labeled as CV-1 thru CV-7 for cross vanes, BV-1 thru BV-7 for bank

vanes, and Perp. Vane for the perpendicular cross vane. Each of the structures is

meant to imitate natural stream channel morphology bedforms by controlling the

shape of the bed around the structure.

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Figure 7: Location map of log structures associated with the pool-riffle morphology stream restoration within Reach 4. Image shows the mapped vane structures of the surveying work done in summer of 2015. Vanes (in red) are labeled BV and CV for bank and cross-vane, respectively. The installation of vanes results in an average pool spacing of about 50 meters (164 ft.) through the reach and increases the diversity of in-stream environments through simulating pools and riffles in the reach. Pools create areas for fish to rest and sands to be deposited, while riffles comprise areas of coarse sediment deposits.

Reach 5: Upstream Reach

Reach 5 is the reach upstream of the former reservoir but downstream of the

confluence of the Conococheague Creek and Birch Run. It is represented in

modeling by 15 cross-sections, cross-sections 152 thru 166. This reach was upstream

of the former reservoir footprint, and it is likely that this reach of channel has not

been significantly influenced by the presence of the Chambersburg Reservoir

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downstream. Of the reaches throughout the study area, this reach may be the most

‘natural’ of the five. This reach was never inundated by the reservoir, and (referring

to the presence of both a deltaic and silt cap deposit) was capable of transporting

sediments into the reservoir during its operation. This reach now displays natural

pools and riffles, some large woody debris and boulders.

Former Reservoir Footprint

Within the former reservoir footprint exists several features that may, over

time, appear to be typical features associated with earthen dam removals. The

location of these features within the former reservoir footprint is significant when

determining the interaction of each of the features and flooding. The most important

of the features, presented in Figure 8, are the silt cap that was deposited behind the

dam during its operational period, the spoil pile, wetland, and remaining dam;

which are labeled. Features are discussed further in the following paragraphs.

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Figure 8: Map of the former reservoir bottom and significant features such as the remaining dam (red), silt cap (light blue), wetland (white/blue hatching), spoil (brown), and delta deposit (yellow). Labeled are Reaches 1 thru 4, as well as the locations of the remaining dam, silt cap, wetland, and spoil. Flow direction is labeled with the blue arrow. The features highlighted here may prove to be common occurrences following earthen dam removals, so their location and apparent interaction with flooding is important to the science behind dam removals. Note the presence of silt cap and spoil placed on the floodplains of Reach 3.

The Spoil

During removal, when the portion of dam was de-constructed, more than

60,000 cubic meters (2 million cubic feet) of material, or spoil, was taken from the

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breach. Most of this material was reworked soil, gravel, and cobbles, and is now

stored in three locations at the site: 1) in and over the concrete spillway and former

intake tower, 2) atop the former dam, and 3) along the southeast rim of the former

reservoir basin (Johnston et al., 2007) (Figure 8). Spoil is contained along a majority

of the southeast floodplain length within Reach 3. The spoil was purposefully

placed outside of the 15-year flood line (Johnston et al., 2007). No major signs of

erosion of the spoil deposits have been observed during multiple reconnaissance

missions at the site.

The Silt Cap

The Conococheague Creek carried suspended sediment into the reservoir

during the operational period of the dam. This sediment, seen as the fine-grained

layers in Figure 9, was deposited at the bottom of the reservoir behind the dam.

Repeated coring at locations behind the dam (after dam removal) has revealed

clayey, silty, and fine sandy deposits at many locations. Manuel (2009a) mapped the

‘silt cap’ deposited behind the dam and reported that it is generally thin (5-10 cm, or

1.9 - 3.9 inches), but can be much thicker in other reservoirs. As expected, silt cap

thickness tends to increase with proximity to the dam, and in areas of greater

reservoir depth.

20

On multiple occasions, push-core core samples have revealed a cohesive

sequence of fine layers of clayey and silty material that exhibits a conspicuous

change in color (Figure 9). It is hypothesized (but not tested here) that the

discontinuity between the subsequence of dark-colored layers and the subsequence

of light-colored layers marks the effect that construction of the Long Pine Run dam

(1970) had on the sediment supply regime. A break in color of this type of

symbolizes another way that dams can fragment sediment supply in watersheds.

21

Figure 9: Image of push-core sample collected from within the former reservoir, near the base of the former Birch Run Dam. Four distinctive layers are noted within the core. The bottom layer is organic-rich topsoil and partially decomposed woody material representing the top of the historic valley bottom prior to inundation. Above this, the 8.5 centimeter (3.3 in.) thick silty layer likely represents suspended material deposited during the dam’s service period. The uppermost layer is detritus developed after the removal of the dam and is the current forest floor. Given the duration of operation (72 years), sedimentation in this area of the reservoir was approximately 1 cm/decade (0.39 in./decade) or 1 mm/year (0.039 in/yr.) Although clay and fine-grained silt dominate sediments deposited, this is a low sedimentation rate and likely reflects the lack of clay-producing parent rocks within the weathering reaches of the watershed. (Photo: June 2014)

The thickness of fine sediment seen in Figure 10 above displays that this area

of the reservoir had a sedimentation of 1 cm/decade (0.39 in./decade) in this reach.

This low rate of sedimentation likely points to the lack of clay-producing geology in

the eroding reaches of the upstream watershed and that the watershed has no major

development (only private residences).

22

Wetland Development

Within Reach 3 (refer to Figure 2), soon after the dam was drained a

wetland/bog formed on the northwest side of the channel, and smaller wetlands

have formed at other locations within the former reservoir footprint (see Figure 8)

(Manuel, 2009a). The large wetland at the site collects surface flow from the hill to

the northwest of the former reservoir area, and PA-233. Some of this flow is

funneled through a culvert that empties just up-valley of the embankment (seen as

dark blue polygon in Figure 8), and enters the wetland (labeled in Figure 8). It is

also suspected that a portion of flow supplying the large wetland comes from

underground, through small valley bottom springs, but this is not investigated here.

There is one primary location that the wetland empties into the main channel prior

to proceeding through the former dam.

The Deltaic Deposit

At the upstream extent of the former reservoir (the upper end of Reach 4 in

Figure 2) the channel carries water over a deltaic deposit of cobbles, gravel, and sand

that was deposited at the upstream end of the reservoir during its operational

period. The extent of the deltaic deposit is seen as the yellow polygon in Figure 8.

The reach of stream flowing through this deltaic deposit, prior to restoration in late

2013, was void of natural pool and riffle sequences. Although the amount of

23

sediment deposited in this area of the reservoir is relatively small, any sediment

deposited would raise elevations of the floodplains in relation to the channel

bottom.

The Importance of the Birch Run Dam and Reservoir Site

What is learned from this study can be directly applied to other dam removal

scenarios. To make this easier, important factors in this dam removal are outlined

here and two dams that are currently emptied and to-be-removed are highlighted

because, again, what is learned from this study is very applicable in others.

As described above, much of the upstream catchment area is underlain by

quartzite or quartzite-sandstone materials, which are relatively erosion resistant.

The upstream catchment area is covered predominantly by forest, which generally

stabilizes and inhibits transport of the relatively thin mantle of soil that does exist.

These physical factors, combined, allowed a relatively small volume of sediment to

become trapped behind the dam during its operational period. That said; the long

and steep valley walls that constrained the sides of the former reservoir also

provided dam removal engineers with very little room to safely store the spoil in the

former reservoir basin and outside the floodplains of the restored stream channel.

These spoil deposits and in-situ lacustrine deposits can become mobilized whenever

the stream floods during large storm events.

24

The observations documented at the former Chambersburg Reservoir site and

the lessons learned during this study can be used as reference points and applied

during efforts to study other dam removal sites in the region. For example, the

Meadow Grounds Dam and Lake (Fulton County, PA) is situated along a linear

valley with an undeveloped contributing watershed, with quartzite-dominant

geology. Similar to Birch Run, the Meadow Grounds Dam is another medium

earthen dam that was also recently drained to mitigate some safety issues regarding

the dam.

The Gunter Valley Dam and Reservoir (Franklin County, PA) is another

example of a linear, valley reservoir in which the reservoir was recently drained and

the dam will soon be removed (PA DCNR, 2013). Again, this watershed area was

largely undeveloped and had a geology that was largely quartzite-dominant. The

Gunter Valley Dam is another example of a medium earthen dam. So, it is likely that

these former reservoir footprints have similar sedimentation rates and may be

similarly shaped. So, study of the Birch Run Dam and Reservoir site can serve as a

valuable benchmark for other dam removal and stream restoration work at the

Meadow Grounds and Gunter Valley sites as at other sites across the Appalachian

Highlands.

25

CHAPTER 3: REVIEW OF SIGNIFICANT LITERATURE

Introduction

Fluvial geomorphic processes and their resulting morphological forms are

“driven by a balance of driving (e.g. channel gradient and discharge) and resisting

(e.g. bed and bank resistance to transport) forces” (Bizzi and Lerner, 2015: p16).

Stream discharge, transported sediment volumes, and sedimentation rates can be

very difficult properties to measure accurately and precisely in all field conditions,

especially during very short or extreme weather events, so multiple similar but

different measures have been developed over time to foster the work of fluvial

geomorphologists.

To outline some of these topics this section will review relevant literature

regarding; 1) key concepts in fluvial geomorphology, 2) the key issues and goals

concerning earthen dam removals and some of trends used to address those issues,

and 3) some common hydraulic modeling approaches for studying fluvial

geomorphology and monitoring dam removal and stream restoration project sites.

26

Key Concepts in Fluvial Geomorphology

The text below explains some of the larger concepts of fluvial geomorphology

that come into play when researching streams and rivers such as; 1) the magnitude –

frequency concept, 2) the concepts of bankfull and effective discharges, 3) stream

stability, 4) fluid shear stress, 5) critical shear stress, and 6) stream power. This

review is important in understanding the methods applied in this work, and

highlights relevant literature in the subject of fluvial sciences, channel hydraulics,

and sediment transport.

Magnitude – Frequency Concept

The magnitude-frequency concept pertains to the magnitude of and the

frequency of discharge events in a stream channel. Although high magnitude-low

frequency discharge events can cause substantial geomorphic change to a stream

system, moderate magnitude-frequent flows typically cause the most geomorphic

change over time (EPA, 2012). The reason for this is that low magnitude-high

frequency events typically carry very small amounts of sediment, and high

magnitude-low frequency events do not occur frequently enough to successfully

form and maintain channel shape (Wolman and Miller, 1960).

27

Essentially, the geometry of river/stream channels is most largely controlled

by the frequent/moderate flows that transport the greatest volumes of sediment

over time and occur frequently enough to maintain the shape of the channel

(Wolman and Miller, 1960). In this study, a range of discharge scenarios was

modeled to find the hydraulic properties of bankfull and larger flood events. The

specific range selected in this work was informed by historic stream discharge data

that were collected just upstream of Reach 5 at two USGS stream gages and

sediment size distribution data collected over a four-year period by students

enrolled in a field course.

Bankfull/ Effective Discharge Concept

‘Bankfull stage’ and ‘bankfull discharge’ are measures of maximum stream

elevation and maximum discharge that are contained within stream channel banks

(Dunne and Leopold, 1978; Richards, 1982; Simons and Senturk, 1992; Thorne et al.,

1999). According to Dunne and Leopold (1978: p818):

"The bankfull stage corresponds to the discharge at

which channel maintenance is the most effective, that is,

the discharge at which moving sediment, forming or

removing bars, forming or changing bends and

28

meanders, and generally doing work results in the

average morphologic characteristics of channels."

Dury (1976), Leopold (1964), Rosgen (1996), and Johnson (1999) studied many

types of streams and reported that return intervals for bankfull discharge events are,

on average, between 1.2 and 2.0 years, which suggests that bankfull discharge events

are important but not rare events. Perhaps explained best by a diagram, a cross-

sectional view of a stream channel at the bankfull discharge level is presented in

Figure 10.

29

Figure 10: Cross-sectional diagram of; less than bankfull discharge (a), bankfull discharge (b), and greater than bankfull discharge (c). In each, the brown line represents the stream channel profile and blue line denotes water surface. The blue triangle and short horizontal line denote water surface. Bankfull discharge is the discharge level at which the channel is filled to the top of the apparent banks (but does not flood). In HEC-RAS banks were noted by locating bank stations at the apparent location of the top of the stream channel geometry. Bankfull discharge within Reach 5 (the most natural reach of stream within the study area) was selected as the bankfull discharge for modeling, and was determined to be 3.02 cms (106.8 cfs).

Effective discharge is the rate of streamflow that transports the most sediment

over time (EPA, 2012). The effective discharge concept may seem similar to the

bankfull discharge concept, but effective discharge is revealed through the collection

of both stream flow and sediment transport data so that a more complete sediment

rating curve may be established (Andrews, 1980). One advantage of using effective

30

discharge measures instead of bankfull discharge measures is that effective

discharge takes into account both sediment transport and discharge, the two

controlling factors on the morphology of the stream system (Johnson, 1999).

Stream Stability

A stable stream was first defined by Davis (1902) and it means a stream

condition of balance between sediment erosion and deposition. A stream having

unbalanced sediment erosion and deposition is therefore considered unstable

(Davis, 1902). The concept of stream stability has been well-developed within the

science of fluvial geomorphology and has been studied in many different ways.

Some studies use modeling to predict net erosion/deposition through estimators

like fluid or critical shear stress, stream power, or velocity.

Stream stability can be estimated be comparing levels of fluid shear stress and

the critical shear stress of the dominating bedform-controlling sediment. When

floods occur, fluid shear stress levels great enough to transport bedform-controlling

sediments may occur. Where these sediments are deposited after the flood event will

then dictate channel bed-shape until the next flood event.

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Fluid Shear Stress

Shear stress refers to the frictional force of water flowing down-slope and

pulling on the walls and bed of the channel. Shear stress is an input parameter in

models used for estimating sediment transport rates and maximum transportable

sediment size. Ever since Shields (1936), scientists have modeled the transportation

of sediments in streams using a balance between the shear stress of flowing water

and the gravitational force keeping particles in place on the stream bed (e.g., Miller

et al.,1977; Parker et al., 1982; Parker et al., 1990; and Cui and Wilcox, 2008).

Critical Shear Stress

The critical shear stress is defined as the level of fluid shear stress required to

initiate motion of a given size, shape, and density of sediment within a stream

channel. So, when the fluid shear stress exceeds the critical shear stress for a given

sediment size-class, that given size of sediment will enter transport. Shields (1936)

first reported on the concept of incipient motion of bed particles, the idea of a critical

(minimum) level of fluid shear stress required for initiation of particle motion

(although this work was completed in a lab flume with uniform, non-cohesive

sediments). Fischenich (2001) used the original concepts of Shields (1936) and re-

worked equations to include the angle of repose in numerical estimations of critical

shear stress for various sediment size classes.

32

This work was applied in 2008 by USGS scientists, who improved upon the

work of Shields by incorporating mixed sediment sizes into numerical estimates.

Numerically, this estimate is:

𝜏𝑐 = 𝜃∗(𝑠 − 1)𝜌𝑔𝑑50 (Eq. 1)

where… 𝜏𝑐 is critical shear stress, 𝜃∗is the dimensionless Shields parameter for the given median particle size, s is the specific gravity of the sediment particles, 𝜌 is the density of water, g is the constant acceleration of gravity, and 𝑑50 is the median particle size of the bed material.

The results of this work are seen in Table 1 below, evaluated for various

sediment sizes that are common in natural stream channels and rivers. Methods of

Berenbrock and Tranmer (2008) evaluated the above equation for sediment sizes

ranging in size from coarse cobbles of 128 millimeters (5 in.) and greater in diameter,

to medium silt of 0.015 millimeters (0.001 in.) and greater in diameter. Associated

with coarse cobbles and medium silt-sized sediments are respective critical shear

stresses of 112 N/sq. meter (2.3 lb./sq. ft.) and 0.06 N/sq. meter (0.001 lb./sq. ft.).

33

Table 1: Median sediment size classes and associated critical shear stress levels from Berenbrock and Tranmer (2008). Sediment sizes, associated sediment sizes, critical shear stress and critical flow velocity are presented. Each of the size classes listed represent the dominant sediment class size in a sample of sediment. For each of these median diameters, when the fluid shear stress of channel flow exceeds the critical shear sediment dominated by that class of sediment will be transported. Sediment classes range from medium silts to coarse cobbles, and range in size from 0.015 mm (medium silt) to 128 mm (coarse cobbles).

Critical Shear Stress Required to Move Various Sediment Sizes (from Berenbrock and Tranmer, 2008)

Class Sediment Size (in)

Sediment Size (mm)

Critical Shear, N/sq m (lb/ft2)

Critical Flow Velocity, m/s

(ft/s)

Cobble Coarse > 5 > 128 112 (2.3) 0.33 (1.1)

Fine > 2.5 > 64 54 (1.1) 0.23 (0.7)

Gravel

Very Coarse > 1.3 > 32 26 (0.5) 0.16 (0.5)

Coarse > 0.6 > 16 12 (0.2) 0.11 (0.4)

Medium > 0.3 > 8 5.7 (0.1) 0.07 (0.2)

Fine > 0.16 > 4 2.7 (0.05) 0.05 (0.2)

Very Fine > 0.08 > 2 1.3 (0.03) 0.04 (0.1)

Sands Very Coarse > 0.04 > 1 0.47 (10x10-2) 0.02 (0.06)

Coarse > 0.02 > 0.5 0.27 (5x10-3) 0.02 (0.06)

Medium > 0.01 > 0.25 0.19 (3x10-3) 0.01 (0.03)

Fine > 0.005 > 0.13 0.15 (3x10-3) 0.01 (0.03)

Very Fine > 0.003 > 0.063 0.11 (2x10-3) 0.01 (0.03)

Silts Coarse > 0.002 > 0.031 0.08 (1x10-3) 0.01 (0.03)

Medium > 0.001 > 0.015 0.06 (1x10-2) 0.01 (0.03)

So, for each of the sediment sizes seen in Table 1, if fluid shear stress levels

present in a stream channel exceed the critical shear stress levels of each of the

sediment types that sediment will be transported. For example, a fluid shear stress

of 10 N/sq. m. (0.18 lb./sq. ft.) would initiate transport of sediments classified as

medium gravels and smaller (smaller than 8 inches) which only requires 5.7 N/sq.

m. (0.10 lb./sq. ft.). The “Sediment Transport Capability Assessment” portion of

34

this study assesses the maximum sediment size capable of being transported at

bankfull discharge in relation to the critical shear stress levels presented in Table 1.

Stream Power

Another stream stability estimator is stream power. Stream power is “a

measure of the main driving forces acting in a channel and determines a river’s

capacity to transport sediment and perform geomorphic work” (Bizzi and Lerner,

2015: p16). Bagnold (1980) defined the term more specifically as the mean rate of

kinetic energy supply and dissipation along a stream channel, which can be used to

predict erosion.

Lopes (2001) tested seven different bed load transport equations and found

the Bagnold method of estimating sediment transportation using information about

stream power was the most accurate. A few years earlier, however, Gomez and

Church (1989) tested twelve bedload sediment transportation equations for 410

bedload events and found that none of the equations performed consistently

because of finite data limitations and sediment transport process complexity. The

present author recognizes Gomez and Church’s warning and is aware that fluvial

systems performing geomorphic work are very complex systems that cannot be

modeled completely (yet).

35

Key Issues Concerning Earthen Dam Removals

This section reviews key issues pertaining earthen dam removals such as;

trapped sediment management, protecting remaining infrastructure, and re-

establishing aquatic diversity. Each of the topics, though reviewed at here in regard

to earthen dam removals, may be applied amongst dam removals of many different

settings and scenarios.

Trapped Sediment Management

Perhaps the most challenging aspect of dam removals is the sediment that is

exposed after reservoirs are drained (ASCE 1997; Graber et al. 2001; Hart and Poff

2002; Downs et al. 2009). Newly exposed sediment that was once trapped at the

bottom of a reservoir becomes available to erosion and transport as floodplains and

stream channels are reestablished through former reservoir areas. Large sediment

volumes and contaminated sediments present threats to downstream channel

equilibriums when they are transported. Modeling by Cui (2003; 2006b; 2007; 2011)

determined that, in some cases, sediment released after dam removal can cause

channel aggradation up to 10 kilometers (6.2 miles) downstream of the former dam.

Following proper environmental assessments, newly exposed sediment is

typically managed according to a dam removal plan. The most common sediment

36

management strategies are: 1) allowing the stream or river to naturally erode and

transport the sediment; 2) removing only the sediment that is within the anticipated

path of the stream or river while leaving the remaining sediment in place; or 3)

removing all the sediment from the former inundated area (Wunderlich et al. 1994).

Cost tends to increase with each truckload removed. Regardless of the sediment

management strategy, staged drawdowns/removals can be a useful method of

ensuring that sediment is dewatered and stabilized before removal. The staged

drawdown/removal strategy also minimizes the resuspension of potential

pollutants (Quinn, 1999).

Following dam removals, the long-term management of sediment is also

important. One of the most common ways of managing this sediment is through re-

vegetation of the formerly inundated area. Re-establishing vegetation in the

inundated area helps to anchor sediments that are accessible on the channel’s

floodplains. In some cases formerly inundated areas have been known to re-vegetate

themselves, but the susceptibility of those areas to invasive species has been

recognized in the past (Quinn, 1999). Strategically modeled plantings can be planned

by referring to unaltered stream banks up and downstream of the former

impoundment. This sort of strategy minimizes the likelihood of invasive species

establishing any dominance within the formerly inundated area.

One exemplary case of sediment management is centered on the restoration

of the Elwha River in Olympic National Forest, Washington. The removal of two

37

massive dams, the Elwha Dam and Glines Canyon Dam, was key in restoring

anadromous fish species throughout the Elwha basin. The two dams, accumulating

almost 13.8 million cubic meters of sediment over their operational periods were the

first examples of the U.S. Federal Government purchasing dams for the purpose of

removing them. In the removal of these two dams the lateral migration of the river

channel was not expected to occur over the entire reservoir width, so a portion of the

accumulated sediment was allowed to remain within the newly exposed reservoir

bottoms. With goals of restoring natural floodplain ecosystems and stabilizing

trapped sediments, re-vegetation of each of the reservoirs was planned by first

surveying native species throughout the Elwha River basin as a means to combat the

introduction of invasive species to the restored ecosystem (NPS, 2011).

Protecting the Remaining Dam Infrastructure and Storing Spoil

Unique in the case of some earthen dam removals, in which a portion of the

dam is left intact, is the need to protect the remaining infrastructure from erosion

during flood events. Another unique aspect of earthen dam removals is the storage

of spoil material that is removed from the former dam as part of, or the entire dam is

being removed. Partial removals and storing spoil material on-site helps reduce the

total cost associated with removing dams and minimizes the impact of the removal

(Johnsten et al. 2007).

38

Armoring banks of streams or rivers is one common method of laterally

stabilizing stream banks and prohibiting erosion (Reid and Church, 2015). This

makes the application of riprap channel armoring one popular method for

protecting any remaining infrastructure following the partial breaching of earthen

dams. Some researchers claim that riprap armoring improves in-stream habitats in

previously disturbed streams (Binns, 1994; Craig and Zale, 2001; Schmetterling,

2001) but others claim that riprap armoring can have unintended morphological

impacts that can affect habitats (Quigley and Harper, 2004; Reid and Church, 2015).

The short-term morphological impacts are not likely to extend great distances

up or downstream (Reid and Church, 2015). The placement of large bank armoring

material on the outer bank of a channel will impact local and downstream sediment

transport rates. Typically, in unstable streams, sediment is eroded from the outer

bank of bends and is deposited in the next riffle downstream (Church, 2010; Reid

and Church, 2015).

When the outer bank is armored, sediment cannot be eroded from this

segment of the channel. Often, a reduction in sediment supply in one segment of

channel may cause sediment entrainment from another location. Depending on the

size of the stream/river, the erodibility of the channel margins, and the rate of bed

material transport in the fluvial system; the time period in which impacts will occur

is likely to vary between a couple years to centuries (Reid and Church, 2015).

39

Storage of spoil material is another key issue of earthen dam removals. The

spoil that was once contained within the earthen dam presents another potential

source of sediment contamination to the channel after the dam’s deconstruction.

Storage of spoil on site is a cost-reducing method when removing dams (Johnston et

al., 2007). Johnston (2007) detailed the handling of the spoil at the former

Chambersburg Reservoir site. In this case the spoil was placed around the southeast

rim of the former reservoir at an elevation that wouldn’t be inundated by the 15-year

recurrence interval discharge.

Regarding the former Chambersburg Reservoir, Johnston (2007) also reported

some of the other benefits of storing spoil on-site. A portion of the spoil was used to

backfill the remaining spillway and abandoned control tower. Filling the spillway

with spoil eliminated the fall and drowning hazard due to steep walls and

eliminated a driving hazard along an interstate (PA-233). Filling the abandoned

control tower with spoil eliminated the possibility of human access, thusly

eliminating any associated risk. Also to protect the channel from potential sediment

contamination, the remaining riprap armored portions of the dam were covered

with two feet of spoil and seeded (Johnston et al. 2007).

40

Re-establishing Aquatic Habitat Diversity

One common goal of dam removal projects is to re-establish habitat diversity

in reaches of stream that had once been blocked by dams. Following removals,

stream restoration projects may aid in repopulating reaches of fluvial systems that

were once blocked and flooded by dams. Annually, the U.S. spends over $1 billion

on stream restoration projects, but unfortunately only 10% of total projects receive

post-completion monitoring (Bernhardt et al., 2005; Buchanan et al. 2010).

The Potomac Watershed Restoration program of the Chesapeake Bay

Foundation is a collaborative effort to restore the health of land and water of the

Potomac River Basin. Using the 2010 Chesapeake Clean Water Blueprint, two areas

of south-central Pennsylvania were identified as areas with significant need for the

planting of the riparian buffers in attempt to improve water quality. The two areas

that were identified as priorities were the Potomac watershed portion of Franklin

County and the Antietam Creek Watershed (Chesapeake Bay Foundation, 2015).

These are two local examples of focused efforts to restore health to headwaters of the

Chesapeake Bay. Although not directly mentioned, the Conococheague Creek in

Adams County, PA is also a headwater of the Chesapeake Bay.

One common method of restoring channels to more natural states is the

simulation of pools and riffles. Pools and riffles are natural channel geometries that

lotic biota have evolved to prefer. This fact points to why pool and riffle simulating

41

stream restorations are capable of supporting diverse biological communities. One

project on the Beaver Creek in Knox County, East Tennessee restored a reach of

stream impacted by urbanization and loss of pool-riffle morphology. This project

saw a reversal (decrease) in shear stresses between low- and high-flows post-

restoration, and flow deceleration due to the installation of pools and riffles

(Schwartz et al., 2015). Although this study regards an urban stream, the

constrained, straightened channels are common between the reach of restoration in

this study and that of Schwartz (2015).

At the former Chambersburg Reservoir Site a forced pool-riffle morphology

was installed in 2013 using a sequence of cross vanes, jack dams, and log deflectors

(bank vanes) to improve the habitat for brook trout in the former reservoir bottom

(Trout Unlimited, 2012). These sorts of structures simulate natural stream

morphologies and provide essential habitat area for fish and their prey. The impacts

of this type of stream restoration (on the restored reach and adjacent, downstream

reach) are investigated in Part 3 of this study.

Hydraulic Modeling Approach: USACE HEC-RAS

The U.S. Army Corps of Engineers Hydraulic Engineering Center – River

Analysis System (HEC-RAS) computer modeling program was chosen to aid in the

completion of this project. HEC-RAS numerically simulates water flowing through a

42

stream channel by simplifying the channel along one dimension and solving the

Energy equation using the standard step method (USACE, 2010). HEC-RAS is

capable of modeling stable and unstable (Davis, 1902), and gradually varied flow in

natural and constructed channels (USACE, 2010).

The Hydraulic Modeling Approach is used commonly to study stream

stability and the maintenance of pool-riffle sequences. Importantly, HEC-RAS

allows for the hydraulics of the channel to be assessed in the case of both natural

streams and stream restorations. The boundary conditions required for input into

HEC-RAS are cross-sectional geometry, water surface elevation (at a stream gage),

Manning’s roughness coefficients, and the expansion/contraction coefficients. (Each

of these technical terms is explained below in Chapter 4: Methods.) Although HEC-

RAS is simple when compared to two- and three-dimensional models, perhaps the

largest benefit of HEC-RAS models is that they may be applied over large spatial

and temporal scales (Harrison and Keller, 2007).

Buchanan (2010) used HEC-RAS to monitor a natural channel design stream

restoration of the Six Mile Creek in Central New York State. The main goal of this

stream restoration project was to protect banks from scouring using a natural

channel design that also restored fish habitats and aided in minimizing the impact of

future flood events (Buchanan et al., 2010). HEC-RAS was used to quantify and

compare post-restoration channel geometries (and associated hydraulic parameters)

for two years after completion of the restoration. In this case, HEC-RAS was able to

43

show areas of stream channel that exceeded common thresholds for stability

following restorations (Buchanan et al., 2010).

HEC-RAS has also been used to model dam removal scenarios. Tullos (2010)

simulated the removal of the Chiloquin Dam removal from the Sprague River in the

Cascade Range of south-central Oregon. This study used HEC-RAS to predict

erosion associated with the dam’s removal, and compared pre- and post-removal

bathymetric and sediment surveys to results produced using HEC-RAS. It was

found that HEC-RAS over-predicted erosion within the former reservoir and

downstream, and that the geomorphic impacts of the dam’s removal were small

even with the estimated 49,000 – 61,000 tons of sediment trapped behind the dam

prior to removal (Tullos et al., 2010).

Summary

In summary, among the issues reviewed as part of this section perhaps most

important are the topics of; shear stress and stream stability, bankfull discharge,

riprap channel armoring, and forced pool-riffle morphology stream restorations.

These four concepts are common throughout the work completed here. The shear

stress at bankfull discharge levels is one of the main focuses of the modeling projects

conducted here, so shear stress, stream stability, and bankfull discharge are all

important concepts.

44

The relevant channel treatments are also important. Riprap channel armoring

and forced pool-riffle morphology stream restorations are two common practices in

the field of stream restoration. Both of these strategies have been used in the case of

the Birch Run dam removal, and their impacts on shear stress, velocity and stream

power are investigated as part of this work.

45

CHAPTER 4: METHODS

Introduction

Here, the methodology for this study will be explained. Topics including; 1)

the two constructed HEC-RAS models, 2) bathymetric cross-section surveying, 3)

floodplain extraction and model construction, 4) flow data estimation methods, and

5) result processing (which includes the answering of the three research questions

mentioned earlier in Chapter 1) will be outlined in this section.

Bathymetric Cross-section Surveying

The cross-sectional data for HEC-RAS model construction was collected in

May and June of 2015 over the course of three weeks of field work. Elevation

surveying was conducted using a TOPCON ES-105 Easy Station, TOPCON FC-500

Field Controller with integrated GPS, adjustable prism pole, and reflective prism.

Surveying was spatially anchored to a permanent benchmark located atop the right

abutment of the former dam and a temporary benchmark established on top of the

left side of the abutment. For benchmark data see APPENDIX B.

To deal with the abundance of vegetation in the study area traverses were

used to span lengths between the cross-sections. Sixty-six stations were needed to

46

span the total distance, and were placed to provide for the best line of site for cross-

section surveying to be conducted over the width of the stream channel. Station

placement was dependent on the maximum distance that could be surveyed while

avoiding vegetation obstructions.

Cross-sections surveyed for the study were positioned to capture the

channel’s natural pool-riffle morphology, as well as the forced pool-riffle restoration

work. The cross-sections positioned to capture the geometry of the cross vanes, bank

vanes, and riprap channel lining were located to effectively capture the complete

geometry of each of the structures. Around structures a higher density per channel

length of cross-sections was necessary to effectively model the structure and its

hydraulic effects. For bathymetric cross-section endpoint data see APPENDIX C.

Floodplain Extraction and Model Construction

Prior to floodplain extraction the bathymetry cross-sections were displayed in

ArcMAP. Floodplain cross-sections were digitized beginning at each of the channel

cross-section endpoints and were extended to their intersection with another cross-

section line, or to the necessary distance to display all modeled floods. In ArcMAP,

the 3D Analyst extension was used to extract elevation profiles for each of the

digitized floodplains. The extracted floodplain profiles were exported to Microsoft

Excel where they were merged with the surveyed bathymetry cross-sections prior to

47

HEC-RAS input. Downstream reach lengths were measured using the measuring

tool in ArcMAP for input into HEC-RAS.

After organizing the appropriate cross-section data, the cross-sections were

entered into the HEC-RAS model one-by-one. Bank stations were designated on

either side of the channel at the apparent top of the stream banks, and Manning’s

Roughness Coefficients that were recorded in the field during surveying were input.

The various Manning’s Roughness Coefficients are organized in Appendix D, as

well as for each of the cross-sections in Appendix E. Expansion and contraction

coefficients were left as the default, 0.3 and 0.1 respectively. These are the typical

expansion and contraction coefficients for gradual, subcritical flow transitions

(USACE, 2010).

Flow Profile Discharge Estimation

Determining flow data for calibration and modeling input was a challenge for

this study. Lack of data was the main limitation, as recurrence interval discharge

rates were impossible to calculate. Instantaneous peak and daily mean discharge

measurements from the USGS were available for the Conococheague Creek gage, so

good estimations and calibration was possible for the upper reach of the

Conococheague Creek. On the other hand, only two questionable depth/discharge

measurements and five discharge field measurements exist in historic records for the

Birch Run Gage. The discharge for the Birch Run upstream boundary condition was

48

averaged from the available data collected since the 1970 installation of the upstream

Long Pine Run Reservoir. The use of these data (and averaging method) likely

represent low flow discharges as the Long Pine Run Reservoir is expected to store a

portion of runoff during precipitation events (even though it is not a flood-control

dam).

To deal with incomplete data, flow data for modeling was estimated as to

cause incipient motion of dominating bedload materials. So, Flow Profiles for this

study (Flow Profiles A – E) were selected following analysis of three years of

Wolman pebble count data. Flow Profile A was selected so fluid shear stresses

produced in modeling reached the critical shear stress level necessary to transport

fine, bedform-controlling sediments (medium gravel). Flow Profile B was selected to

simulate bankfull discharge. Flow Profiles C thru E were selected to simulate

discharge levels at which the dominant bedform-controlling sediments would be in

transport. These flow data were input into modeling as steady state flows.

To determine the dominant bedload sediment size, data from nine sets of

Wolman pebble counts acquired by the Field Techniques Course (GEO 440) in the

Geography and Earth Science Department. Each count collected at least 100 samples

in generally straight segments of channel free of bars/pools/riffles, either within,

upstream, or downstream of the former reservoir site. Here, these results were

averaged to reveal the dominant bedload sediments over the sampling period. The

result of this procedure was a representative bed material size distribution for the

study area that could be used to devise modeling discharges. The modeling

49

discharges produced by this method represent discharges necessary to transport the

dominant material (that is large enough to control bedform) in the stream channels

in and around the study area.

Regarding the portions of this study concerned with bankfull discharge, the

discharge rate associated with the bankfull stage level was estimated using a

manual, iterative procedure which required the researcher to enter a range of

discharge levels, and select the one that was largest in discharge but entirely

contained within the channel banks. Since the reach upstream of the reservoir

(Reach 5) is the only reach not impacted by the dam/reservoir, the discharge level

that best fills the channel of Reach 5 was selected as the bankfull discharge level.

Constructed HEC-RAS Models

Two different HEC-RAS models were necessary to answer the research

question associated with Part 3 of this study, one model with cross-sections

representing the pool-riffle restoration inserted in Reach 4 and one without the pool-

riffle restoration cross-sections inserted. The restoration was represented by a total

of 52 cross-section geometries over the 750 meters (2460 ft.) of Reach 4. The model

without the stream restoration geometry was created by removing the 52 cross-

sections (associated with the pool-riffle structures) and adjusting the downstream

reach lengths in the HEC-RAS cross-section editor. The existence of the pool-riffle

50

stream restoration does not impact stream hydraulics within the riprap-lined reach,

thus either model could have been used in Parts 1 and 2 of the investigation.

Depth/Discharge Model Calibration

To attempt to calibrate the models, two stream locations were included in

modeling. First, a depth/discharge rating curve for the upstream USGS Gage

(01614090) (seen in Figure 11) was produced from instantaneous peak discharge and

depth data available online from the USGS (for instantaneous peak discharge data

see Table 7). The available depth/discharge data was input as a boundary condition

for flow at the upstream cross-section on the Conococheague Creek (cross-section

175), and as a rating curve at the same cross-section (with lack of downstream

boundary data, the downstream boundary conditions were set to a normal water

depth with a slope of 0.002).

Due to data limitations, the same procedure could not be conducted for the

USGS Birch Run gage (01614100) (also seen in Figure 11) so the five discharge

measurements collected since the installation of the upstream Long Pine Run

Reservoir in 1970,were averaged and held constant through modeling of each Flow

Profile. This limitation does not impact the modeling results in the study reach

because the gage is a sufficient distance upstream from the study area.

51

Figure 11: Field photo of the two former USGS gage locations used for model calibration and flow data estimation. Left image is of the Birch Run gage, for which extreme data limitations existed. Right image is of the Conococheague Creek gage, for which instantaneous annual peak discharge and daily mean discharge data were available. Data limitations regarding the Birch Run gage meant that calibration was impossible. The study area is far enough from each of the stream gages that the calibration of them is not essential. The Birch Run gage (01614100) is seen at left, and the Conococheague gage (01614090) is seen at right. Flow direction is indicated by the white arrow. (Photos from May 2015)

To assess model performance, the residual error for each of the modeled

discharges was calculated by subtracting each resultant modeled depth at the stream

gage from the depth estimated from a trendline that statistically fits the gage data

(with an R2 > 0.95) . The resultant residual error for each modeled flow profile

indicates the error (in meters) in modeled depth produced by a modeled discharge,

in relation to the real-life data collected by the gage.

Sediment Transport Capability Assessment

The methodology of this portion of the study summarizes, reach by reach, the

maximum sediment size that is capable of being transported by each of the

52

simulated flow profiles. This section applies the concepts of fluid and critical shear

stress to determine (according to work by Berenbreck and Tranmer, 2008) if

sediments of given sizes (that are common in the stream channel near/within the

study area) are capable of being transported at the modeled flow profiles (Flow

Profiles A – E).

Results for fluid shear stress for each reach are averaged from cross-sections

within each reach (Reaches 1 – 5) and then compared to estimates for critical shear

stresses of natural sediment mixtures from Berenbreck and Tranmer (2008). Each

flow profile is summarized, and significant hydraulic parameters – such as

hydraulic radius and slope – are noted. For each reach, if the level of average fluid

shear stress exceeds the level of critical shear stress required to initiate motion of the

given sediment size class, that given sediment class will be in active transport within

that reach.

Result Processing

Reflecting back to Chapter 1, three research questions were to be answered

through this research. These three questions required numerical comparisons of

various hydraulic parameters. They regarded comparisons of; 1) hydraulic

parameters (shear stress, stream power, flow velocity, hydraulic radius, flow area,

and energy gradient slope) between the riprap lined reach (Reach 2) and the

53

adjacent reaches (Reaches 1 & 3), 2) flood channeling within the riprap lined reach

(Reach 4) and adjacent reaches (Reaches 1 & 3), and 3) pre/post restoration levels of

hydraulic parameters such as energy gradient, flow velocity, shear stress, and

stream power within and downstream of the pool-riffle morphology restoration in

Reach 4.

Pt. 1: Investigating the Bankfull Shear Stress within and adjacent to the Riprap-

lined Reach

Part 1 of this study compares levels of shear stress, flow velocity, hydraulic

radius, flow area, and energy gradient of the bankfull discharge between the riprap-

lined reach (Reach 2) and the adjacent reaches (Reaches 1 and 3). Numerical HEC-

RAS modeling results were exported to Microsoft Excel where the results were

averaged, compared, and visualized. For detailed views of cross-sections refer to

the “Sediment Transport Capability” section in Chapter 5.

To determine changes in flow behavior throughout the riprap-lined reach,

hydraulic attributes were subtracted between adjacent cross-sections used for this

comparison. Flow velocity, shear stress, stream power, slope, and hydraulic radii

were subtracted between each of the cross-sections as to sense how flow changes as

it enters and exits the riprap lined reach. To do so the following calculation,

proceeding in the direction of flow, was conducted for each cross-section within the

selected stream reaches:

54

V (upstream section) – V (adjacent downstream section) = Δ V (m/s), (Eq. 2)

where V is velocity. This calculation allows for a simplified look into how flow changes

between reaches, where morphological differences may exist and cause some sort of

hydraulic response

Similarly, the same method was also applied to the shear stress of the channel to

detect areas of channel where frictional force is either gained or lost. The change in

shear stress between each of the cross-sections, proceeding in the direction of flow, was

calculated as:

τ (upstream section) – τ (adjacent downstream section) = Δ τ (N/m2) (Eq. 3)

where τ is shear stress. Changes in shear stress are resultant of where the channel

changes shape or slope, and the frictional force of flow either declines (in the case of a

transition into a wide or gradually sloping stream) or increases (in the case of a

transition into a narrow or steep stream reach). Thusly, the concepts applied in these

methods are also applied to the stream power, channel slope, and hydraulic radius so

changes in hydraulic parameters such as shear stress may be further investigated

between adjacent cross-sections.

55

Pt. 2: Flood Channelization Comparison for the Riprap-lined and Adjacent Reaches

This part of the study focused on the ability of the riprap-lined channel

segment to channelize discharges at the 2-, 5-, 10-, and 20-year recurrence intervals.

To determine the channelization at each cross-section within a reach the channel

width was divided by the top width of the water surface. A ratio greater than one

signifies the width of the water surface being greater than that of the channel width,

and means that flooding exists within that cross-section. Channelization, flow that is

completely contained within the stream’s banks, is signified by a ratio of one. So a

value higher than one means there is flooding, and a value of one means that the

discharge is channelized. This can be represented mathematically by:

𝐹𝑙𝑜𝑤 𝑇𝑜𝑝 𝑊𝑖𝑑𝑡ℎ

𝐶ℎ𝑎𝑛𝑛𝑒𝑙 𝑇𝑜𝑝 𝑊𝑖𝑑𝑡ℎ= 𝐹𝑙𝑜𝑜𝑑 𝐸𝑥𝑡𝑒𝑛𝑡 (𝑜𝑟 "𝐶ℎ𝑎𝑛𝑛𝑒𝑙𝑖𝑧𝑎𝑡𝑖𝑜𝑛") (Eq. 4)

For this relationship, a “channelization” greater than one would represent

flooding in width of channels. Any “channelization” value of one signifies that the

modeled discharge is contained completely within the bank stations designated in

modeling. For example, a channelization value of 1.5 represents a cross-section at

which there is flooding with a total top-width that is 1.5 times the width of the

channel.

The “channelization” value cannot be less than one because when discharges

are completely channeled HEC-RAS reports the flow top width and channel top

56

width as the same value. This results in a minimum value of one when calculating

the channelization using these methods, which does not impact the answering of the

fore-mentioned research questions.

Pt. 3: Investigating the Hydraulic Effects of a Pool-Riffle Morphology Stream

Restoration on Bankfull Velocity, Shear Stress, and Stream Power

Part three of this study tests the pool-riffle morphology stream restoration’s

impact on the reach of installation and the adjacent, downstream reach. Results in

Reach 4 (and just downstream of Reach 4 at cross-section 82) from pre- and post-

restoration HEC-RAS models were averaged between scenarios and compared

within Microsoft Excel. Changes in the minimums and maximums of stream flow

velocity and shear stress were calculated for the restored reach. Additionally,

changes in the number flow transitions, peaks, and troughs for each of the hydraulic

parameter profiles were recorded (this term is being called peak density here).

To test for any downstream impact, results for the first cross-section

immediately downstream of the restoration, cross-section 82, were compared

between pre- and post-restoration scenarios to detect any changes. Results produced

here investigate any possible, abnormal downstream impacts that would fall outside

of the local changes in flow behavior that are normally observed in the case of forced

pool-riffle morphology stream restorations.

57

CHAPTER 5: RESULTS

Introduction

This section presents results of; 1) the flow data estimation method, 2) model

calibration, 3) the sediment transport capability study, and 4) Parts 1 thru 3

answering the research questions presented above in Chapter 1. Methods applied in

production of these results are presented above in Chapter 4.

Flow Data Estimation Method

To model a set of discharges that would produce fluid shear stress levels

necessary to carry the dominant bedload sediments at the former Chambersburg

Reservoir site, Wolman pebble count data from past Geography Field Techniques

courses (years 2009, 2011, and 2013), who use the former Chambersburg Reservoir

study area as a classroom, were averaged (see Figure 12 and Table 2 below).

Detailed Wolman pebble count data is located in APPENDIX H.

Sediment classes that were most abundant during pebble count sampling

were fine cobbles, sand, very coarse gravel, and coarse gravel. Of the bed-shape

controlling materials; fine cobbles ranked highest in occurrence (20%), sand next

(14%), then very coarse gravel (12%), and coarse gravel (10%).

58

Figure 12: Average Bedload Class Distribution for the former Chambersburg Reservoir study area. Samples were collected in 2009, 2011, and in 2013 by the Shippensburg University Geography 440: Field Techniques course. Sampling locations were; 1 in Reach 3, 1 in Reach 4, 1 upstream of USGS Gage 01614090, 1 upstream of USGS Gage 01614100, and 1 downstream of Reach 1. Averaged samples show a bed material that is dominated by fine cobbles, at over 20% occurrence in sampling. Data is presented in Table 2, and APPENDIX H.

0 5 10 15 20 25

Sands

Very Fine Gravel

Fine Gravel

Medium Gravel

Coarse Gravel

V. Coarse Gravel

Fine Cobble

Coarse Cobble

V. Coarse Cobble

Small Boulder

Medium Boulder

Large Boulder

V. Large Boulder

Percent of Total (all samples 2009 - 2013)

Bed Material Size Distribution for the Former Chambersburg Reservoir Dam Removal Site

(2009 -2013)

59

Table 2: Summary of bed material size distribution data from Figure X. Bed material samples collected were averaged across the study area to obtain a general estimate of the dominant bedload materials. From sampling, fine cobbles dominate the composition of the bed, along with sand, very coarse gravel, coarse gravel, and coarse cobbles. The results from these data were applied to estimate discharge levels that would initiate transport of these bed materials.

Class Size (mm) Percent of

Total Cumulative Percentage

Sands < 2 14.28 14.28

Very Fine Gravel 2-4 0.72 15.00

Fine Gravel 4-8 3.55 18.55

Medium Gravel 8-16 6.34 24.89

Coarse Gravel 16-32 10.26 35.15

V. Coarse Gravel 32-64 12.62 47.77

Fine Cobble 64-128 20.66 68.43

Coarse Cobble 128-180 9.63 78.06

V. Coarse Cobble 180-256 8.49 86.55

Small Boulder 256-572 9.02 95.57

Medium Boulder 572-1024 3.15 98.72

Large Boulder 1024-2048 1.27 99.99

V. Large Boulder 2048-4096 0.00 99.99

Based on the analysis of Wolman pebble counts from 2009, 2011, and 2013,

the predominating bed materials by frequency (not volume) are fine cobbles, sand,

very coarse gravel, and coarse gravel. The sand, which totaled 14% of bed material

that was sampled will fill in areas among the larger sediments, and settle in pools

protected from scouring during flood discharges. Discharge events that generate

enough fluid shear stress to mobilize the more abundant material (the fine cobbles,

very coarse gravel, and coarse gravel, which makes up 43% of the total sampled

bedload material) will have the greatest control on bedform within the study area.

So, with interest in bankfull flow and bedform-controlling discharges, the

discharge estimates were selected so the fluid shear stress produced in modeling

was greater than that of the dominating sediments within the channel. Of these

60

discharges, Flow Profile A was modeled to simulate transport of smaller bed

material (Med. Gravel). Flow Profile B was selected as the bankfull discharge.

Profiles C – E, were selected so that fluid shear stresses produced in modeling were

capable of transporting the sediments dominating the Wolman pebble count data

(fine cobbles). The selected discharge levels for Flow Profiles A – E are presented in

Table 3.

Table 3: Summary table of selected flow data for modeling. Discharge values were selected so fluid shear stress levels produced were great enough to initiate motion of bed-sample-dominating sediments. Flow Profile A (FP A) was selected to simulate transport of fine bed-material sediments, FP B was selected to simulate bankfull discharge, and FP’s C thru E were selected to initiate motion of the largest, most abundant sediments. Lack of data from the Birch Run gage led to the averaging of the available data and the discharge being held constant due to the presence of the upstream Birch Run Reservoir.

Discharge, cms (cfs)

Flow Profile

Conococheague Creek (01614090)

Birch Run (01614100)

Sum at Confluence

A 0.6 (20.8) 0.09 (3.3) 0.7 (24.1)

B 2.9 (103.5) 0.09 (3.3) 3.0 (106.8)

C 5.8 (204.8) 0.09 (3.3) 5.9 (208.1)

D 8.6 (303.7) 0.09 (3.3) 8.7 (307)

E 9.8 (346.1) 0.09 (3.3) 9.9 (349.4)

From the analysis of available Wolman pebble count data (and determination

that bed-samples were dominated by fine cobbles, very coarse gravel, coarse gravel,

and medium gravel), discharge levels for the simulated Flow Profiles were selected

to exceed the transport threshold of these sediments (presented in Table 3).

Again, bankfull discharge (3.02 cms, or 106.8 cfs) was selected because this is

the level of discharge that fills banks in Reach 5 (the most natural of the surveyed

61

stream reaches) without causing any flooding. All other reaches were either

inundated by the reservoir (Reaches 3 and 4), were restored (Reach 2), or

downstream of the former dam (Reach 5).

Model Calibration Results: Assessing Model Accuracy

With the data that was available, flow calibration and the assessment of

modeling accuracy within each of the reaches in the study area was not possible.

Because the only available depth/discharge data was collected from the upstream

USGS gage on the Conococheague Creek this was the only cross-section of stream

that can be accurately calibrated.

After initial modeling, and entering depth/discharge rating curves (for the

cross-section representing the Conococheague Creek stream gage) in HEC-RAS the

accuracy of modeling was determined by relating the results of the modeled Flow

Profiles to the logarithmic trendline that fits the instantaneous peak data

(depth/discharge) data with an R2 value of 0.99. Residual depth errors for each of

the modeled Flow Profiles were also calculated to determine the error in the

simulated depths produced by the input modeling discharges.

Figure 13 presents the depth/discharge relationship for the USGS stream

gage on the Conococheague Creek and depth/discharge relationship for the

modeled Flow Profiles. Trendlines for each set of data (gage data and simulated

62

data), and their equations and R2 values are presented. The trendline for the

Conococheague Creek gage data fits its’ respective data with an R2 value of 0.99.

Both the trendline for the gage data and that of the Flow Profile simulation are very

similar. The trendline for the simulated Flow Profiles fits its’ data with an R2 of 0.97,

and both equations have slopes of 0.17ln(x) (and only vary at the thousandths place).

Figure 13: Depth/Discharge curve for the Conococheague Stream gage (UGSG gage 01614090) and modeling results for each of the Flow Profiles (A – E). Conococheague Creek instantaneous peak depth/discharge gage data (blue diamonds) and depth/discharge relations from modeled flow profiles (red squares), and their trendlines are presented. Both trendlines were successful in representing their data (when evaluated at a 5% error level), and have slopes equal to 0.17ln(x). Residual errors for modeling results were attained by subtracting actual values from the values estimated using the gage data trendline. Overall, modeling was accurate to an average of 2.6 centimeters at the calibrated stream cross-section.

63

Residual depth errors (in units of depth) were calculated for each of the

modeled discharges. These results are presented in Table 4. Modeled discharges,

modeled depths, estimated depths and the residual error in each modeled depth are

presented. Depth errors were determined by subtracting the modeled depth value

from the depth predicted at the Conococheague Creek USGS gage. The resultant

average error of the five Flow Profiles (Flow Profiles A – E) was 0.026 m (0.08 ft.), or

2.6 centimeters (1.02 in.). With the average error being less than 3% of the average

depth, and model calibration not impacting the study reaches, no further calibration

was necessary.

Table 4: Results of the model calibration and error determination, for which the residual error (in depth units) for each of the modeled discharges was calculated. Modeled discharge levels and their associated depths were compared to depths estimated from a trendline statistically associated with the instantaneous peak depth/discharge data from the Conococheague Creek USGS gage. Residual depth errors were calculated for each discharge. The average modeling error was 0.026 meters for all of the modeled Flow Profiles, which amounts to less than 3% error in depth calculations.

Flow Profile

Errors between modeled and gage-recorded depths

Modeled Discharge

Modeled Depth

Estimated Depth

Residual Error

cms (cfs) m (ft) m (ft) m (ft)

A 0.69 (24.1) 0.52 (1.7) 0.55 (1.8) -0.03 (-0.09)

B 3.02 (106) 0.88 (2.9) 0.83 (2.7) 0.05 (0.16)

C 5.89 (208) 0.96 (3.1) 0.98 (3.2) 0.02 (0.07)

D 8.69 (307 1 (3.3) 1.01 (3.3) -0.01 (-0.03)

E 9.89 (349) 1.01 (3.6) 1.03 (3.4) -0.02 (-0.07)

Overall, modeled Flow Profile scenarios predicted recorded depths that very

closely imitated the available instantaneous peak, depth/discharge data. An error of

less than 3% of the average channel depth is acceptable and should result in no

64

major errors when estimating hydraulic parameters such as shear stress or stream

power.


This portion of the study averaged shear stress values for each reach, at each

of the modeled discharge levels, and determined the maximum median sediment

size (d50 from Equation 1, pg. 32) capable of being transported throughout the study

area. Here, results are presented for each Flow Profile (A – E) with the maximum d50

sediment size capable of being transported at that discharge for each of the five

divided reaches labeled in Figure 2 (for information regarding each reach refer to

CHAPTER 2: Study Area).

Results are presented in Figures 14 thru 18, and do not only present the

results of the sediment transport capability assessment but also reveal important

knowledge pertaining to the science and strategy of dam removal (i.e. general

discharge level at which dam abutments, spoil, wetland, or silt cap are inundated).

Perhaps most significantly, erosional and depositional trends can be determined for

each of the study reaches. At the end of this section, a summary figure (Figure 19)

presents sediment size transport capability results for all of the modeled reaches and

discharges.

65

Flow Profile A

Flow Profile A simulated a discharge of 0.69 cms (24.1 cfs). Flow was

completely channeled throughout the entire study area (Reaches 1 – 5), and

upstream. So, this discharge level presents no threat to the spoil, remaining dam

abutments, or silt cap. A map displaying the extent of the water surface at each

cross-section, and the maximum size of sediment that each reach is (on average) able

to transport during an event of the modeled discharge, is presented in Figure 14. In

Figure 14 it is clearly observable that Reaches 1, 3, 4, and 5 are capable of

transporting coarse gravels, and that Reach 2 is capable of transporting medium

gravel.

66

Figure 14: Sediment Transport Capability Assessment results for Flow Profile A within the Chambersburg Reservoir study area. Cross-sections are green lines, water surface extent is seen as blue, reach divisions are white, and each cross-section is numbered. Each reach is labeled, along with the maximum sediment size (signified by the shape below each reach label) that can be transported (on average) within each reach. These results show that Reaches 1, 3, 4, and 5 are all capable of transporting very coarse gravels, but the riprap-lined reach, Reach 2, is only capable of transporting medium gravel. Variables that influence shear stress, and a summary of flow velocity and maximum sediment size, are presented in a table at the bottom of the figure.

From the sediment transport capability results for Flow Profile A (presented

in Figure 14), because sediment sizes being transported are the same (coarse gravel)

as flow proceeds from Reach 5 thru Reach 3 sediment transport will be at a general

67

(reach-averaged) equilibrium. Between Reach 3 and Reach 2, because larger

sediments (coarse gravel) are transportable within Reach 3 (medium gravel), there

will likely be net deposition (of coarse gravel-dominated sediment) within Reach 2.

Between Reach 2 and Reach 1, because there is an increase in the maximum size of

sediment capable of being transported, erosional scouring of coarse gravel-sized

material (but not larger) will likely take place in Reach 1.

Flow Profile B

Flow Profile B simulated bankfull discharge, which was determined to be

about 3.02 cms (106 cfs). This level of discharge fills the channel (to the top of the

banks) in Reach 5 (which is the one reach of channel not impacted by the former

reservoir or -footprint) without causing any flooding. Flooding exists in Reach 4 at

cross-section 121 - 122, and in Reach 1 at all cross-sections (see Figure 15). The

flooding that is produced does not encroach upon the silt cap, spoil pile, or

remaining dam abutments.

A map displaying the extent of the water surface at each cross-section, and

the maximum size of sediment that each reach is (on average) able to transport

during an event of the modeled discharge, is presented in Figure 15. In Figure 15 it is

clearly observable that Reaches 1 and 2 are only capable of transporting coarse

gravels, while Reaches 3, 4, and 5 are capable of transporting very coarse gravels.

68

Figure 15: Sediment Transport Capability Assessment results for Flow Profile B within the Chambersburg Reservoir study area. Cross-sections are green lines, water surface extent is seen as blue, reach divisions are white, and each cross-section is numbered. Each reach is labeled, along with the maximum sediment size (signified by the shape below each reach label) that can be transported (on average) within each reach. These results show that Reaches 1 and 2 are capable of transporting coarse gravel, and that reaches 3, 4, and 5 are all capable of transporting very coarse gravel. Variables that influence shear stress, and a summary of flow velocity and maximum sediment size, are presented in the table at the bottom of the figure.

Results for maximum transportable sediment size at the discharge of 3.02 cms

(106.8 cfs) for Flow Profile B again determines general erosional and depositional

patterns between the study reaches. At this discharge rate, Reaches 5, 4, and 3 are

69

capable of transporting very coarse gravels, which means that these reaches will be

at a general (reach-averaged) equilibrium in terms of sediment transport size.

Between Reach 3 and Reach 2, because Reach 3 is capable of transporting very

coarse gravel and Reach 2 is only capable of transporting coarse gravel, sediments

that are very coarse gravel-sized will be deposited within Reach 2 (possibly causing

sorting). Reach 2 and Reach 1 are each able to transport coarse gravel so these

reaches may be at a general sediment transport equilibrium during bankfull

discharge events.

Flow Profile C

Flow Profile C simulated a discharge of 5.96 cms (210.5 cfs). This level of

discharge produces the first instance of flooding in Reach 5. Flooding in Reach 4

exists at cross-section 121 - 122, and 110. In Reach 3, sections 78, 42 – 43, and 40 are

flooded. Downstream in Reach 1, all cross-sections are flooded (see Figure 16). The

flooding that is produced does inundate areas of the former silt cap, and reaches the

base of the spoil pile (cross-sections 56 – 57). Flow is channeled in the vicinity of the

remaining dam infrastructure (Reach 2).



during an event of the modeled discharge, is presented in Figure 16. In Figure 16 it

70

can be seen that Reach 2 is only capable of transporting coarse gravel, while Reaches

1, 3, 4, and 5 are capable of transporting very coarse gravels.

Figure 16: Sediment Transport Capability Assessment results for Flow Profile C within the Chambersburg Reservoir study area. Cross-sections are green lines, water surface extent is seen as blue, reach divisions are white, and each cross-section is numbered. Each reach is labeled, along with the maximum sediment size (signified by the shape below each reach label) that can be transported (on average) within each reach. These results show that Reach 2 is capable of transporting coarse gravel, and that reaches 1, 3, 4, and 5 are all capable of transporting very coarse gravel. Variables that influence shear stress, and a summary of flow velocity and maximum sediment size, are presented in the table at the bottom of the figure.

71

At 5.89 cms (208.1 cfs), because fluid shear stress levels causes incipient

motion of very coarse gravel in Reaches 5, 4, and 3, it is likely that these reaches of

stream will be at a general equilibrium at this discharge rate. Because Reach 2

transports finer bed material (coarse gravel) than Reach 3 (very coarse gravel) there

is likely to be net deposition within Reach 2 (of mainly very coarse gravels. Finally,

with Reach 1 transporting larger bed material than Reach 2 (very coarse gravel

compared to coarse gravel) Reach 1 will undergo net erosion (sediment loss) at the

Flow Profile C discharge.

Flow Profile D

Flow Profile D simulated a discharge of 8.69 cms (306.8 cfs). Results are seen

in Figure 17. This level of discharge produces only a small area of flooding in Reach

5. Flooding in Reach 4 exists at cross-sections 121 - 122, 117, 110, and 85 - 83. In

Reach 3, areas around cross-sections 78, 67 – 68, 57 – 56, 42 – 43, and 40 - 39 are

flooded. Downstream in Reach 1, all cross-sections are flooded. The flooding that is

produced does inundate areas of the former silt cap, and reaches the base of the

spoil pile (cross-sections 56 – 57). Flow is channeled in the vicinity of the remaining

dam infrastructure.

72




can be seen that Reaches 2 and 3 are capable of transporting very coarse gravel,

while Reaches 1, 4, and 5 are capable of transporting fine cobbles.

73

Figure 17: Sediment Transport Capability Assessment results for Flow Profile D within the Chambersburg Reservoir study area. Cross-sections are green lines, water surface extent is seen as blue, reach divisions are white, and each cross-section is numbered. Each reach is labeled, along with the maximum sediment size (signified by the shape below each reach label) that can be transported (on average) within each reach. These results show that Reaches 2 and 3 are capable of transporting very coarse gravel, and that reaches 1, 4, and 5 are capable of transporting fine cobbles. Variables that influence shear stress, and a summary of flow velocity and maximum sediment size, are presented in the table at the bottom of the figure.

Regarding erosional and depositional trends at the discharge of Flow Profile

D (8.69 cms, or 307 cfs), with Reach 5 capable of transporting fine cobbles and Reach

4 only capable of transporting very coarse gravel there will likely be net deposition

74

in Reach 4. With the construction of cross-vanes in Reach 4 net deposition within

this reach may cause fine cobble deposition upstream of vanes, or may cause the

constructed pools to be filled with fine cobbles. At this discharge rate, between

Reaches 4, 3, and 2, sediment transport will be at a general equilibrium because the

three reaches are capable of transporting the same-sized materials (very coarse

gravels). Within Reach 1, net erosion is again observed in modeling results becuase

the upstream Reach 2 is capable of transporting smaller sediment than Reach 1 (very

coarse gravel compared to fine cobbles) so scouring of fine cobble-sized sediments

may occur within Reach 1.

Flow Profile E

Flow Profile E simulated a discharge of 9.89 cms (349.4 cfs). Results are

presented in Figure 19. This level of discharge produces again only a small area of

flooding in Reach 5 (cross-sections 163 – 164). Flooding in Reach 4 exists at cross-

sections 121 - 122, 117, 110, and 85 - 83. In Reach 3, areas around cross-sections 78 -

79, 68 – 67, 57 – 56, 42 – 43, and 40 - 39 are flooded. Downstream in Reach 1, all

cross-sections are flooded. The flooding that is produced does inundate areas of the

former silt cap, and reaches the base of the spoil pile (cross-sections 56 – 57). Flow is

channeled in the vicinity of the remaining dam infrastructure (Reach 2).

75




can also be seen that Reaches 2, 3, and 4 are capable of transporting very coarse

gravel, while Reaches 1, and 5 are capable of transporting fine cobbles.

76

Figure 18: Sediment Transport Capability Assessment results for Flow Profile E within the Chambersburg Reservoir study area. Cross-sections are green lines, water surface extent is seen as blue, reach divisions are white, and each cross-section is numbered. Each reach is labeled, along with the maximum sediment size (signified by the shape below each reach label) that can be transported (on average) within each reach. These results show that Reaches 2, 3, and 4 are capable of transporting very coarse gravel, and that reaches 1 and 5 are capable of transporting fine cobbles. Variables that influence shear stress, and a summary of flow velocity and maximum sediment size, are presented in the table at the bottom of the figure.

Erosional and depositional trends at the discharge of Flow Profile E (9.89 cms,

or 307 cfs) are the same as Flow Profile D. Scouring of fine cobbles in Reach 5, and

their transport downstream may cause deposition of fine cobbles within Reach 4,

77

threatening the long-term performance of the installed pool-riffle restoration. With

deposition occurring in Reach 4, and Reaches 3 and 2, each being able to transport

very coarse gravel these reaches will likely be at a general equilibrium. Within Reach

1, net erosion is again observed in modeling results because the upstream Reach 2

transports smaller sediments than Reach 1 (very coarse gravel compared to fine

cobbles) so scouring (causing net erosion) of fine cobble-sized sediments may occur

within Reach 1.

Summary

Modeling results showed that, relatively speaking, Reaches 5 and 1 typically

produce the greatest levels of shear stress and transport the largest sediment classes

(for each of the modeled discharges) when comparing reaches across the study area.

Flooding was persistent in Reach 1 (the reach downstream of the former dam) at all

modeled discharges greater than Flow Profile A (0.69 cms, or 24.1 cfs). Flooding

reached the base of the spoil pile at the discharge of 5.9 cms (208.1 cfs) (Flow Profile

C). Within the riprap channel-lining (Reach 2), all modeled Flow Profiles appear to

be channeled.

In terms of sediment transport size, a summary graph is presented in Figure

19. The graph displays the critical shear stress levels for each of the sediments that

dominate the bed material composition (seen as blue lines), and the resultant

78

average fluid shear stress (presented as each of the points). Reaches 1 thru 5 are each

represented by green squares, grey circles, yellow triangles, red diamonds, and

orange triangles, respectively,

Figure 19: Summary graph of the sediment transport capability study, which determined the maximum size of dominant sediment for each reach in the study area (Reaches 1 – 5). Blue lines indicate critical shear stress levels of the most common bed sediment sizes (determined from Wolman pebble counts) and each of the points represent average fluid shear stresses produced within in each reach at each of the modeled discharges. Reach 1 is represented by green squares, Reach 2 by grey circles, Reach 3 by yellow triangles, Reach 4 by red diamonds, and Reach 5 by orange triangles. Flow Profiles are labeled on the x-axis and shear stress levels on the y-axis. The most commonly witnessed sediment size during pebble counting (fine cobbles) were not transportable until the discharge of Flow Profile C.

79

Figure 19 shows that; 1) Reach 1 displays the greatest range of fluid shear

stresses throughout modeling (thru Flow Profiles A – E), 2) Reach 2 (the riprap-lined

reach) produces the lowest average modeled shear stress levels for each modeled

scenario, 3) Reach 3 and 5 are the most similar of all the modeled reaches, and 4) the

bed material occurred most frequently in Wolman pebble counts from the site (fine

cobbles) weren’t able to be transported until the discharge level associated with

Flow Profile C (5.9 cms, or 208.1 cfs).

From the results in this section and summary graph in Figure 19, it is

observable that Reach 1 underwent net erosion at four of the five modeled discharge

levels. This reach is, based on the modeled discharges and sediment transport

results, most susceptible to net erosion out of the five study reaches. Reach 2

typically produces the lowest levels of shear stress across the study area, pointing to

net sediment deposition within this reach. Reaches 3 and 4 have similar sediment

size transport capabilities and will likely remain at a general equilibrium in relation

to one another. Upstream, Reach 5 underwent net erosion only at discharge rates

associated with Flow Profiles D and E. The erosion of fine cobbles within Reach 5

during these discharge rates, along with lower sediment transport capabilities in

Reach 4, may cause deposition of fine cobbles within Reach 4 and could jeopardize

the long-term success of the stream restoration.

80

Pt. 1: Investigation of Bankfull Shear Stress within and adjacent to the Riprap-

lined Reach

This part of the study compared the average shear stress, stream power,

hydraulic radius, energy gradient slope, flow area, and velocity between the riprap-

lined reach (Reach 2), Reach 1 (the reach downstream) and the portion of Reach 3

that extends upstream from the top of Reach 2 to the next upstream grade

controlling riffle (at cross-section 45). This section also observes changes of flow

velocity, shear stress, and stream power from one cross-section to the adjacent,

downstream cross-section as flow proceeds through the riprap lined reach.

Averages for shear stress, stream power, hydraulic radius, energy gradient,

flow area, and velocity for the reach upstream from the riprap, the riprap-lined

reach, and the downstream reach are presented in Figure 20 below (with summary

data and standard unit equivalents in Table 5). The results show the general shape

of the channel, its slope, and the resultant shear stresses and stream power at the

modeled bankfull discharge.

81

Figure 20: Results of Part 1 for the research question regarding bankfull hydraulics of the riprap-lined and adjacent reaches. Each reach is divided by white lines and labeled, as is the presence of riprap-lining. Reach 3, for this portion of study, was shortened to the next upstream riffle so in this part of the study Reach 3 is comprised of cross-sections 37 – 45. The riprap-lined reach (Reach 2) displays the lowest slope, shear stress, and stream power when compared to Reaches 1 and 3. In Reach 2, at bankfull discharge the hydraulic radius is greatest of the compared reaches.

Table 5: Summary of data seen in Figure 21, from Part 1 analyzing hydraulic characters of the riprap-lined and adjacent reaches. Reach 3 is the reach just upstream of the riprap (cross-sections 37-45), Reach 2 is the riprap-lined reach (36 -28), and Reach 1 is the reach downstream of the riprap (cross-sections 27-22). The riprap-lined reach is shown to display the lowest slope, shear stress, and stream power in comparison to Reaches 1 and 3.

Averages

Units Reach 3

Reach 2 (Riprap)

Reach 1

Shear Stress N/m2 (lb/ft2) 29.09 (0.61) 16.81 (0.35) 25.51 (0.53) Stream Power N/m s (lb ft/s) 39.50 (29.1) 24.08 (17.7) 37.33 (27.5)

Hydraulic Radius m (ft) 0.42 (1.37) 0.46 (1.51) 0.35 (1.14)

E.G. Slope m/km (ft/mi) 10 (52) 5 (26) 7 (36) Flow Area m2 (ft2) 3.45 (37.1) 4.86 (52.3) 7.38 (79.4) Velocity m/s (ft/s) 1.03 (3.37) 0.92 (3.01) 0.92 (3.01)

82

As seen in Figure 20 and Table 5, amongst the reaches compared in this part

of the study Reach 2 has the lowest energy gradient slope of 5 m/km (26 ft./mile),

the largest hydraulic radius of 0.46 m (1.51 ft.), the lowest shear stress 16.81 N/m2

(0.35 lb./sq. ft.), and the lowest stream power of 24.08 N/m s (17.7 lb. ft./s). With a

flow area of 4.86 square meters (52.3 ft2) Reach 2 has a larger flow area than the

portion of Reach 3 at 3.45 m2 (37.1 ft2) and less than Reach 1at 7.38 m2 (79.4 ft2). At

bankfull levels the average velocity of Reach 2 is 0.92 meters per second (3.01 ft./s),

same as that of Reach 1 but less than Reach 3 at 1.03 m/s (3.37 ft./s).

So, Reach 3 (cross-sections 37 – 45) has a smaller flow area, and there is a

greater energy gradient slope when compared to Reach 2 and Reach 1. The riprap-

lined reach (Reach 2) has the lowest energy gradient slope, and a moderate flow area

in comparison to the other reaches. The downstream reach (Reach 1) has the greatest

flow area (because the bankfull discharge causes minor flooding), and an energy

gradient slope just higher than the riprap-lined reach.

Focusing closer on the transitions between each of the cross-sections

modeling the riprap-lined reach and the boundaries between it and the adjacent

reaches the changes in flow velocity, shear stress and stream power between cross-

sections were quantified. This assessment included two cross-sections upstream of

the riprap (cross-sections 38 & 37 in Reach 3), the riprap-lined reach (Reach 2) (cross-

sections 36-28), and two cross-sections downstream of the riprap in Reach 1 (cross-

sections 27 & 26). The results of this portion of the assessment are seen in Table 9

83

where green cells represent a positive change between a cross-section and the

upstream cross-section, red represents a negative change, and yellow signifies no

change.

At the upstream extent of the riprap between cross-sections 37 and 36, a drop

in shear stress, velocity, and stream power are seen. This likely is due to a

broadening of the channel and a decrease of channel slope. Within the riprap-lined

reach there is no consistent trend in the shear stress, velocity, and stream power

values, but levels show a net decrease through the reach. Transitioning to Reach 1

downstream, again seen in Table 6, there is a very slight increase in shear stress,

flow velocity, and stream power between cross-sections 28 and 27 (the transition

from the riprap-lined reach to the unlined, downstream reach). But, the largest

transition is seen just downstream of the riprap, between cross-sections 27 and 26.

Here, shear stress, flow velocity, stream power and channel slope increase, while the

hydraulic radius decreases.

84

Table 6: Results of the detailed cross-section to cross-section analysis for the riprap-lined reach (Reach 1), and the transitions between reaches (from Reach 3 to 2, and from Reach 2 to 1). The table displays changes in flow attributes (shear stress, flow velocity, and stream power) between individual cross-sections in the vicinity of the riprap-lined reach. Green signifies a positive change, red represents negative change, and yellow means no change between a given cross-section and the adjacent, upstream cross-section (above it in the table). Generally, shear stress, flow velocity, and stream power vary agreeably with slope. When hydraulic radius gets smaller, shear stress, flow velocity, and stream power tend to increase. Shear stress decreases sharply as flow enters the riprap-lined reach (Reach 2), where the channel decreases in slope but increases in hydraulic radius. At the downstream end of the riprap, between cross-section 27 and 26 there is a local change in slope that causes flow to accelerate and shear stress/stream power to increase

Flow Character and Channel Shape Changes in Vicinity of the Riprap-lined Reach

Reach

Segment

Cross-

section

Δ Shear

Stress

Δ Flow

Velocity

Δ Stream

Power Δ in

Slope

Δ in

Hydraulic

Radius

N/m2

(lb/ft2) m/s (ft/s)

N/m s

(lb ft/s)

m/km

(ft/mi) m (ft)

Reach 3 38 57.11 (1.19) 1.1 (3.61) 94.7 (69.8) 23 (121) -0.46 (-1.5)

Reach 3 37 2.5 (0.05) 0 (0) 4.0 (2.9) 4 (21) -0.02 (0.06)

Reach 2 36 -49.41 (-1.03) -0.56 (-1.83) -86.2 (-63.6) -24 (-126) 0.23 (0.75)

Reach 2 35 34.54 (0.72) 0.69 (2.26) 69.1 (50.9) 15 (79) -0.2 (-0.65)

Reach 2 34 2.13 (0.04) 0.02(0.06) 4.4 (3.2) 2 (10) -0.02 (0.06)

Reach 2 33 -44.41 (-0.92) -1.02 (-3.34) -83.4 (-61.5) -19 (-100) 0.33 (1.08)

Reach 2 32 0 (0) -0.02 (0.06) -0.1 (0.07) 0 (0) -0.08 (-0.26)

Reach 2 31 -2.95 (-0.06) -0.17 (0.55) -2.6 (-1.9) 0 (0) 0.06 (0.19)

Reach 2 30 13.08 (0.27) 0.55 (1.80) 15.9 (11.7) 3 (15) -0.16 (0.52)

Reach 2 29 -13.07 (-0.27) -0.54 (-1.77) -15.9 (-11.7) -3 (-15) 0.2 (0.65)

Reach 2 28 -2.75 (-0.05) -0.26 (0.85) -1.8 (-1.3) 0 (0) -0.13 (-0.42)

Reach 1 27 0.48 (0.01) 0.01 (0.03) 0.04 (0.02) 0 (0) -0.04 (-0.13)

Reach 1 26 75.5 (1.57) 1.56 (5.11) 140.8 (103.8) 23 (121) -0.1 (0.32)

Results in Table 6 display that the velocity and hydraulic attributes of stream

flow can change between sections of a channel, even if they are located next to one

another and within a common morphological setting (like the same reach). A

decrease in flow velocity, shear stress, and stream power occurs at the transition

from Reach 3 to Reach 1, as flow enters the riprap. At the transition from Reach 2 to

85

Reach 1, where flow exits the riprap, there is a local increase in slope and subsequent

increase in flow velocity, shear, and stream power. Also, the downstream reach

having a smaller channel could produce a greater slope and hydraulic radii, and

could cause an increase in flow velocity and higher levels of shear stress and stream

power within the reach.

So, changes in local channel slope and hydraulic radius seem to control the

transitions in fluid shear stress, stream power, and flow velocity. There are no

instances of slope increases without velocity, shear and power increasing between

any of the cross-sections. With changes in shear stress being as great as is seen in

Table 11 (up to 75 pascals between adjacent cross-sections), different sediment size

classes may be transportable at one cross-section but not at the adjacent cross-section

(or vice versa). This is example of how local variations in channel slope and shape

can greatly impact local sediment movement.


Reaches

With the design of the riprap-lined reach being purposed in protecting the

remaining dam infrastructure, the ability of the riprap-lined section of the

Conococheague Creek stream channel in channeling floods (and hence protecting

the remaining dam abutments) was investigated. In this case, as seen in Figure 21,

86

the channel is much larger in width, depth and area within the riprap-lined reach

(Reach 2). Results presented in Part 1 of this study also showed that Reach 2 has the

lowest slope amongst the reaches involved in the study. So, it appears that flood

channeling may have a greater link to channel area rather than slope.

Modeling shows that this increase in channel area may lead to discharges

greater than the apparent bankfull discharge in other reaches being channeled

within the riprap-lined reach. Increasing the channel area (as seen in Figure 21)

allows for a greater discharge to be contained within the banks of the riprap-lined

reach (Reach 2). Although this is a good way of protecting the remaining dam

infrastructure, lack of floodplain activation may mean that the riprap-lined channel

could produce unnaturally high levels of shear stress within the channel during

flood events.

87

Figure 21: Comparison chart of channel geometry differences between the riprap-lined reach (Reach 2) and the adjacent, downstream reach (Reach 1). The graph depicts Reach 1 (downstream) cross-sections as blue cross-section profiles and Reach 2 (riprap-lined reach) as light red cross-sections. The red riprap-lined bathymetry sections are distinctively deeper and wider than the blue downstream sections. This is due to the design of the channel in Reach 2 and Reach 1 being behind the dam during its operation (which may have led to the channel being smaller than the nearby reaches.

Further describing the difference in channel size between the riprap-lined

reach and downstream reach, Figure 21 shows Reach 1 ranging in depth from about

0.5 meters (1.6 ft) to 1.4 meters (4.6 ft). The width of the channel in the downstream

reach (Reach 1) ranges from 6.1 meters (20 ft) to 10 meters (32.8 ft). In comparison

the depth of the riprap-lined reach (Reach 2) ranges from one meter (3.3 ft) at the

downstream extent of the riprap, to almost three meters (9.8 ft). The width of Reach

2 is also greater than the downstream reach. The width of the riprap-lined reach

ranges from 7.9 meters (25.9 ft) to 18 meters (59.1 ft).

88

Numerically observing the flood channelization upstream and downstream

of the riprap-lined reach, and within the riprap-lined reach, Figure 22 displays the

results for the flow top-width divided by the channel top-width. A minimum

possible value of one signifies complete channelization and any values greater than

one signify flooding (in number of channel widths).

Figure 22: Results of the “channelization” study conducted as Part 2 of this study. Flow channeling within the riprap-lined reach shows the channeling/flooding of all of the modeled discharges (Flow Profiles B – E shown as blue lines), within, and downstream of the riprap-lined reach. On the y-axis, channeling was determined by dividing the flow top width produced by each of the Flow Profiles by the channel top width at each of the cross-sections. All discharge levels are shown to be contained within the channel banks in the riprap-lined reach. Upstream, areas of flooding are present at all discharges above the bankfull (Flow Profile B) discharge. Downstream, all of the modeled discharges (including the bankfull discharge) produce flooding.

In Figure 22 the channeling of floods within the riprap-lined reach is

presented. Flooding exists upstream and downstream of the riprap at all discharges

greater than the bankfull discharge (Flow Profile B). Upstream of the riprap, in

Reach 3 the Flow Profile C discharge of 5.96 cms (210.5 cfs) results in flood widths

89

that are up to 5.8 times greater than the width of the channel, the Flow Profile D

discharge of 8.96 cms (316.4 cfs) results in flood widths that are up to 8 times the

width of the channel, and the Flow Profile E discharge of 9.89 cms results in flood

widths that are 9.5 times the width of the channel.

The cross-sections at the upstream and downstream ends of the riprap-lined

reach are the only sections to exhibit flooding within Reach 2 (riprap-lined reach). At

the upstream extent (cross-section 37) floods are up to three times the channel width.

At the downstream extent (cross-section 28) floods are up to five times the channel

width. In these areas there is a transition between portions of channel that exhibit

smaller channel areas, and the large channel area of the riprap-lined reach.

Downstream in Reach 1, where the channel area is smaller, flooding is

persistent at the discharge levels associated with Flow Profiles B thru E. The

bankfull discharge (Flow Profile B) causes flooding downstream that is up to 5.8

times the width of the channel. At roughly three times the discharge of the bankfull

discharge, Flow Profile E results in flooding in Reach 1 that is up to 7.1 times the

width of the channel. This level is still not as great as the maximum width of

flooding in Reach 3, where the maximum flood width is 9.5 times the channel width.

Here, results show that up to the discharge of 9.89 cms (349.4 cfs) is capable of

being completely within the banks of the riprap-lined reach. This is likely due to the

large cross-sectional area of the channel within this reach and not likely due to

90

channel slope or roughness. Channeling of floods may have an impact on levels of

shear stress, stream power, and flow velocity within the reach.

Pt. 3: Investigating the Hydraulic Effects of a Forced Pool-Riffle Morphology

Stream Restoration on Bankfull Velocity, Shear Stress, and Stream Power

Part three of this study investigated average impacts of the application of a

pool-riffle morphology stream restoration within Reach 4 on the channel bottom

elevations and bankfull levels of average velocity, shear stress and stream power.

Possible downstream hydraulic impacts were also tested, but it was quickly evident

that none existed. Here, the minimum elevation profile of the pre- and post-

restoration geometries for Reach 4 are presented, the changes in the range and

average for pre-/post-restoration scenarios is summarized, and graphs are

presented summarizing changes in the range and peak density of the observed

hydraulic parameters.

The profiles for minimum channel elevation are presented in Figure 23. In

Figure 23 it is seen that the installation of the pool-riffle structures cause local

variations in minimum channel elevation and channel slope. The series of local

changes in channel elevation have caused the bankfull energy gradient slope (or

water surface slope) to decrease slightly at bankfull levels between the pre- and

post-restoration scenarios. Prior to stream restoration, Reach 4 was generally void of

91

pools and riffles, and had an average slope of 10 meters per kilometer (52 ft./mile).

The addition of seven upstream-pointing cross vane structures, one perpendicular

cross vane, and seven bank vanes decreased the average slope in the reach to 9

meters per kilometer (47 ft./mile).

92

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93

Figure 24 and Figure 25 presents detailed profiles of the minimum channel

elevations of the pre- and post-restoration scenarios in vicinity to cross vanes (Figure

24) and bank vanes (Figure 25). The local change in minimum channel elevation

around Cross Vanes 4 and 5 are presented in Figure 24. Figure 25 shows the local

minimum channel elevation changes in association with Bank Vane 7. Figure 26

below displays the changes in bankfull water surface elevation between the pre- and

post-restoration models.

A detailed view of cross vanes 4 and 5 (CS-4 and CS-5) is seen in Figure 24 as

an example of how the geometry and slope of the channel bottom changes between

the pre- and post-restoration modeling scenarios. Locally, elevation is increased

upstream of the structure, and lowered downstream of the structure. These local

changes in elevation cause slope and hydraulic radius to vary locally too. Each of the

installed cross vane structures decreases channel slope upstream of the structure.

Slope is increased where water flows over the top of the log vane. On the

downstream end of the pool, channel slope is decreased again. So, with the

installation of each cross vane, the channel slope and hydraulic radius vary in three

areas around the cross vane structure.

94

Figure 24: Profile of minimum channel elevation of cross vanes 4 and 5 for an example of how the installation of log cross vanes changes the local shape and slope of a stream channel. In the figure, the pre-restoration elevation profile is denoted by the black, dashed line. The red profile line represents the post-restoration minimum channel elevation. Clearly observable on the downstream end of each structure is the existence of a pool, which is an area of velocity shelter for both fish and fine sediments. The local changes in elevation cause a greater variability in the flow regimes present in Reach 4, the restored reach.

Bank vanes change the local shape and slope of the channel differently than

cross vanes. Upstream of the bank vane structure the slope is decreased and

downstream of the structure the slope of the channel is increased. Whereas the cross

vane structures create varied slopes in three local areas around the structure, the

side vanes only create varying slopes in two areas around the structure. The main

effect of the bank vane is forcing the thalweg to one side of the channel, creating

lateral variations in bathymetric elevation. For example, Figure 25 displays the local

change in minimum channel elevation in proximity to bank vane 7.

95

Figure 25: Minimum channel elevation profile in the vicinity of Bank Vane 7. The profile shows an example of how the minimum channel elevation changes in pre-/post restoration modeling scenarios. The pre-restoration elevation profile is denoted by the black, dashed line. The red profile line represents the post-restoration minimum channel elevation. The bank vane is labeled in the figure as BV-7, and was represented by two cross-sections in HEC-RAS modeling. Upstream of the bank vane an increase in minimum elevation is present (creating a decrease in slope around the structure) is observed. Downstream of the bank vane channel slope is locally increased in the length behind the structure, between the pre-/post-restoration scenarios.

So, the elevation profiles displayed in Figures 25, 26, and 27 show how a

forced pool-riffle morphology stream restoration changes the modeled channel’s

elevation locally around each structure. With the associated changes in channel

elevation around each structure the slope and hydraulic radius are only impacted

locally around each of the structures. Observed in the field, with the local changes in

channel elevation sand has been deposited behind each of the cross-vane structures.

In these areas, fine sediment are sheltered from any possible scouring. Modeling

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shows that, after installation of these structures, the average flow velocity and shear

stress were lowered throughout the restored reach and the minimum levels of the

same parameters have dropped.

Of course, with the local elevational changes created by the installation of

each of the vane structures the water surface elevation will change locally in the

vicinity of each of the log structures that were installed throughout the reach. The

change in bankfull water surface elevation is presented in Figure 26. Pre-restoration

(blue line) and post-restoration (red line) profiles show local differences in water

surface elevation. This likely is also a factor in the local and reach-averaged

differences in flow velocity, shear stress, and stream power that are seen in Figures

27, 28, and 29, respectively.

Figure 26: Bankfull water surface elevation profile of Reach 4 (the restored reach) for the pre-restoration (blue line) and post-restoration (red line) water surfaces. Cross-vanes and bank-vanes are labeled as CV-# and BV-#, respectively. The perpendicular cross-vane is also labeled. The changes in water surface elevation appear to be local, centered around each of the vane structures installed as part of the forced pool-riffle stream restoration. With the changes in bankfull water surface elevation the energy gradient slope changes as well, leading to changes in shear stress and stream power levels. Though each of these variations are local, averaging them across a reach can show the general hydraulic impacts these structures may have on a reach.

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Figure 27 below displays the velocity profiles of the bankfull discharge in the

pre- and post-restoration models. Again, the vane structures are labeled similarly to

Figure 23 and 26, with “CV-#’ and “BV-#” representing cross-vanes and bank-vanes,

respectively. Modeling shows that the main result from the stream restoration was a

greater number of flow transitions and a greater number of peaks and troughs

(maximums and minimums), and that the minimum values for the range have

decreased (increasing the overall range). Around each cross-vane; upstream the

velocity tends to decrease as the slope increases, velocity increases as flow proceeds

over the top of the structure, and then slows down on the downstream side of each

cross-vane. This causes a greater number of locations at which flow velocity, shear

stress, or stream power will vary throughout the reach.

In regard to variations in velocity, shear, and stream power modeling shows

that there were 18 transitions in flow velocity throughout the reach resulting in 13

distinct peaks and troughs (maximums and minimums) of flow velocity. This leads

to the pre-restoration scenario having a peak density of 2.1 peaks per 100 meters (or

304 ft.) The post-restoration modeling scenario results in 62 transitions in flow

velocity, with 42 distinct peaks/troughs, giving the post-restoration scenario a peak

density of 6 peaks per 100 meters (304 ft.) of channel.

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Figure 27: Bankfull velocity profile for the pre-restoration (blue line) and post-restoration (red line) depicts the modeling results for velocity in the restored reach for the bankfull discharge level (Flow Profile B). Cross-vanes and bank-vanes are labeled as “CV-#” and BV-#”, respectively. The ranges of the pre- and post-restoration modeling scenarios change minimally between the two. The velocity range of the pre-restoration scenario is 0.6 to 1.6 m/s, and the range of velocities of the post-restoration scenario is 0.42 to 1.6 m/s. The average velocities for the scenarios are 1.09 m/s and 1.04 m/s for the pre- and post-restoration scenarios. Peak density increases from 2.1 to 6 peaks per 100 meters (304 ft.) of channel. An increase in peak density means more velocity transitions and greater variability in flow regimes in the reach.

Regarding the range and average of flow velocities, flow velocities of the pre-

restoration modeling scenario range from 1.6 m/s (5.3 ft./s) to 0.6 m/s (2.0 ft./s),

averaging 1.09 m/s (3.6 ft./s) throughout the reach. The post-restoration scenario

has a range of velocities from a maximum of 1.6 m/s (5.3 ft./s) to 0.42 m/s (1.4

ft./s), averaging 1.04 m/s (3.4 ft./s).

So, modeling shows that between pre- and post-restoration scenarios there is

an increase in the number of velocity transitions and peaks and troughs. Results also

show that the range of flow velocities only decreases at the minimum end of the

range and the average flow velocity only slightly decreases. This signifies how a

pool-riffle morphology restoration impacts flow velocity at this study area.

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Designed pools decelerate flow below pre-restoration levels, but the designed riffles

do not accelerate flow beyond pre-restoration levels.

Next, the restoration’s impact on the shear stress at the 2-year discharge was

studied. Similarly to the velocity, there was an increase in the number of peaks and

troughs and transitions of shear stress between the pre- and post-restoration

modeling scenarios. The shear stress comparison is seen in Figure 28, in which the

pre-restoration scenario is seen to have 17 transitions with 13 peaks/troughs

(resulting in a peak density of 2.1 peaks per 100 meters (304.8 ft.). The number of

transitions in shear stress produced by the post-restoration scenario is 63, with 46 of

those being either peaks or troughs (a peak density of 6.1 transitions per 100 meters

(304.8 ft.).

Shear stress levels associated with the 2-year, bankfull discharge range from 6

pascals (0.12 lb./ft2) to 64 pascals (1.33 lb./ft2) and averages 32.3 pascals (0.67 lb./ft2)

in the pre-restoration model. The shear stress levels of the post-restoration modeling

scenario ranges from four pascals (0.08 lb./ft2) to 66 pascals (1.37 lb./ft2), and the

average unit shear stress decreases to 29.3 pascals (0.61 lb./ft2). The slight changes in

minimum and maximum shear stress, of two pascals (0.04 lb./ft2), reflect general

changes associated with the pool-riffle morphology restoration. The change in

average shear stress, of three pascals (0.06 lb./ft2), also reflects the change in

elevation associated with the restoration.

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Figure 28: Bankfull shear stress profiles of Reach 4 for the pre- and post-restoration modeling scenarios. The figure displays the bankfull (Flow Profile B) shear stress levels associated with the pre- (blue line) and post-restoration (red line) modeling scenarios. Again, cross-vanes and bank-vanes are labeled as “CV-#” and BV-#”, respectively. The ranges of shear stress change by two pascals, with the maximum increasing by two pascals and the minimum decreasing by two pascals. In regard to the average, the average shear stress decreased by three pascals between the pre-and post-restoration modeling scenarios. Significantly, the number of shear stress transitions increases (increasing the variability of shear stress levels throughout the reach).

Between the pre- and post-restoration modeling scenarios there are also

changes in the bankfull stream power within the restored reach. Again, these

changes exist in the form of an increase in the number of peaks/troughs and

transitions in levels of stream power. The stream power associated with the pre- and

post-restoration modeling scenarios are seen in Figure 29. For the pre-restoration

scenario, there exist 18 transitions in stream power. Of those 18 transitions, 13 are

peaks/troughs. The post-restoration scenario results in 62 transitions, 47 of those

being distinct peaks or troughs.

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Figure 29: Bankfull stream power profiles for pre- and post-restoration modeling scenarios in Reach 4. Graph displays both bankfull (Flow Profile B) stream power profiles associated with the pre- and post-restoration modeling scenarios. Again, cross-vanes and bank-vanes are labeled as “CV-#” and BV-#”, respectively. Pre-restoration stream power profile is displayed in blue. The post-restoration profile is seen in red. The ranges of stream power change with the minimum decreasing by two watts, and the maximum remains the same between pre- and post-restoration scenarios. In regard to the average, the average stream power decreased by 5.7 watts per meter between the pre-and post-restoration modeling scenarios. Again, the significant result is the increase in peak density (regarding flow regimes) within Reach 4.

Also in Figure 28, the range of stream powers associated with the pre-

restoration modeling has a minimum of five watts (3.7 lb/ft s) and a maximum of

104 watts (76.7 lb/ft s) and the average unit stream power is 43.9 watts (32.4 lb/ft s).

The range of stream powers associated with the post-restoration scenario has a

minimum of 3 watts (2.1 lb/ft s) and a maximum of 104 watts (76.7 lb/ft s). The

average unit stream power of the post-restoration modeling is decreased from the

pre-restoration scenario to 38.2 watts (28.2 lb/ft s). Similarly to shear stress, these

changes in the levels of stream power are minimal and should not have any

implications toward stream stability or sediment transport.

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In conclusion, these results show how a stream restoration such as the one

installed in the upper 750 meters (2460 ft) of stream within the former

Chambersburg Reservoir footprint change the water surface elevation, flow velocity,

shear stress, and stream power within that reach. Summaries of the pre- and post-

restoration modeling scenarios and results are summarized in Figures 30 and 31.

Figures 30 and 31 summarize the results of Part 3 of this study, and regard the

hydraulic impacts of a pool-riffle morphology stream restoration. Figure 30 presents

the pre-restoration results, and Figure 31 presents the post-restoration results. Both

figures present the cross-sections (green lines), water surface extent (blue lines),

bank stations (red points), flow direction (blue arrow), and ranges and averages of

peak density, velocity, shear stress, and stream power.

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Figure 30: Results of pre-restoration modeling scenario within Reach 4. Reach dividing lines (tan lines), cross-sections (green lines), flow direction (blue arrow), bank stations (red points), and water surface extent (blue lines) are depicted in the image. Before restoration, the reach was generally void of natural pools and riffle structures. Velocity averaged 1.09 m/s, shear stress averaged 32.3 pascals, and power averaged 43.9 watts/m. Significantly, the pre-restoration scenario only generated a peak density of 2.1 transitions per 100 meters (304 ft.) of stream channel.

In Figure 30, cross-sections represent the pre-restoration scenario. Figure 31

below presents the cross-sections of the post-restoration modeling scenario. Between

the two scenarios, from pre- to post-restoration, there is an increase in the peak

density (number of flow transitions per channel length), a general decline in the

average levels of each parameter, and ranges of velocity, shear stress, and stream

power show a slight decrease in each of the minimum levels.

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Figure 31: Results of the post-restoration modeling scenario within Reach 4. Reach dividing lines (tan lines), cross-sections (green lines), flow direction (blue arrow), bank stations (red points), and water surface extent (blue lines) are depicted in the image. After restoration, the average velocity declined by 0.05 m/s. The average shear stress dropped by three pascals. The average stream power decreased by 5.7 watts/m. The peak density between the pre- and post-restoration scenarios increased by 3.9 peaks per 100 meters (from 2.1 to 6 peaks per 100 meters). The general decline in average values signifies the creation of pools throughout the reach.

The reduction in the minimum of each of the parameters observed between

the pre-restoration (Figure 30) and post-restoration (Figure 31) points to how

pool/riffle imitating structures only decrease range on the minimum end. This is

homage to pooling downstream of the structures, where velocities decrease. The

lack of increase on the maximum end of the ranges means that flow is not

accelerated (and does not reach depths) greater than the pre-restoration scenario.

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Aside from these changes seen within the restored reach (Reach 4), also

significant is the restoration’s lack of impact on Reach 3 downstream. Modeling

showed that none of the hydraulic parameters studied downstream of cross-section

82 were affected by the new pool and riffle system. This points to the effectiveness of

forced pool-riffle morphologies in only locally changing flow hydraulics, so reaches

downstream are not significantly impacted by an upstream restoration. This is a

very significant result when considering that the purpose of the stream restoration

was to create in-stream habitats for Brook Trout (or any fish), and their prey,

without harming surrounding environments.

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CHAPTER 6: DISCUSSION

Introduction

The former Chambersburg Reservoir was chosen as the study area for this

site because of its local relevance in the science of dam removals. This dam removal

site is very similar to the nearby (and currently drained) Meadow Grounds Lake and

Dam (Fulton County, PA) and Gunter Valley Dam and Reservoir (Franklin County,

PA). Each of these dams are to be removed in the future, reside in the valley-ridge

province, are of the medium earthen variety, and are in undeveloped headwater

drainage basins. Lessons learned here may prove directly applicable to their

removal.

This section, specifically, will discuss topics such as; 1) flow data estimation

and model calibration for the study area, 2) sediment transport capability by reach,

3) flood channeling, 4) riprap channel-lining, and 5) pool-riffle morphology stream

restorations. Each of these topics hold significance both in their specific topics, and

the topic of dam removal.

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Notes about estimating stream discharge from sparse data

Estimating flood discharge values for generally accepted flood recurrence

intervals proved impossible because the archive of data associated with the two

proximate USGS stream gages does not contain the necessary and sufficient time

series of paired stream depth and discharge measures. The available data for the

Conococheague Creek included 21 pairs of annual instantaneous peak depth and

discharge measurements and 21 years of daily mean discharge statistics. These

instantaneous peak data are necessary for characterizing the largest storm events but

insufficient for revealing the frequencies of base-level conditions, bank-full

conditions or recurring flood events. The daily statistics are more useful for

revealing the frequency of recurring flood events, but, as both Table 7 and Figure 32

clearly show, they do not (and cannot) represent any of the observed peak events.

During the 20-year period shown in Table 7, for example, the smallest percent

difference between instantaneous peak measure and daily mean statistic was -11.3

percent; the largest underestimation was -71.6 percent.

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Table 7: Differences between mean daily discharge statistics and annual instantaneous peak discharge measures for the Conococheague Creek stream gage 01614090. Table shows instantaneous peak data discharge/stage and the associated date for that discharge. Each instantaneous data-point is compared to the mean daily discharge for the same day. The summary of this is presented in Figure 31 below.

m ft cms cfs cms cfs

1970 Jul. 09, 1970 0.8 2.61 2.61 92 0.74 26 -71.6

1979 Jan. 24, 1979 1.04 3.4 10.9 385 3.62 128 -66.8

1973 Sep. 14, 1973 0.74 2.43 2.04 72 0.71 25 -65.2

1961 Apr. 16, 1961 0.85 2.8 3.23 114 1.22 43 -62.2

1981 Feb. 23, 1981 0.99 3.25 6.51 230 2.58 91 -60.4

1977 Oct. 09, 1976 1.05 3.44 10.82 382 4.39 155 -59.4

1966 Sep. 14, 1966 0.66 2.17 1.33 47 0.59 21 -55.6

1978 May. 14, 1976 0.83 2.71 2.83 100 1.33 47 -53.0

1963 Nov. 10, 1962 0.77 2.54 2.32 82 1.1 39 -52.6

1974 Apr. 04, 1974 0.87 2.85 3.65 129 2.12 75 -41.9

1976 Oct. 18, 1975 0.8 2.63 2.58 91 1.53 54 -40.7

1969 Nov. 18, 1968 0.57 1.86 0.65 23 0.42 15 -35.4

1965 Mar. 05, 1965 0.75 2.46 2.15 76 1.44 51 -33.0

1962 Mar. 22, 1962 0.73 2.41 1.95 69 1.42 50 -27.2

1967 Mar. 07, 1967 0.68 2.24 1.5 53 1.16 41 -22.7

1968 May. 29, 1968 0.8 2.64 2.72 96 2.12 75 -22.1

1972 Jun. 22, 1972 1.05 3.45 11.1 392 8.66 306 -22.0

1964 Apr. 30, 1964 0.76 2.48 2.21 78 1.78 63 -19.5

1971 Feb. 23, 1971 0.68 2.23 1.47 52 1.3 46 -11.6

1975 Sep. 26, 1975 1.05 3.45 11.1 392 9.85 348 -11.3

Percent

difference

USGS stream gage 01614090

Year

Date of

Instantaneous

Peak Measures

Instantaneous

Peak Stage

Instantaneous

Peak Discharge

Mean Daily

Discharge

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Figure 32: Differences of instantaneous peak discharge and mean daily discharge levels for the Conococheague Creek stream gage (01614090). The average difference (or 1.77 cms, or 65 cfs) is depicted as the black line, and the difference between a peak discharge measurement and its mean daily counterpart are depicted by blue diamonds. Although mean daily data was collected for the gage the fact that it underestimates discharges of peaks associated with precipitation events means that mean daily discharge data cannot be used to accurately estimate discharge recurrence intervals.

The available data for the Birch Run Creek are sparse and include only two

pairs of depth and discharge measurements and five unpaired in-stream discharge

measurements. No method exists for building a reasonable hydrograph from the

data available for these two stream gages, so it was impossible to estimate flood

discharge values for generally accepted flood recurrence intervals. That is why,

instead, this study considered five plausible flood scenarios.

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Notes about calibrating the HEC-RAS model

Lack of site-wide associations between flow depths and discharge rates meant

that the model was not able to be calibrated for the study area, and that model

accuracy cannot be confirmed across the site. This may lead to results of this study

(and their interpretations) being limited in the level of accuracy that is currently

determinable. The available data for instantaneous annual peak discharge rates (and

associated depth data) for the USGS stream gage on the Conococheague Creek

allowed the model to be calibrated at the upstream modeling extent on the

Conococheague Creek, but nowhere else. With this being the case, the assessment of

modeling result accuracy that was calculated in Chapter 5 only applies to the USGS

stream gage on the Conococheague Creek.

Again, the depth accuracy assessment that was performed for each of the

modeled discharges determined that the Conococheague Creek stream gage was

modeled with an average accuracy of about 3% of the depth across the modeled

discharges. This did not take any adjustment of parameters within the HEC-RAS

model, so the depth/discharge relations for each of the five reaches in the study area

could possibly be as accurate. But, even with good modeling accuracy at the

Conococheague Creek USGS gage, without considerable field work (including

depth/discharge measurements for cross-sections within each reach, across the

range of modeled discharge rates) the degree of accuracy within each of the study

reaches is not calculable. So, to increase the degree of accuracy of this study, future

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work should be conducted so that the modeling calibration and accuracy can be

reported on for each reach within the study area.

Sediment Size Transport by Reach

Throughout the increase of discharge levels from Flow Profiles A to E there

exist relations between reaches (Reach 1 thru 5) and sediment size capable of being

transported. Generally speaking, Reach 2 (the riprap-lined reach) transported the

smallest-sized sediments. The forested Reaches 1 and 5 transported the largest

sediment size classes. Of these, Reach 1 is the portion of channel between the dam

and spillway prior to dam removal. Reaches 3 and 4 fall in the middle of sediment

transport size ranking. Discrepancies in sediment transport capabilities between

adjacent reaches (or cross-sections) can cause local, or reach-wide, channel

instabilities.

For example, between Reaches 1 and 2 of the study area the sediment size

transport capabilities vary moderately. At Flow Profile C of 5.9 cms (208.1 cfs) the

maximum grain size transportable by Reach 1 is very coarse gravel, and for Reach 2

is coarse gravel (refer to CHAPTER 5: RESULTS, Flow Profile C). So in the case of

this level of discharge, sediment that is coarse gravel-sized (and smaller) will be

supplied to Reach 1 by Reach 2. This sediment, because it is smaller than the

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maximum size of transportable sediment in Reach 1 will continue to be transported

throughout Reach 1.

Different levels of fluid shear stress produced between adjacent reaches may

also have a control on the sorting of sediment within a given reach. When flow

transitions between reaches (from one reach to the adjacent, downstream reach) and

the average shear stress decreases there exists an opportunity for depositional

sorting to occur. As flow transitions from Reach 3 to Reach 2, at steady-state flow

(which is modeled here) very coarse gravel will drop out of transport (in Reach 2)

because the fluid shear stress drops below the critical shear stress level of coarse

gravel in Reach 2.

Differences in the sediment-size being supplied between reaches has larger

connections to morphology (channel shape and bedform) and channel stability. A

reach-based analysis such as this generalizes the sediment transport capabilities of a

reach in a similar fashion as many sediment budgets do. Since hydraulic parameters

such as shear stress, flow velocity, and stream power can vary significantly locally,

averaging parameters helps scientists understand the complex systems that streams

are.

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Flood Channeling

When an earthen dam is partially removed, such as the case of the v-notch

breeching of the Birch Run Dam, the remaining dam abutments must be protected

from being eroded. The remaining dam abutments are massive sediment sources

that could potentially be scoured during flooding. So, during an earthen dam’s

removal process, the design of a reach that is able of channeling floods between the

remaining dam abutments decreases the risk of sediment erosion due to flood

scouring.

In description of how the riprap-lined reach channels floods between the

remaining dam abutments, Part 2 of Chapter 5 describes results of the numerical

study of flood channeling capabilities of the riprap-lined reach. This reach has one

major goal; to protect the remaining dam infrastructure. To do this, the design of the

reach does two things; 1) abates lateral channel erosion, and 2) channels floods

throughout the reach. To channel floods, the main requirement is the required

channel area.

Referring back to Figure 21 on page 88, the main difference between the

cross-sections of Reach 1 (the downstream reach) and Reach 2 (the riprap-lined

reach) is the size. The riprap-lined reach (Reach 2) is much larger in width and

depth, and thus area. All Flow Profiles considered in this work were channeled in

Reach 2. In Reach 1, within which widths, depths, and areas were smaller, floods

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were resultant from Flow Profiles B – E (3.02 cms to 9.89 cms). So, with a local

variation in channel size there is a change from cross-sections at which flow is being

channeled to cross-sections exhibiting flooding.

This result points toward the importance of cross-sectional channel area in

flood channeling. With greater depth and width, and less floodplain accessibility the

volume of water that is able of being contained within Reach 2 is greater than is able

to be contained within Reach 1. A great example of the discrepancy in channel area

is seen in Figure 33. The left image presents the representative image of Reach 1 (see

Chapter 2: Study Area) and the right image presents a representative image of the

riprap-lined reach (Reach 2). For scale, humans are present in each. In the image of

Reach 1 (left) the depth of the channel is up to the human’s waist. Within the riprap-

lined reach (Reach 2 pictured in the right image), the depth of the channel is greater

than the entire height of the human pictured within the channel.

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Figure 33: Comparison of representative images between Reach 1 and Reach 2 (the riprap-lined reach). The blatant difference in channel depth and width is obvious when comparing channel depth to the height of a six foot human. In each image in Figure 31 a 6-foot-tall person is labeled. Within Reach 1 the depth of the channel reaches about three feet deep, whereas in Reach 2 the channel depth reaches up to nine feet. The relatively large cross-sectional channel area is likely one significant factor in the ability of the riprap-lined reach (Reach 2) to channel floods and protect remaining dam infrastructure.

Again, as in Figure 33 above, it is the size of the channel area that appears to

be a major factor in flood channeling and not the presence of channel armoring or

aggressively steep channel slopes. So, in conclusion, the greater the cross-sectional

area of the channel the greater the flood channeling capabilities of that reach will be.

When it comes to preventing scouring (of remaining earthen dam infrastructure)

due to flooding, the greater the flood channeling capabilities within the area of the

former dam, the better.

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Riprap Channel-armoring

Channel armoring, like Flood Channeling, is one way Reach 2 (the riprap-

lined reach) protects the remaining dam infrastructure from erosion. Channel

armoring abates lateral channel erosion. In this case, a stable channel means the

channel won’t erode into one of the remaining dam embankments. So, on short-

term, the riprap protects infrastructure from erosional scouring during flood events,

and on long-term inhibits the channel from eroding into one of the remaining dam

abutments.

Riprap is capable of preventing lateral channel erosion due to its

tremendously high critical shear stress. By design, riprap boulders are meant to stay

in place during even large discharge events. Boulders at the site, although the exact

level of critical shear stress is not known, require fluid shear stresses of at least 112

pascals (2.3 lb./sq. ft.). Modeled discharges produce a maximum average of 59.2

pascals (1.25 lb./sq. ft.). The shape and slope of the riprap-lined reach (Reach 2)

produces a maximum shear stress of 32.9 pascals (0.68 lb./sq. ft.). So, at the modeled

discharges, which represent naturally occurring flows, shear stress levels produced

do not present any possibility of transporting the riprap boulders.

So, riprap channel-armoring proves a cost-effective solution to the need of

protecting remaining dam infrastructure following a removal. Riprap is designed to

stay in place during flood events, and leads to riprap boulder-armoring being a

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possible effective, long-lasting solution when channel armoring is necessary. Here,

in the case of the Chambersburg Dam removal, the shape and slope of the riprap-

lined reach produce shear stress levels that are lowest of all the reaches within the

study area (Reaches 1 – 5).

Pool-Riffle Morphology Stream Restorations

Pool-riffle stream morphology stream restorations introduce more natural

stream morphologies (i.e. a sequence of pools and riffles) to reaches of channel

formerly void of natural channel forms. The major hydraulic change in the area of

these structures appears to be on the downstream side of the structure. Downstream

of structures, behind the upstream-pointing logs finer sediments are shielded from

high flow velocities that would otherwise scour them away and transport them

downstream. This introduces fine sediment deposition in reaches that were formerly

void of sand deposition.

Figure 34 is an image captured during surveying of cross-vane five within

Reach 4 (the reach of pool-riffle restoration). The significant aspect of this image is

the area of sandy deposit in the pool behind the vane. The area of sand deposit in

the pool is outlined and labeled. The local variance of sediment size is also noted by

the existence of both cobbles (outlined and labeled in Figure 34) and sands in close

proximity to one another within the stream channel.

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Figure 34: Image of cross vane five within the restored reach (Reach 4). Deposition of sandy sediments in the pool behind the cross vane structure is outlined in white and labeled. To image left, an area of streambed dominated by cobbles is labeled. Surveying pole is placed on lower portion of the log vane for scale. Of major note is the local variation in sediment size, between sands and cobbles. The local variation of sediment size within such a short distance is one of the major channel improvements associated with the installation of vane structures. These structures, shield fine sediments from scouring at flood discharges and provide resting areas for fish, and sandy sediments deposited behind them provide habitat areas for macroinvertebrates.

Prior to installation of the cross vane structure in the area of channel pictured

in Figure 34 would have been comprised of predominantly cobbles. Now, there

exists a greater local variation in sediment size in the vicinity of each of the seven

upstream pointing cross vanes. Each of these structures; 1) shield fine sediments

from scouring at flood discharges, 2) provide resting areas for fish, 3) direct the

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thalweg toward the center of the channel as flow proceeds over the structure, and 4)

provide habitat areas for macroinvertebrates in sandy sediments deposited behind

them.

With sandy deposition around each of these structures, there is likely to be

net deposit of sandy sediments, both locally and reach-averaged. Because the sand

storage volume behind each cross-vane structure is relatively small, sand transport

should fairly quickly reach a general equilibrium throughout the reach and no

significant impact should be observable within the downstream reach. In a worst

case scenario, for example, if a large volume of sand were able to be stored behind

each structure the cumulative volume of sand storable throughout the restored

reach would not be transported to the reach downstream. Downstream, this could

likely lead to sediment sorting that trends toward a bed comprised of a majority of

cobbles. Over time, pools would eventually will with sandy sediment and natural

sand transport levels would be restored to the reach adjacent and downstream.

That being said, the cross-vane structures installed as part of the pool-riffle

restoration of Reach 4 of the Conococheague Creek within the former footprint of

the Chambersburg Reservoir only store a small volume of sandy sediment. The

relatively small impact should pass quickly, as pools appear to have filled (at least

partly) with sandy sediment since the installation of the restoration in 2013. So, this

points to how cross vanes are successful in introducing more variable regimes

(hydraulic, sediment, and biologic) throughout reaches that are restored, without

120

having any apparent hydraulic impact (and only a possible minor impact on sandy

sediment availability) to the reach adjacently downstream.

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CHAPTER 7: CONCLUSIONS

Introduction

It is no longer a new trend, dams across the United States are being removed.

Their purposes are being re-evaluated, and in cases where dams are dangerous,

harmful to nature, or serve no purpose, decisions to remove dams are becoming

more and more popular. Although the trend of removals is gathering momentum,

the monitoring of post-removal/restoration projects has not been granted the same

attention. The long-term state of dam removal sites, due to the relative youth of dam

removals, is a topic that has not been heavily studied. So, the results and conclusions

gained here, which show the state of an earthen dam removal roughly eight years

after its removal was completed, should be very valuable toward the restoration of

dam-removal-impacted stream channels.

This study tried to accomplish two things: perpetuate long-term monitoring

of the Birch Run Dam removal site, which was started by Manuel (2009a,b); and

answer new research questions regarding stream restoration methods at the site.

This chapter summarizes what was learned.

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This study modeled five reaches and five stream discharge scenarios that

could transport the most dominant bed material classes that have been observed at

the site. This section summarizes lessons learned from the results of the “Sediment

Transport Capability Assessment” section in Chapter 5: Results.

Reach 1

Reach 1 was the segment of the Conococheague Creek that was between the

Birch Run dam and the spillway that directed overflows around the dam (Refer to

Figure 4). This reach of stream was not subjected to natural flow regimes over the

dam’s operational lifespan. Now, this section of channel has abundant woody

debris, signs of bank erosion (slumping and treefalls), and sandy sediment deposits

on floodplains that are well-connected to the channel.

Modeling results show that Reach 1 exhibits the highest levels of shear stress

and is capable of transporting the largest sediment classes (fine cobbles).

Throughout modeling, Reach 1 exhibited sediment transport capabilities that were

higher than Reach 2 in 4 of 5 Flow Profile scenarios. This means that, at 4 of the 5

modeled discharges, Reach 1 was the most susceptible to erosional scouring of fine

cobbles. Additionally, at discharge rates greater than the bankfull discharge

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(selected to fill the channel of Reach 5) the downstream Reach will be susceptible to

net sediment loss, or erosion.

Reach 1 had the lowest slope of the five reaches and the smallest channel

area. This reach also exhibited the largest hydraulic radius during each of the

modeled flow scenarios (Flow Profiles A – E). Flooding is persistent at every cross-

section within this reach at bankfull discharge levels just above 3 cms (Flow Profile

B). Compared to the other four reaches studied, this reach floods more than any

other during modeling.

The deposition of sand on the banks of Reach 1 points toward one of the

benefits of good floodplain connectivity downstream of dam removals. Floodplains

that are frequently active are more capable of storing sediment (either legacy

sediment from within the reservoir, or sediments disturbed by the removal process).

This portion of channel likely may have good floodplain connectivity because; 1) it

has a generally low slope, 2) the channel is smaller in cross-sectional area, and 3) the

presence of woody debris. This combination of circumstances fosters frequent

floodplain activations that, in this reach, can transport up to small cobbles and

deposit sand-sized sediments on the floodplains.

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Reach 2

Reach 2 is the riprap-lined reach that was designed (prior to the removal

process) to protect the remaining dam infrastructure. This reach includes 150 meters

of riprap channel lining, and is designed to channel floods and prevent erosional

scouring. The relatively large cross-sectional area of this reach of channel is

necessary to channel floods, and is greater than the cross-sectional area of any of the

other reaches. This reach, because of its riprap-armoring, will likely not change

shape over time. In this numerical study, Reach 2 channeled all five flood scenarios

(Flow Profiles A-E) and, in general, exhibited the lowest sediment transport

capability of the five reaches.

Reach 2 produces the lowest shear stress levels and transports the smallest

sediment class at each of the five modeled discharges, which may cause net

deposition within this reach. The water surface slope of Reach 2 is lowest of the five

reaches at discharges greater than that of Flow Profile A. The channel in this reach

has the lowest hydraulic radius, and lowest slope. Even during channeling of flood

discharges up to 9.89 cms (349.4 cfs) Reach 2 does not produce shear stresses that are

greater than any of the other modeled reaches.

The riprap channel design within Reach 2 is generally successful because; 1)

riprap is fairly cost-efficient, 2) the shape of the channel in Reach 2 channels floods

and protects the remaining abutments during floods, 3) the riprap boulders further

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protect remaining abutments from scouring and prevent channel from eroding, and

4) has a relatively small environmental impact. Although riprap is not completely

natural, the overall purpose of the riprap is to prevent the stream from eroding the

massive volume of sediment stored in the remaining dam embankments. This

riprap-lined channel has seemingly done its jobs since the dam was removed in

2005.

Reach 3

Reach 3 is one of two reaches (along with Reach 4) to be inundated by the

reservoir during the dam’s operational period. When the dam was built, Reach 3

was filled with sand to divert water to a channel servicing the dam’s intake. When

the dam was removed, the sand was also removed and the channel was restored to

its’ original path. Now, this reach of channel flows between the silt cap deposited

behind the dam (on the northwest floodplain) and spoil pile (on the southeast

floodplain). Reach 3 is located downstream of the pool-riffle morphology restoration

(Reach 4) and upstream of the riprap-lined reach (Reach 2). Reaches 3 and 4 display

similar measures of slope, hydraulic radius, and produce similar levels of shear

stress; meaning that they may be at a general erosional equilibrium when compared

to one another.

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During flood discharges (Flow Profiles C –E), the average shear stress

produced by Reach 3 (and Reach 4) falls in the middle of the studied reaches,

producing a greater average shear than Reach 2 but lesser shear stress than Reaches

1 and 5. The channel in Reach 3 produces a very similar hydraulic radius at all of the

modeled discharges. Within the floodplain to the northwest of the channel in this

reach, a wetland has formed in the area of the former silt cap on the northwest

floodplain (likely due to the area’s low elevation). So, during the modeled flood

discharges (Flow Profiles C – E) both the silt cap and wetland are inundated by

flooding from the Conococheague Creek.

As the presence of the spoil along the southeast floodplain of this reach poses

a massive threat of sediment pollution to the Conococheague Creek, the interaction

of floods and the spoil is also very important. Modeling results showed that flooding

reaches the base of the spoil at cross-sections 56 and 57 during discharges 5.9 cms

(208.1 cfs) and above. Although this result is not ideal the re-vegetation of the spoil

pile (since the dam was removed) should mitigate the threat of scouring during

flooding. Of the two reaches that were formerly inundated Reach 3 exhibits more

areas of flooding, a slightly lower average hydraulic radius and lower average shear

stress.

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Reach 4

Reach 4 is the second of two reaches (along with Reach 3) that was inundated

by the former reservoir. This reach is 750 meters (2460 ft.) in length, partially flows

over the deltaic deposit (from the dam’s operational period), and was most recently

subjected to a pool-riffle restoration in 2013. The restoration utilized log structures

(seven upstream pointing cross vanes, one perpendicular cross vane, and seven

bank vanes) to imitate pools and riffles and increase the variability of flow regimes

throughout the reach. In the Sediment Transport Capability Assessment, Reach 4

was modeled with the restoration geometry inserted. Flooding throughout Reach 4

is not common. Four small areas exhibit flooding, and the extent of flooding does

not change greatly between Flow Profiles C and E.

Of the five modeled reaches Reach 4 is most similar to Reach 3, the other

reach inundated by the former reservoir. Of the two reaches formerly inundated by

the dam, Reach 4 produces slightly greater average shear stress levels, has a slightly

greater average hydraulic radius, and has a slightly greater slope. Producing shear

stress levels that are very similar to one another, Reaches 3 and 4 are capable of

transporting the same-sized sediment for all of the modeled Flow Profiles.

During discharges of at least 8.7 cms (307 cfs), because the upstream Reach 5

is capable of transporting fine cobbles and Reach 4 is only capable of transporting

very coarse gravel, Reach 4 may be susceptible to deposition of fine cobbles

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transported from Reach 5. This may lead to the filling in of pools constructed behind

cross-vanes or aggradation of riffles upstream of cross-vanes, and the longevity of

the project being jeopardized.

Between the pre- and post-restoration models, the pre-restoration channel in

Reach 4 exhibited a slope of 10 m./km. (52 ft./mi.). After restoration, the same reach

exhibited an average slope of 9 m./km. (47 ft./mi.). This reduction in average

channel slope displays the general effect of the installation of pool-imitating

structures decreasing the local channel slopes local to each structure.

Reach 5

Reach 5 is likely the most natural of the reaches included in this study area,

being upstream of the former reservoir. Reach 5 is comprised of natural pools and

riffles, few boulders, and densely vegetated banks in areas. Floodplain connectivity

is low in this reach when compared to the others, as flooding only occurs at three

cross-sections within this reach (at Flow Profiles D and E). Channel slope is steepest

in this reach (at 12 m/km, or 63 ft/mi) and hydraulic radius is second greatest only

to Reach 2. These results lead Reach 5 to produce an average shear stress that is

second highest across the site (to only Reach 1). Although shear and slope between

Reaches 1 and 5 vary slightly the sediment transport capability of both reaches are

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the same, as both reaches are capable of transporting sediment fine cobble-sized

material and smaller during simulations of Flow Profiles D and E.

The fact that Reaches 1 and 5 are similar in modeled levels of shear stress

(and thus sediment transport capability) may be significant because both reaches

were left forested (while Reaches 3 and 4 were deforested) when the dam was built.

Now, Reaches 1 and 5 have similar average slopes, flow velocities, shear stresses,

and transport similarly-sized sediments. This may show that, even though the slope

and hydraulic radius of two reaches is different the sediment transport capabilities

may be similar.

Part 1: Bankfull Shear Stress, Stream Power, Flow Velocity, Slope, and Hydraulic

Radius Within and Adjacent to the Riprap-lined Reach

How do approximate bankfull measures of channel slope, hydraulic radius, shear stress and

stream power taken from the riprap lined reach compare with measures taken from adjacent

reaches?

Bankfull measures of channel slope, shear stress, and stream power within

the riprap-lined reach are less than those of the adjacent reaches (Reach 1 and Reach

3). But, the hydraulic radius of the riprap-lined reach is larger than both adjacent

reaches (Reach 1 and 3). Also, levels of flow velocity, shear stress, and stream power

did not show any significant increase or decrease as flow proceeds through the

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riprap-lined reach. Levels of flow velocity, shear stress, and stream power tend to

vary with the slope and hydraulic radius of the channel.

Generally speaking, the slope of the riprap-lined reach is less than the

adjacent reaches. The apparent bankfull hydraulic radius of the riprap-lined reach is

slightly greater than either adjacent reach. The relatively low slope and slightly

higher hydraulic radius lead the riprap-lined reach to have a lower shear stress than

either adjacent reach. Velocity between the reaches is very similar and only varies by

0.1 m/s (0.3 ft/s), and because of this the resultant stream power of the riprap-lined

reach is also less than the stream power levels present in the adjacent reaches.

The cross-section to cross-section analysis (results seen in Table 6, pg. 85)

shows that flow velocity, shear stress, and stream power do not consistently increase

or decrease as flow proceeds through the riprap-lined reach. Flow velocity, shear

stress, and stream power tend to differ as slope of the channel does. Normally, if

slope increases between two cross-sections, then the velocity, shear stress, and

stream power all increase. Hydraulic radius has the opposite relation with velocity,

shear stress, and stream power. Typically, if hydraulic radius increases between two

cross-sections, then the velocity, shear stress, and stream power decline. Most

significantly, as flow enters the riprap-lined reach it decelerates and loses shear

stress and stream power (between cross-sections 37 and 36). Also, as flow exits the

riprap-lined reach it accelerates (between cross-sections 27 and 26).

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So, bankfull measures of hydraulic radius within the riprap-lined reach are

greater than the adjacent reaches. On the other hand, bankfull measures of energy

gradient slope, shear stress, flow velocity, and stream power are lower within the

riprap-lined reach in comparison to the adjacent reaches (Reach 1 and Reach 3). As

flow proceeds through the reach levels of shear stress, flow velocity, and stream

power do not increase or decrease steadily. Levels of shear stress, flow velocity, and

stream power tend to differ locally with changes in slope and hydraulic radius. In

general, when the slope between cross-sections increases so do the levels of shear

stress, stream power, and flow velocity (and vice versa).

Part 2: Flood-channeling Capability of the Riprap-lined Reach

How does flood channelization compare between the riprap-lined reach and the adjacent

reaches?

All of the modeled discharges (Flow Profiles A – E) were capable of being

channeled within the riprap-lined reach. Of those discharges, Flow Profiles B thru E

caused flooding downstream (in Reach 1) and Profiles C thru E caused flooding

upstream (in Reach 3). Modeling shows that floods up to 9.89 cms (349.4 cfs) in

discharge are capable of being channeled within the riprap. Although the riprap

channel-lining does not allow the channel to naturally erode it successfully protects

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the remaining dam infrastructure and channel banks from erosional scouring during

flood discharges.

The channeling of the modeled flood discharges within the riprap-lined reach

shows that the dam infrastructure is well-protected in the case of precipitation

events. Even with the channeling of floods, levels of shear stress within the riprap-

lined reach are the lowest across the site. This shows that, even with protecting the

remaining dam infrastructure by channeling floods, sediment transport through the

reach does not result in any adverse sediment transport conditions. The level of

flood channeling determined here is not due to the presence of riprap channel-

lining, but the size of the channel.

Part 3: Impacts of Pool-Riffle Morphology Stream Restorations

How does the newly installed pool-riffle system at the upstream end of the former reservoir

affect bankfull measures of slope, shear stress, flow velocity, and stream power of the restored

reach and the adjacent, downstream reach?

The installation of a pool-riffle morphology stream restoration within Reach 4

of the study area causes slightly lower average levels of bankfull slope, shear stress,

flow velocity and stream power. Also, the installation of this specific system does

not impact the hydraulics of the reach that is adjacently downstream (Reach 3). Most

significantly, the number of changes in levels of shear stress, flow velocity, and

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stream power increases from a peak density of 2.1 to 6 peaks per 100 meters (304 ft.)

of channel. This increase in peak density points to the effectiveness in this type of

restoration in increasing the variability of flow regimes in restored reaches.

Increasing the variability of the flow regimes within the reach will, over time,

increase the variability of sediment sizes present throughout the reach as well.

Within this reach, flow regimes are modeled to be more variable because of

the local changes in channel elevation (and slope) associated with each of the

installed pool/riffle-imitating structures. Averaged along the entire length of the

reach, between the pre- and post-restoration modeling scenarios the slope of the

restored reach decreases by 1 meter per kilometer of channel length. This change in

average slope throughout the reach points at how the restoration of the channel

creates pools (with lower channel slopes) that cause shear stress, flow velocity, and

stream power to decrease in the areas of pooling.

Each of the local changes in channel elevation (and thus slope) associated

with the installation of each structure cause changes in shear stress, stream power,

and flow velocity in the vicinity of each structure. The main change in flow behavior

is the presence of pooling behind each of the cross vanes. For each of the parameters

tested (shear stress, flow velocity, stream power and slope) the minimum levels of

each were lowered by the installation of the pool-riffle morphology. The maximum

levels for each of the parameters did not change, or very minimally decreased.

134

So, results show how pool-riffle morphology stream restorations generally

impact levels of shear stress, flow velocity, stream power, and slope throughout a

restored reach. Shown here, levels of these parameters are slightly lowered

throughout the reach, but the same parameters are not impacted within the adjacent,

downstream reach. In conclusion, the installation of a pool-riffle restoration in Reach

4 leads to increased peak densities (leading to increased flow and sediment regimes

within the reach) and lower average values of shear stress, flow velocity, stream

power, and slope within the restored reach.

Significant Conclusions for the Practice of Dam Removal

This section highlights some of the significant points and summarizes key

lessons regarding the Birch Run Dam removal so future removals can be conducted

using this knowledge and further research can be done knowing the most significant

of the aspects of this removal. There are many important aspects to this dam

removal, including; dam type, breaching plan, spoil handling, and restoration

methods. From prior research (Johnston et al. 2007; and Manuel, 2009a; 2009b), and

this research, some of the significant lessons have been:

1. The removals of any sort of earthen dam will result in the production of

“spoil.” The storage of spoil “on-site” greatly reduces the cost and

135

environmental impact of a dam removal. If spoil is chosen to be stored on-

site, then it should be positioned as far away from floodplains as possible,

and graded to minimize the possibility of slides. The removal plan for the

Birch Run Dam produced 80,600 cubic yards (61,620 m3 or 2,175,000 ft3) of

spoil, which in this case was handled entirely on-site, and included

positioning of spoil outside of the 15-year flood extent (which has thus far

proven sufficient as no erosional scouring of the spoil has been observed).

2. Handling spoil on-site can also eliminate falling hazards around remaining

dam infrastructure that is not removed as per the removal plan. At the Birch

Run Dam site, aside from lining the southern rim of the former reservoir with

spoil, spoil was also stored in the former spillway, on top of the remaining

dam, and in the former control tower. The use of the spillway and former

control tower as spoil storage minimized the fall risk associated with each

structure.

3. Partial dam removal (such as the “notch” breaching used in the removal of

the Birch Run Dam) can be used effectively to restore the passage of natural

flow regimes, reduce the volume of spoil produced, and limit associated

costs. Because the removal is partial, however, a possibility exists for future

floods to damage the remaining infrastructure (or scour the sediment if the

dam is earthen) which may require protection in the form of riprap or plastic

136

sheeting. In the case of the Birch Run Dam, the remaining dam infrastructure

was armored with riprap at the lower 4 feet to ensure the dam would not be

scoured in the case of flooding. So far, no evidence of scouring has been

observed.

4. The restoration of the stream channel to its original historic position will, over

time, minimize the tendency of the stream channel to meander back to its

historic path. A strategy such as this makes restoring the stream channel to its

original path, shape and size easier rather designing an entire new channel

path. Prior to realigning the stream, any sediment should be removed to

avoid excessive sediment pollution after the stream channel realignment.

Within Reach 2 of the study area, channel realignment was aided by the

placement of two short lengths of riprap and plastic armoring to block the

channel that used to lead to the dam’s outlet works, and ensure the channel

would not erode toward the channel or mobilize and trapped legacy

sediment.

5. Although not considered in this study, native species can be used to

revegetate the newly exposed valley-bottom and, hence, secure any newly-

exposed legacy sediment. The former Chambersburg Reservoir site (mainly in

the area of Reach 3) was planted with trees the summer after removal. Those

137

saplings are maturing; their root systems are protecting the loose spoil and

lacustrine sediments on the valley floor and fostering pedogenesis.

6. Riprap channel lining can be used to effectively inhibit lateral channel erosion

and protect remaining infrastructure from scouring during flooding. As

observed and modeled in this study (i.e., Reach 2), large channel cross-section

areas can control large discharges, but careful attention should be paid to

how large flows will enter and leave riprap lined reaches. In this case, large

and deeply channelized flows that exit the riprap-lined reach can have

elevated sheer stress levels that prompt erosion and deep scouring to occur

immediately downstream. Such downstream impacts may be necessary to

prevent earthen dam remnants from being undercut and transported.

7. The activation of floodplains and deposition of sediment on floodplains in

Reach 1 potentially shows the importance of channel-floodplain connectivity

in sediment storage after a dam removal. Although the reason for flooding

isn’t directly investigated in this work, Reach 1 appears to be smaller in cross-

sectional area and has abundant woody debris. So, those two factors may

contribute to the frequent activation of the floodplains in Reach 1. In this case

sandy sediment is deposited on the floodplain after large flows recede, which

may point to the importance of floodplain connectivity in storing sediments

downstream of dam removals.

138

8. Repetitive, post-removal monitoring is scarcely conducted. The long-term

effects of dam removals are still not fully known, especially in cases where

stream restoration plans are implemented years after removal. Here, after

dam removal in 2005, the upper 750 meters (2460 ft) of Conococheague Creek

stream channel were restored in 2013 using a pool-riffle morphology scheme.

This restoration reduced average slope, flow velocity, shear stress and stream

power in the restored reach while having no hydraulic impact on the

downstream reach. With the relatively small number of monitoring projects

conducted to date, the subjects of both post-dam removal monitoring and

post-stream restoration monitoring can never be devoted enough attention.

9. The data and information documented and the lessons learned during this

study can be applied to the nearby and currently drained Meadow Grounds

Lake (Fulton County, PA) and Gunter Valley Reservoir (Franklin County,

PA). Both were long and linear reservoirs that were impounded behind

medium-sized earthen dams, which are to be removed, in the Appalachian

Highlands region.

In conclusion, what is summarized here about the former Birch Run Dam and

Chambersburg Reservoir site can certainly be applied locally toward other dam

139

removal sites and, perhaps, more broadly toward the evolving fields of dam

removal science and stream restoration practice. This work expands upon the

baseline reports developed by Manuel (2009a, b) and contributes new knowledge

about how two stream restoration tools – riprap armoring and pool-and-riffle

system installation – influence fluid sheer stress dynamics in a mountain stream.

That said, this work was made more difficult than it needed to be by the lack of any

reported fluvial geomorphological study during and immediately after dam

removal and a sparsely populated archive of historic stream stage and discharge

data for the streams in question. What is clear, to this author at least, is that this kind

of long-term monitoring work needs to be initiated before reservoirs are drained and

not after stream restoration activities have occurred post-dam removal. More

knowledge can be created and more lessons can be learned if the entire timeline is

studied.

140

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146

APPENDIX A: Glossary

Physical Properties

Density of H2O (ρ): density of water, 1000 kg/m3

Unit Wt. of H2O (𝛾) (N/m3): standard weight of water in Newtons per cubic

meter, 9,806 N/m3

Density of Quartzite Sed. (ρ): density of quartzite sediment, 2700 kg/m3

Modeling Parameters

Area (m2): Area of active flow, in meters squared (m2)

E.G. Slope (S): The slope of the water surface between two cross-

sections

Left/Right Overbank (OB): The area of flow outside the main channel bank

station on either the left or right floodplain.

Hydraulic Radius (R): can be defined as R = A/P, the area of flow

divided by the wetted perimeter

Main Channel Bank Stations: Bank stations dividing cross-sectional profiles into

left overbank, main channel, and right overbank

for the separation of conveyance calculations due

to varying roughness values across a cross-section

147

Manning’s Equation: HEC-RAS computes Manning’s Equation to determine

friction losses due to the material comprising the channel

or left/right overbank. Roughness coefficients for cross-

section input are estimated using values in Appendix A

Reach Length (m): Distance, in meters, between a cross-section and the

adjacent downstream section

Shear Stress (τ) (N/m2): Shear stress is solved as part of the conservation of

momentum equation used in HEC-RAS, and is the

tractive (pulling) force of the water on the channel

bed/banks and sediments. Shear stress can be calculated

as:

𝜏 = 𝛾 �̅�𝑆�̅�

where:

𝛾 = Standard Unit Wt. of H2O

Sf = Slope of energy grade line (friction

slope)

�̅� = Avg. hydraulic radius

�̅� = 𝐴/𝑃

where:

A = Avg. wetted area

P = Avg. wetted perimeter

148

Stream Power (watts/m): The ability of a channel to do geomorphic work

(i.e. move sediment). Unit stream power is the

product of the shear stress and average velocity

per unit width of channel

ω = τ �̅�

where:

ω = unit stream power

τ = shear stress

�̅� = average velocity

Top Width (m): Top width of the wetted cross-section, in meters

Wetted Perimeter (m): The length of the perimeter of channel that is submerged

by a given discharge

149

APPENDIX B: Survey Benchmark Data

Survey Benchmark Data

Benchmark Point Northing Easting Elevation Note

SAD_BM_right

4421665.085 290215.829 334.381

1

TEMP_BM_left 4421541.771 290261.258 334.084 2

Coordinate System Data:

NAD_1983_UTM_Zone_18N

WKID: 26918 Authority: EPSG Projection: Transverse_Mercator False_Easting: 500000.0 False_Northing: 0.0

Central_Meridian: -75.0 Scale_Factor: 0.9996

Latitude_Of_Origin: 0.0 Linear Unit: Meter (1.0)

Notes: 1 - Benchmark is positioned atop the remaining right dam abutment (facing downstream),

and was surveyed by Dr. Scott Drzyzga 2 - Benchmark is temporary, and positioned atop the remaining portion of the left dam abutment (looking downstream), and was surveyed by Zachary Phillips and Emery Saylor

150

APPENDIX C: Bathymetry Survey Cross-section Endpoint Data

OBJ_ID Cross-section

Northing (m)

Easting (m)


Northing (m)

Easting (m)

1 1 4421654.68 289999.59

35 18 4421624.59 290087.40

2 1 4421644.36 289995.54

36 18 4421628.27 290087.08

3 2 4421641.75 290019.04

37 19 4421625.64 290094.19

4 2 4421650.25 290019.54

38 19 4421629.12 290094.00

5 3 4421641.47 290026.30

39 20 4421623.60 290099.89

6 3 4421650.17 290026.49

40 20 4421626.84 290099.71

7 4 4421639.21 290043.20

41 21 4421630.41 290107.87

8 4 4421648.73 290043.73

42 21 4421631.44 290103.82

9 5 4421650.62 290062.07

43 22 4421637.11 290109.57

10 5 4421653.72 290061.33

44 22 4421645.35 290106.51

11 6 4421635.75 290061.69

45 23 4421637.44 290115.07

12 6 4421640.84 290063.30

46 23 4421646.33 290114.11

13 7 4421631.36 290065.90

47 24 4421643.11 290127.98

14 7 4421634.30 290069.85

48 24 4421649.52 290125.94

15 8 4421639.19 290071.13

49 26 4421645.24 290132.43

16 8 4421643.26 290069.59

50 26 4421651.22 290130.90

17 9 4421654.43 290072.45

51 27 4421646.32 290136.23

18 9 4421650.36 290070.63

52 27 4421653.28 290135.95

19 10 4421646.74 290074.25

53 28 4421640.85 290142.34

20 10 4421648.67 290077.60

54 28 4421652.34 290145.62

21 11 4421643.43 290074.91

55 29 4421642.25 290147.96

22 11 4421645.08 290073.93

56 29 4421648.40 290150.77

23 12 4421642.43 290076.65

57 30 4421633.23 290154.95

24 12 4421645.88 290081.28

58 30 4421646.80 290164.63

25 13 4421639.11 290080.11

59 31 4421629.37 290184.70

26 13 4421645.23 290083.12

60 31 4421617.84 290175.53

27 14 4421635.66 290087.49

61 32 4421621.23 290197.13

28 14 4421643.62 290087.66

62 32 4421606.14 290186.46

29 15 4421635.31 290093.30

63 33 4421609.75 290216.15

30 15 4421644.96 290093.24

64 33 4421593.76 290209.57

31 16 4421627.20 290071.51

65 34 4421604.12 290232.56

32 16 4421629.75 290073.30

66 34 4421588.81 290231.77

33 17 4421623.73 290076.72

67 35 4421603.23 290241.09

34 17 4421626.74 290077.49

68 35 4421590.32 290242.01

151


Northing (m)

Easting (m)

OBJ_ID Cross-section Northing

(m) Easting

(m)

137 70 4421774.43 290532.67

171 98 4422021.78 290688.80

138 70 4421782.58 290526.86

172 98 4422026.84 290677.80

139 71 4421785.39 290545.30

173 111 4422208.04 290892.64

140 71 4421792.19 290540.03

174 111 4422215.46 290886.31

141 72 4421794.75 290558.87

175 112 4422249.01 290931.93

142 72 4421802.14 290553.89

176 112 4422258.54 290930.02

143 73 4421795.67 290560.25

177 115 4422255.36 291014.37

144 73 4421803.47 290555.20

178 115 4422265.10 291013.31

145 74 4421797.18 290564.89

179 116 4422265.31 291068.88

146 74 4421805.49 290558.28

180 116 4422272.82 291067.29

147 75 4421815.37 290583.62

181 117 4422268.59 291112.27

148 75 4421821.00 290577.45

182 117 4422279.91 291111.21

149 76 4421818.41 290586.45

183 119 4422288.80 291164.76

150 76 4421823.30 290580.12

184 119 4422279.17 291166.14

151 77 4421835.22 290597.09

185 120 4422292.30 291189.10

152 77 4421839.13 290586.53

186 120 4422281.92 291189.72

153 78 4421851.22 290602.57

187 121 4422308.28 291267.17

154 78 4421851.22 290590.88

188 121 4422298.73 291272.74

155 79 4421863.24 290601.76

189 122 4422316.44 291290.28

156 79 4421863.18 290591.18

190 122 4422306.06 291293.24

157 83 4421881.15 290603.22

191 123 4422341.96 291338.01

158 83 4421886.02 290596.35

192 123 4422331.15 291342.11

159 85 4421901.50 290618.42

193 125 4422364.36 291369.59

160 85 4421906.62 290608.32

194 125 4422353.26 291376.89

161 86 4421908.18 290621.57

195 126 4422369.31 291387.66

162 86 4421913.73 290612.98

196 126 4422360.40 291390.04

163 88 4421914.07 290625.81

197 127 4422397.13 291461.60

164 88 4421920.42 290617.37

198 127 4422408.53 291453.72

165 89 4421929.41 290644.75

199 128 4422439.89 291512.09

166 89 4421942.76 290636.38

200 128 4422446.77 291503.75

167 96 4421970.19 290668.15

201 129 4422468.97 291536.21

168 96 4421974.03 290657.73

202 129 4422475.67 291524.45

169 97 4422003.81 290682.71

203 130 4422500.70 291539.40

170 97 4422008.02 290671.40

204 130 4422499.31 291547.60

152

OBJ_ID Cross-section Northing

(m) Easting

(m) OBJ_ID Cross-section

Northing (m)

Easting (m)

205 131 4422530.81 291547.76

239 154 4422274.50 291146.22

206 131 4422529.54 291554.85

240 154 4422285.28 291144.63

207 132 4422680.54 291533.51

241 155 4422349.08 291368.34

208 132 4422683.52 291541.78

242 155 4422357.50 291363.89

209 133 4422752.42 291462.59

243 156 4422365.18 291370.83

210 133 4422758.69 291470.83

244 156 4422354.11 291378.16

211 134 4422777.55 291438.51

245 157 4422793.16 291426.61

212 134 4422781.52 291445.66

246 157 4422797.44 291432.36

213 136 4422505.52 291561.63

247 158 4422776.08 291439.31

214 136 4422515.80 291555.44

248 158 4422780.05 291446.46

215 138 4422537.93 291572.87

249 159 4422099.63 290739.39

216 138 4422535.61 291579.49

250 159 4422106.96 290734.12

217 141 4422650.17 291627.06

251 160 4422150.05 290804.94

218 141 4422646.60 291634.60

252 160 4422156.19 290800.14

219 142 4422696.94 291629.09

220 142 4422693.59 291635.04

221 143 4422735.60 291606.05

222 143 4422740.45 291611.74

223 144 4422776.56 291611.74

224 144 4422775.37 291619.68

225 145 4422805.54 291603.80

226 145 4422810.89 291610.27

227 146 4422861.71 291570.16

228 146 4422865.96 291576.19

229 147 4422865.71 291567.93

230 147 4422868.83 291573.83

231 148 4422878.50 291564.65

232 148 4422878.50 291575.55

233 149 4422888.51 291565.33

234 149 4422888.15 291574.46

235 150 4422800.99 291421.85

236 150 4422805.07 291430.17

237 152 4422572.11 291541.55

238 152 4422571.47 291550.37

153

APPENDIX D: Manning’s Roughness Values

Manning's 'n' Values (adapted from HEC-RAS Hydraulic Reference Manual)

Type of Channel and Description Manning's 'n' Value

A. Natural Streams

1. Main Channels Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Clean, straight, full, no rifts or deep pools 0.025 0.03 0.033

b. Same as above, but more stones and weeds 0.03 0.035 0.04

c. Clean, winding, some pools and shoals 0.033 0.04 0.045

d. Same as above, but some weeds and stones 0.035 0.045 0.05

e. Same as above, lower stages, more ineffective slopes and sections

0.04 0.048 0.055

f. Same as "d" but more stones 0.045 0.05 0.06 g. Sluggish reaches, weedy. deep pools 0.05 0.07 0.08 h. Very weedy reaches, deep pools, or floodways with heavy stands of timber and brush

0.07 0.1 0.15

2. Flood Plains Min. 'n' Value Normal 'n' Value Max. 'n' Value

Pasture no brush

a. Short grass 0.025 0.03 0.035

b. High grass 0.03 0.035 0.05

Cultivated areas

a. No crop 0.2 0.03 0.035

b. Mature row crops 0.025 0.035 0.045

c. Mature field crops 0.03 0.04 0.05

Brush

a. Scattered brush, heavy weeds 0.035 0.05 0.07

b. Light brush and trees, in winter 0.035 0.05 0.06

c. Light brush and trees, in summer 0.04 0.06 0.08

d. Medium to dense brush, in winter 0.045 0.07 0.11

e. Medium to dense brush, in summer 0.07 0.1 0.16

Trees

a. Cleared land with tree stumps, no sprouts 0.03 0.04 0.05

b. Same as above, but heavy sprouts 0.05 0.06 0.08

c. Heavy stand of timber, few down trees, little undergrowth, flow below branches

0.08 0.1 0.12

d. Same as above, but with flow into branches 0.1 0.12 0.16

e. Dense willows, summer, straight 0.11 0.15 0.2

3. Mountain Streams, no vegetation in channel, banks usually steep, with trees and brush on banks submerged

Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Bottom: gravels, cobbles, and few boulders 0.03 0.04 0.05

b. Bottom: cobbles with large boulders 0.04 0.05 0.07

154

B. Lined or Built-Up Channels

1. Concrete Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Trowel finish 0.011 0.013 0.015

b. Float Finish 0.013 0.015 0.016

c. Finished, with gravel bottom 0.015 0.017 0.02 d. Unfinished 0.014 0.017 0.02

e. Gunite, good section 0.016 0.019 0.023

f. Gunite, wavy section 0.018 0.022 0.025

g. On good excavated rock 0.017 0.02

h. On irregular excavated rock 0.022 0.027

2. Concrete bottom float finished with sides of: Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Dressed stone in mortar 0.015 0.017 0.02

b. Random stone in mortar 0.017 0.02 0.024

c. Cement rubble masonry, plastered 0.016 0.02 0.024

d. Cement rubble masonry 0.02 0.025 0.03

e. Dry rubble on riprap 0.02 0.03 0.035

3. Gravel bottom with sides of: Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Formed concrete 0.017 0.02 0.025

b. Random stone in mortar 0.02 0.023 0.026

c. Dry rubble or riprap 0.023 0.033 0.036

4. Brick Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Glazed 0.011 0.013 0.015

b. In cement mortar 0.012 0.015 0.018

5. Metal Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Smooth steel surfaces b. Corrugated metal 0.011 0.012 0.014

6. Asphalt Min. 'n' Value Normal 'n' Value Max. 'n' Value

a. Smooth 0.013 0.013

b. Rough 0.016 0.016

** (from USACE, 2010)

155

APPENDIX E: Cross-sectional Data

**Cross-section numbering starts at the downstream section and proceeds upstream to the Birch

Run/Conococheague Creek confluence**

Cross Section 22

Downstream Reach Lengths

Left Overbank Channel Right Overbank

0 0 0

Manning's Roughness (n)


0.1 0.04 0.1

Cross Section 23



12.34 6.61 3.87



0.1 0.04 0.1

*Gray portion of elevation profile is the stream channel

312

314

316

318

320

322

324

326

328

0 20 40 60 80 100 120

Elev

atio

n (

m)

Lateral Distance (R to L looking upstream) (m)

Cross-section 22 Elevation Profile

310

315

320

325

330

335

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



156

Cross Section 24



9.37 13.28 15.92



0.1 0.04 0.1

Cross Section 25



6.1 5.08 4.16



0.1 0.04 0.1


312314316318320322324326328330332334

0 10 20 30 40 50 60 70 80

Elev

atio

n (

m)


Crosss-section 24 Elevation Profile

310

315

320

325

330

335

0 20 40 60 80 100 120

Elev

atio

n (

m)



157

Cross Section 26



6.58 4.73 3



0.1 0.04 0.1

Cross Section 27



11.72 8.54 6.01



0.1 0.04 0.1


310

315

320

325

330

335

340

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



310

315

320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



158

Cross Section 28: Riprap Downstream Extent



8.71 5.75 3.48



0.03 0.033 0.03

Cross Section 29: Riprap



13.67 12.02 9.57



0.03 0.033 0.03


310

315

320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



310

315

320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



159




26.66 26.26 26.17



0.03 0.033 0.03




14.62 15.34 15.90



0.03 0.033 0.03


310

315

320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



310

315

320

325

330

335

0 50 100 150 200 250

Elev

atio

n (

m)



160




19.56 24.76 30.85



0.03 0.033 0.03




14.02 19.8 30.74



0.03 0.033 0.03


314

316

318

320

322

324

326

328

330

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



310

315

320

325

330

335

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



161




7.56 9.32 12.77



0.03 0.033 0.03




5.22 6.74 8.12



0.03 0.033 0.03

* Gray portion of elevation profile is the stream channel

310

315

320

325

330

335

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



310

315

320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n



162

Cross Section 36: Riprap upstream extent



28.23 30.3 31.61



0.03 0.033 0.03

Cross Section 37



3.48 10.43 22.14



0.1 0.04 0.03


310

315

320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



316

316.5

317

317.5

318

318.5

319

319.5

0 10 20 30 40 50 60

Elev

atio

n (

m)



163

Cross Section 38



18.99 20.88 24.09



0.1 0.04 0.03

Cross Section 39



5.22 9.41 15.5



0.1 0.04 0.1


315

320

325

330

335

340

0 10 20 30 40 50 60 70 80 90

Elev

atio

n (

m)



310

315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



164

Cross Section 40



9.65 14.37 16.01



0.1 0.04 0.1

Cross Section 41



11.05 13.65 16.94



0.1 0.04 0.1


315

320

325

330

335

340

345

0 20 40 60 80 100 120

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



165

Cross Section 42



26.7 34.66 37.65



0.1 0.04 0.1

Cross Section 43



14.51 11.95 8.8



0.1 0.04 0.1


315

320

325

330

335

340

345

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



316

318

320

322

324

326

328

330

332

334

336

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



166

Cross Section 44



8.37 6.91 4.83



0.1 0.04 0.1

Cross Section 45



16.55 15.87 15.47



0.1 0.04 0.1


315

320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



167

Cross Section 46



16.75 12.91 8.07



0.1 0.04 0.1

Cross Section 47



9.08 5.79 4.44



0.1 0.04 0.1


315

320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



315

320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



168

Cross Section 48



15.44 14.17 14.49



0.1 0.04 0.1

Cross Section 55



19.24 19.71 19.78



0.1 0.04 0.1


315

320

325

330

335

340

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



315

320

325

330

335

340

0 50 100 150 200 250 300

Elev

atio

n (

m)



169

Cross Section 56



11.28 11.68 14.54



0.1 0.04 0.1

Cross Section 57



11.06 15.89 16.55



0.1 0.04 0.1


315

320

325

330

335

340

0 50 100 150 200 250 300

Elev

atio

n (

m)



316318320322324326328330332334336338

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



170

Cross Section 58



8.48 9.11 11.54



0.1 0.04 0.1

Cross Section 59



18.22 19.72 20.2



0.1 0.04 0.1


315

320

325

330

335

340

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



171

Cross Section 60



6.61 18.498 24.57



0.1 0.04 0.1

Cross Section 61



25.49 9.96 3.34



0.1 0.04 0.1


319.2

319.4

319.6

319.8

320

320.2

320.4

320.6

0 5 10 15 20 25 30 35 40

Elev

atio

n (

m)



318320322324326328330332334336338340

0 50 100 150 200 250

Elev

atio

n (

m)



172

Cross Section 62



29.92 20.86 15.26



0.1 0.04 0.1

Cross Section 63



2.98 2.82 3.37



0.1 0.04 0.1


315

320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



318

320

322

324

326

328

330

332

334

336

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



173

Cross Section 64



3.12 3.34 2.73



0.1 0.04 0.1

Cross Section 65



4.34 7.89 11.38



0.1 0.04 0.1


318

320

322

324

326

328

330

332

334

336

338

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



174

Cross Section 66



6.21 8.04 11.08



0.1 0.04 0.1

Cross Section 67



4.14 4.27 4.11



0.1 0.04 0.1


318

320

322

324

326

328

330

332

334

336

338

0 50 100 150 200 250 300

Elev

atio

n (

m)



315

320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



175

Cross Section 68



7.87 6.5 4.88



0.1 0.04 0.1

Cross Section 69



5.6 4.58 4.28



0.1 0.04 0.1


315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



176

Cross Section 70



16.16 16.52 16.98



0.1 0.04 0.1

Cross Section 71



19.05 16.68 16.11



0.1 0.04 0.1


315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



177

Cross Section 72



2.1 1.74 1.9



0.1 0.04 0.1

Cross Section 73



2.49 4.33 4.96



0.1 0.04 0.1


315

320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



178

Cross Section 74



23.27 25.43 30.34



0.1 0.04 0.1

Cross Section 75



2.09 3.76 4.66



0.1 0.04 0.1


315

320

325

330

335

340

345

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



315

320

325

330

335

340

345

0 20 40 60 80 100 120

Elev

atio

n (

m)



179

Cross Section 76



14.53 18.82 26.24



0.1 0.04 0.1

Cross Section 77



7.65 15.14 25.77



0.1 0.04 0.1


320

322

324

326

328

330

332

334

336

338

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



321

321.5

322

322.5

323

323.5

324

324.5

325

0 20 40 60 80 100 120

Elev

atio

n (

m)



180

Cross Section 78



11.57 12.05 11.58



0.1 0.04 0.1

Cross Section 79



19.1 8.44 3.33



0.05 0.04 0.05


320.5

321

321.5

322

322.5

323

323.5

324

324.5

0 10 20 30 40 50 60 70 80 90

Elev

atio

n (

m)



320.5

321

321.5

322

322.5

323

323.5

324

324.5

325

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



181

Cross Section 80



4.87 4.5 5.02



0.05 0.04 0.05

Cross Section 81



4.87 2.58 7.78



0.05 0.04 0.05


321

322

323

324

325

326

327

0 20 40 60 80 100 120

Elev

atio

n (

m)



320

322

324

326

328

330

332

334

336

338

0 50 100 150 200 250

Elev

atio

n (

m)



182

Cross Section 82



12.61 4.34 2.6



0.05 0.04 0.05

Cross Section 83: Bank Vane 1



2.57 3.86 4.17



0.05 0.04 0.05


320

325

330

335

340

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



321

321.5

322

322.5

323

323.5

324

324.5

325

0 20 40 60 80 100 120

Elev

atio

n (

m)



183




2.17 3.09 4.47



0.05 0.04 0.05




6.51 6 5.46



0.05 0.04 0.05


320

322

324

326

328

330

332

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



184

Cross Section 86



10.37 11.62 10.87



0.05 0.04 0.05

Cross Section 87



9.11 7.85 5.54



0.05 0.04 0.05


320

322

324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



320

325

330

335

340

0 50 100 150 200 250

Elev

atio

n (

m)



185




4.2 2.91 2.38



0.05 0.04 0.05

Cross Section 89



5.43 4.56 4.18



0.05 0.04 0.05


320322324326328330332334336338340342

0 50 100 150 200 250

Elev

atio

n (

m)



320

325

330

335

340

345

0 50 100 150 200 250

Elev

atio

n (

m)



186

Cross Section 90



35.72 26.69 18.67



0.05 0.04 0.05




2.85 5.51 7.87



0.05 0.04 0.05


321

322

323

324

325

326

327

328

329

0 20 40 60 80 100 120

Elev

atio

n (

m)



320

322

324

326

328

330

332

334

336

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



187




2.27 2.31 3.18



0.05 0.04 0.05




2.57 3.18 4.25



0.05 0.04 0.05


320

322

324

326

328

330

332

334

336

338

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



320

322

324

326

328

330

332

334

336

338

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



188

Cross Section 94: Cross Vane 1



4.43 7.08 9.84



0.05 0.04 0.05




1.22 1.23 1.39



0.05 0.04 0.05


320

322

324

326

328

330

332

334

336

338

340

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



320322324326328330332334336338340

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



189




1.36 1.64 1.86



0.05 0.04 0.05




1.1 1.78 2.69



0.05 0.04 0.05


320322324326328330332334336338340

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



320322324326328330332334336338340

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



190




3.13 4.03 5.51



0.05 0.04 0.05

Cross Section 99



9.78 16.91 23.29



0.05 0.04 0.05


320

322

324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



320

325

330

335

340

345

0 50 100 150 200 250 300

Elev

atio

n (

m)



191

Cross Section 100



37.79 36.82 35.82



0.05 0.04 0.035

Cross Section 101



20.06 19.04 16.97



0.05 0.04 0.035


322324326328330332334336338340

0 50 100 150 200 250 300

Elev

atio

n (

m)



322

324

326

328

330

332

334

336

338

340

0 50 100 150 200 250 300

Elev

atio

n (

m)



192




59.86 59.69 58.49



0.035 0.04 0.035




42.63 36.41 23.97



0.035 0.04 0.035


322

324

326

328

330

332

334

336

338

340

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



322

324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



193




41.25 41.08 40.59



0.035 0.04 0.035




1.26 1.18 1.25



0.035 0.04 0.035


324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



194




1.92 1.92 1.89



0.035 0.04 0.035




1.86 1.97 2.06



0.035 0.04 0.035


324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



195




2.02 2.08 2.14



0.035 0.04 0.035

Cross Section 109



33.56 34.64 35.84



0.035 0.04 0.035


324

326

328

330

332

334

336

338

340

0 50 100 150 200 250

Elev

atio

n (

m)



324326328330332334336338340342344

0 50 100 150 200 250 300

Elev

atio

n (

m)



196

Cross Section 110: Downstream of Perpendicular Cross Vane



46.18 42.53 31.04



0.035 0.04 0.035

Cross Section 111: Perpendicular Cross Vane



2.65 2.69 2.85



0.035 0.04 0.035


324326328330332334336338340342344

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



324326328330332334336338340342344

0 50 100 150 200 250

Elev

atio

n (

m)



197

Cross Section 112: Upstream of Perpendicular Cross Vane



1.14 1.18 1.48



0.035 0.04 0.035

Cross Section 113



41 44.61 49.24



0.035 0.04 0.035


324

326

328

330

332

334

336

338

340

342

344

0 50 100 150 200 250

Elev

atio

n (

m)



326

328

330

332

334

336

338

340

342

344

0 50 100 150 200 250

Elev

atio

n (

m)



198

Cross Section 114



14.66 15.37 17.79



0.035 0.04 0.035




9.84 11.37 14.08



0.035 0.04 0.035


326

328

330

332

334

336

338

340

342

344

0 50 100 150 200 250

Elev

atio

n (

m)



326

328

330

332

334

336

338

340

342

344

0 50 100 150 200 250

Elev

atio

n (

m)



199




1.4 1.41 2.01



0.035 0.04 0.035




1.4 1.36 1.65



0.035 0.04 0.035


326

328

330

332

334

336

338

340

342

344

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



326

328

330

332

334

336

338

340

342

344

0 20 40 60 80 100 120 140 160

Elev

atio

n (

m)



200




1.75 1.45 1.47



0.035 0.04 0.035




1.92 2.05 2.33



0.035 0.04 0.035


326328330332334336338340342344346

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



325

330

335

340

345

0 20 40 60 80 100 120

Elev

atio

n (

m)



201

Cross Section 120



1.92 42.44 25.76



0.035 0.04 0.035




49.7 48.24 46.58



0.035 0.04 0.035


325

330

335

340

345

350

0 20 40 60 80 100 120

Elev

atio

n (

m)



325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



202




3.12 3.2 3.4



0.035 0.04 0.035




3.39 3.26 3.19



0.035 0.04 0.035


325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



326328330332334336338340342344346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



203




6.43 6.27 6.32



0.035 0.04 0.035




4.18 4.38 4.44



0.035 0.04 0.035


326328330332334336338340342344346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



326328330332334336338340342344346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



204

Cross Section 126



17.43 17.13 17.94



0.035 0.04 0.035




33.47 34.6 34.49



0.035 0.04 0.035


326

328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



205




2.23 2.28 2.19



0.035 0.04 0.035




1.48 1.44 1.54



0.035 0.04 0.035


325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328330332334336338340342344346348350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



206




1.31 1.5 1.32



0.035 0.04 0.035

Cross Section 131



1.34 1.46 1.35



0.035 0.04 0.035


328330332334336338340342344346348350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

344

346

348

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



207

Cross Section 132


Left Overbank

Channel Right

Overbank

12.63 14.15 16.14


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035




27.34 23.76 18.37



0.035 0.04 0.035


325

330

335

340

345

350

355

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



208




2.1 2.04 2.037



0.035 0.04 0.035




1.498 1.43 2



0.035 0.04 0.035


328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



209




1.66 1.75 1.84



0.035 0.04 0.035

Cross Section 137



1.82 1.95 1.93



0.035 0.04 0.035


328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



210

Cross Section 138



10.53 13.25 14.79



0.035 0.04 0.035




19.49 19.44 22.23



0.035 0.04 0.035


328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

344

346

348

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



211




3.917 4.01 4.08



0.035 0.04 0.035

Cross Section 142


Left Overbank

Channel Right

Overbank

10.15 9.91 10.03


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


328

330

332

334

336

338

340

342

344

346

348

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

344

346

348

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



212



Left Overbank

Channel Right

Overbank

7.26 8.21 8.54


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035



Left Overbank

Channel Right

Overbank

1.72 1.706 1.87


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328330332334336338340342344346348350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



213



Left Overbank

Channel Right

Overbank

1.82 1.74 1.73


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035



Left Overbank

Channel Right

Overbank

1.93 1.93 1.92


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


328330332334336338340342344346348350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328330332334336338340342344346348350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



214



Left Overbank

Channel Right

Overbank

1.93 1.98 2.08


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035

Cross Section 148


Left Overbank

Channel Right

Overbank

5.27 4.54 4.24


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


328330332334336338340342344346348350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



215



Left Overbank

Channel Right

Overbank

4.06 4.66 5.27


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035



Left Overbank

Channel Right

Overbank

1.44 1.54 1.59


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



216



Left Overbank

Channel Right

Overbank

2.18 2.07 2.23


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035



Left Overbank

Channel Right

Overbank

1.83 2.03 1.94


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


325

330

335

340

345

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



328

330

332

334

336

338

340

342

344

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



217



Left Overbank

Channel Right

Overbank

1.97 2.05 2.19


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035

Cross Section 154


Left Overbank

Channel Right

Overbank

16.28 11.87 9.02


Left Overbank

Channel Right

Overbank

0.035 0.04 0.035


328

330

332

334

336

338

340

342

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



325

330

335

340

345

350

355

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



218

Cross Section 155


Left Overbank

Channel Right

Overbank

16.28 11.87 9.02


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 156


Left Overbank

Channel Right

Overbank

33.54 22.38 18.7


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


330

332

334

336

338

340

342

344

346

348

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



330

332

334

336

338

340

342

344

346

348

350

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



219

Cross Section 157


Left Overbank

Channel Right

Overbank

52.92 54.54 55.27


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 158


Left Overbank

Channel Right

Overbank

22.34 30.96 34.39


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


330

335

340

345

350

355

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



332

334

336

338

340

342

344

346

348

350

352

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



220

Cross Section 159


Left Overbank

Channel Right

Overbank

6.87 9.06 10.83


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 160


Left Overbank

Channel Right

Overbank

1.24 1.51 1.86


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


330

335

340

345

350

355

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



330

335

340

345

350

355

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



221

Cross Section 161


Left Overbank

Channel Right

Overbank

15.29 15.38 13.31


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 162


Left Overbank

Channel Right

Overbank

79.1 86 84.57


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


330

335

340

345

350

355

360

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



334336338340342344346348350352354356

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



222

Cross Section 163


Left Overbank

Channel Right

Overbank

46.17 61.51 69.34


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 163


Left Overbank

Channel Right

Overbank

46.17 61.51 69.34


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



336

338

340

342

344

346

348

350

352

354

356

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



223

Cross Section 164


Left Overbank

Channel Right

Overbank

31.21 38.33 40.87


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 165


Left Overbank

Channel Right

Overbank

17.25 31.42 40.41


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


335

340

345

350

355

360

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



336

338

340

342

344

346

348

350

352

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



224

Cross Section 166: Conococheague Creek Upper Reach


Left Overbank

Channel Right

Overbank

0 0 0


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

25.73 32.46 39.51


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


337.5

338

338.5

339

339.5

340

340.5

341

0 2 4 6 8 10 12 14 16 18

Elev

atio

n (

m)



338

340

342

344

346

348

350

352

354

356

0 10 20 30 40 50 60 70 80

Elev

atio

n (

m)



225



Left Overbank

Channel Right

Overbank

126.04 129.25 122.78


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

44.77 48.51 40.94


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


338340342344346348350352354356358360

0 10 20 30 40 50 60 70 80 90

Elev

atio

n (

m)



340

345

350

355

360

365

0 20 40 60 80 100 120

Elev

atio

n (

m)



226



Left Overbank

Channel Right

Overbank

22.15 71.02 78.76


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

53.37 42.37 15.25


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


341.8

342

342.2

342.4

342.6

342.8

343

343.2

343.4

343.6

0 10 20 30 40 50 60 70 80 90 100

Elev

atio

n (

m)



340

342

344

346

348

350

352

354

356

358

360

0 20 40 60 80 100 120

Elev

atio

n (

m)



227



Left Overbank

Channel Right

Overbank

18.12 35.5 64.66


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

69.16 65.5 52.73


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


343

343.5

344

344.5

345

345.5

346

346.5

0 20 40 60 80 100 120 140

Elev

atio

n (

m)



344.6

344.8

345

345.2

345.4

345.6

345.8

346

0 20 40 60 80 100 120

Elev

atio

n (

m)



228



Left Overbank

Channel Right

Overbank

5.56 4.42 3.3


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1

Cross Section 175: Conococheague Creek Upper Reach (USGS Gage 01614090)


Left Overbank

Channel Right

Overbank

29.71 10.97 6.59


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


345.2

345.3

345.4

345.5

345.6

345.7

345.8

345.9

346

346.1

346.2

0 20 40 60 80 100 120

Elev

atio

n (

m)



344

346

348

350

352

354

356

358

360

0 50 100 150 200 250

Elev

atio

n (

m)



229

Cross Section 177: Birch Run


Left Overbank

Channel Right

Overbank

0 0 0


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

34.1 41.61 42.28


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


337

338

339

340

341

342

343

344

345

346

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



338

340

342

344

346

348

350

352

354

0 20 40 60 80 100 120 140 160 180 200

Elev

atio

n (

m)



230



Left Overbank

Channel Right

Overbank

88.89 112.46 118.62


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

76.23 103.39 108.79


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


335

340

345

350

355

360

365

370

0 50 100 150 200 250

Elev

atio

n (

m)



342

344

346

348

350

352

354

356

358

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



231



Left Overbank

Channel Right

Overbank

34.81 33.13 26.59


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1



Left Overbank

Channel Right

Overbank

1.67 1.71 1.68


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


342

344

346

348

350

352

354

356

358

360

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



342

344

346

348

350

352

354

356

358

360

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



232

Cross Section 183: Birch Run Stream Gage (USGS 01614100)


Left Overbank

Channel Right

Overbank

18.61 20.22 23.87


Left Overbank

Channel Right

Overbank

0.1 0.04 0.1


342

344

346

348

350

352

354

356

358

360

362

0 20 40 60 80 100 120 140 160 180

Elev

atio

n (

m)



233

APPENDIX F: Pre-/Post-restoration HEC-RAS Modeling Results

** Flow Profiles A – E represented here by PF 1, PF 3, PF 4, PF 5, and PF 6**

Pre-restoration modeling results

River x-sect Profile

Q Total

Min Ch El

W.S. Elev E.G. Slope

Flow Vel

Flow Area

Top Width

Hydr RadII

Strea Powr

Shear Chan

(m3/s) (m) (m) (m/m) (m/s) (m2) (m) (m) (N/m s) (N/m2)

Birch Run 183 PF 1 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 3 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 4 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 5 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 6 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 182 PF 1 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 3 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 4 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 5 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 6 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 181 PF 1 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 3 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 4 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 5 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 6 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 180 PF 1 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 3 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 4 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 5 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 6 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 179 PF 1 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 3 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 4 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 5 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 6 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 178 PF 1 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 3 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 4 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 5 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 6 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 177 PF 1 0.09 337.63 337.94 0.000112 0.1 0.9 3.45 0.24 0.03 0.27

Birch Run 177 PF 3 0.09 337.63 338.24 0.00001 0.05 2.02 3.99 0.45 0 0.04

Birch Run 177 PF 4 0.09 337.63 338.44 0.000004 0.03 2.86 4.35 0.57 0 0.02

Birch Run 177 PF 5 0.09 337.63 338.59 0.000002 0.03 3.75 11.81 0.3 0 0.01

Birch Run 177 PF 6 0.09 337.63 338.65 0.000002 0.02 4.51 14.95 0.28 0 0.01

234

Conococheague Cr 175 PF 1 0.59 344.84 345.66 0.000094 0.17 3.59 4.86 0.57 0.09 0.52
















Conococheague Cr 172 PF 3 2.93 343.3 343.82 0.025888 2.02 1.45 3.41 0.36 183 90.49





Conococheague Cr 171 PF 3 2.93 342.54 343.02 0.020754 1.67 2 9.27 0.21 107.26 64.24







Conococheague Cr 170 PF 5 8.6 341.95 343.02 0.002356 0.93 16.31 41 0.39 14.6 15.62




















235







































Conococheague Cr 158 PF 3 3.02 333.58 334 0.013842 1.16 2.61 10.46 0.24 38.85 33.54









236









































Conococheague Cr 131 PF 1 0.69 329.31 329.51 0.034919 1 0.69 7.01 0.1 33.63 33.75








237
















Conococheague Cr 113 PF 5 8.69 326.77 327.63 0.009257 1.72 5.39 12.1 0.43 94.73 55
































238

















































239















Conococheague Cr 72 PF 4 5.96 319.89 320.61 0.00907 1.49 4 7.32 0.49 65.54 44

































240

















































241
















































242

















































243
















































244

245

Post-restoration modeling results

River x-sect

Flow Pro

Q Tot.

Min Ch El

W.S. Elev

E.G. Slope

Vel Chnl

Flow Area

Top Width

Hydr Radii

Pow. Chan

Shear Chan

m3/s m m m/m m/s M2 m m N/m s N/m2

Birch Run 183 PF 1 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 3 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 4 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 5 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 183 PF 6 0.09 343.95 344.54 0.000005 0.03 2.79 4.88 0.48 0 0.02

Birch Run 182 PF 1 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 3 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 4 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 5 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 182 PF 6 0.09 342.97 344.54 0 0.01 7.03 5.37 0.89 0 0

Birch Run 181 PF 1 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 3 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 4 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 5 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 181 PF 6 0.09 344.43 344.52 0.016846 0.5 0.19 3.07 0.06 4.99 9.99

Birch Run 180 PF 1 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 3 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 4 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 5 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 180 PF 6 0.09 343.56 343.67 0.042285 0.71 0.13 2.57 0.05 14.95 21.15

Birch Run 179 PF 1 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 3 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 4 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 5 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 179 PF 6 0.09 341.17 341.27 0.011762 0.5 0.19 2.33 0.08 4.56 9.13

Birch Run 178 PF 1 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 3 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 4 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 5 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 178 PF 6 0.09 338.87 339.01 0.04058 0.83 0.11 1.62 0.07 22.4 26.84

Birch Run 177 PF 1 0.09 337.63 337.94 0.000112 0.1 0.9 3.45 0.24 0.03 0.27

Birch Run 177 PF 3 0.09 337.63 338.24 0.00001 0.05 2.02 3.99 0.45 0 0.04

Birch Run 177 PF 4 0.09 337.63 338.44 0.000004 0.03 2.86 4.35 0.57 0 0.02

Birch Run 177 PF 5 0.09 337.63 338.59 0.000002 0.03 3.75 11.81 0.3 0 0.01

Birch Run 177 PF 6 0.09 337.63 338.65 0.000002 0.02 4.51 14.95 0.28 0 0.01










246
















































247

















































248
















































249

















































250
















































251

















































252










Conococheague Cr 114 PF 5 8.69 327.02 327.82 0.008449 1.57 5.61 11.18 0.48 74 47






































253

















































254
















































255

















































256





























Conococheague Cr 72 PF 4 5.96 319.89 320.61 0.00907 1.49 4 7.32 0.49 65.54 44



















257

















































258
















































259

















































260
















































261















262

APPENDIX G: Wolman Pebble Count Data

**Data presented here was collected in the summers of 2009, 2011, and 2013 by the Geography 440: Field Methods in Geography Course. Sampling locations are downstream of Reach 1, upstream

of Reach 5 on Birch Run and Conococheague Creek, and within Reach 4 and 3 within the former reservoir. The data uses site labels such as Alpha, Bravo, Echo, Delta, and Gamma, for which

locations in relation to this study are noted in each table **

ALPHA (Reach 3)

2009

2011

2013

Class Size (mm) % Cum. %

% Cum. %

% Cum. %

sand < 2 6.06 6.06 0.00 0.00 16.58 16.60

v. fine gravel 2-4 0.00 6.06 1.00 1.00 1.04 17.62

fine gravel 4-6 1.01 7.07 1.00 2.00 1.55 19.17

fine gravel 6-8 2.02 9.09 2.00 4.00 0.52 19.69

med gravel 8-11 0.00 9.09 4.00 8.00 2.59 22.28

med gravel 11-16 2.02 11.11 3.00 11.00 2.59 24.87

coarse gravel 16-22 3.03 14.14 6.00 17.00 2.07 26.94

coarse gravel 22-32 9.09 23.23 18.00 35.00 2.59 29.53

v. coarse gravel 32-45 11.11 34.34 19.00 54.00 6.74 36.27

very coarse gravel 45-64 14.14 48.48 16.00 70.00 8.29 44.56

small cobble 64-90 23.23 71.72 16.00 86.00 16.06 60.62

medium cobble 90-128 11.11 82.83 10.00 96.00 19.17 79.79

large cobble 128-180 8.08 90.91 3.00 99.00 6.74 86.53

very large cobble 180-256 8.08 98.99 1.00 100.00 7.77 94.30

small boulder 256-572 1.01 100.00 0.00 100.00 5.70 100.00

medium boulder 572-1024 0.00 100.00 0.00 100.00 0.00 100.00

large boulder 1024-2048 0.00 100.00 0.00 100.00 0.00 100.00

very large boulder 2048-4096 0.00 100.00 0.00 100.00 0.00 100.00

263

BRAVO (Reach 4)

2009

2011

2013


% Cum. %

% Cum. %

sand < 2 1.96 1.96 0.00 0.00 1.34 1.34

very fine gravel 2-4 0.00 1.96 0.00 0.00 0.00 1.34

fine gravel 4-6 1.96 3.92 0.00 0.00 0.67 2.01

fine gravel 6-8 3.92 7.84 0.00 0.00 0.00 2.01

med gravel 8-11 5.88 13.73 0.00 0.00 1.34 3.35

med gravel 11-16 6.86 20.59 0.00 0.00 0.67 4.02

coarse gravel 16-22 5.88 26.47 0.85 0.85 2.68 6.71

coarse gravel 22-32 2.94 29.41 0.00 0.85 0.67 7.38



small cobble 64-90 12.75 50.00 10.25 17.09 6.04 21.47

medium cobble 90-128 8.82 58.82 35.05 52.14 5.37 26.84

large cobble 128-180 14.71 73.53 23.07 75.21 15.44 42.28

very large cobble 180-256 14.71 88.24 14.53 89.74 15.44 57.72

small boulder 256-572 7.84 96.08 10.26 100.00 23.49 81.21

medium boulder 572-1024 3.92 100.00 0.00 100.00 13.42 94.63

large boulder 1024-2048 0.00 100.00 0.00 100.00 5.37 100.00

very large boulder 2048-4096 0.00 100.00 0.00 100.00 0.00 100.00

ECHO (Downstream of Reach 1)

2013


sand < 2 21.50 21.50

very fine gravel 2-4 3.74 25.24

fine gravel 4-6 4.67 29.91

fine gravel 6-8 1.87 31.78

med gravel 8-11 2.80 34.58

med gravel 11-16 6.54 41.13

coarse gravel 16-22 1.87 43.00


very coarse gravel 32-45 2.80 54.21


small cobble 64-90 0.93 55.14

medium cobble 90-128 3.74 58.88

large cobble 128-180 7.48 66.36

very large cobble 180-256 7.48 73.84

small boulder 256-572 22.43 96.27

medium boulder 572-1024 2.80 99.07

large boulder 1024-2048 0.93 100.00

264

Foxtrot (Upstream of Conococheague Creek Stream gage)

2013


sand < 2 35.04 35.04


fine gravel 4-6 0.73 36.50

fine gravel 6-8 2.92 39.42

med gravel 8-11 0.00 39.42

med gravel 11-16 2.92 42.34





small cobble 64-90 2.92 65.70

medium cobble 90-128 2.92 68.62

large cobble 128-180 6.57 75.19


small boulder 256-572 8.03 89.05

medium boulder 572-1024 5.84 94.89

large boulder 1024-2048 5.11 100.00

very large boulder 2048-4096 0.00 100.00

Golf (Upstream of Birch Run Stream gage)

2013


sand < 2 46.03 46.03


fine gravel 4-6 2.38 48.41

fine gravel 6-8 4.76 53.17

med gravel 8-11 7.14 60.32

med gravel 11-16 8.73 69.05

coarse gravel 16-22 13.49 82.54




small cobble 64-90 1.59 92.06

medium cobble 90-128 0.00 92.06

large cobble 128-180 1.59 93.65


small boulder 256-572 2.38 97.62

medium boulder 572-1024 2.38 100.00

Documents

HYDRAULIC INVESTIGATION OF STREAM RESTORATION … · 2017-11-17 · 1 CHAPTER 1: INTRODUCTION Introduction The damming of U.S. streams and rivers has occurred since colonial times