Hydrologic Modelling to Support Wingham and Area Flood ...€¦ · flood plain mapping across North America. Outputs from the developed hydrologic model were applied as boundary conditions

Hydrologic Modelling toSupport Wingham and AreaFlood Plain MappingFINAL REPORT

Prepared for

Maitland Valley Conservation Authority1093 Marietta StWroxeter, ON N0G 2X0

March 12, 2020Project No. P2019-391

Prepared by

GeoProcess Research Associates Inc.133 King Street WestPO Box 65506 DUNDASDundas, ON L9H 6Y6

KNOWLEDGE RESEARCH CONSULTING

MAITLAND VALLEY CONSERVATION AUTHORITYHYDROLOGIC MODELLING TO SUPPORT WINGHAM AND AREA FLOOD PLAIN MAPPING MARCH 2020

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Table of ContentsList of Tables ............................................................................................................................................................................................iiList of Figures ......................................................................................................................................................................................... iiiList of Maps ............................................................................................................................................................................................ iii1. Introduction ....................................................................................................................................................................................... 12. Hydrologic Setting .......................................................................................................................................................................... 1

2.1. Land Cover ................................................................................................................................................................................. 22.2. Soil Classification ..................................................................................................................................................................... 22.3. Streamflow Monitoring Network ...................................................................................................................................... 32.4. Rainfall Network ...................................................................................................................................................................... 3

3. Model Structure ............................................................................................................................................................................... 43.1. Model Code ............................................................................................................................................................................... 43.2. Calibration Catchments......................................................................................................................................................... 53.3. Spatial Discretization ............................................................................................................................................................. 53.4. Process Representation......................................................................................................................................................... 83.5. Parameterization...................................................................................................................................................................... 83.6. Climate Forcing ...................................................................................................................................................................... 11

4. Calibration and Validation ......................................................................................................................................................... 125. Hurricane Hazel Regional Regulatory Event ....................................................................................................................... 156. Model Files and Supporting Documentation ..................................................................................................................... 17

6.1. Limitations on Future Use .................................................................................................................................................. 177. Closing ............................................................................................................................................................................................... 188. References ........................................................................................................................................................................................ 19Maps......................................................................................................................................................................................................... 21

List of Tables

Table 1: Properties of ECCC stream gauge stations within the hydrologic study area. ............................................. 3Table 2: Properties of rainfall gauges from MVCA-DSS database employed in this study. ..................................... 4Table 3: Selected streamflow gauges for model calibration and validation. ................................................................. 5Table 4: Hydrologic model inspection points for subbasin delineation. ......................................................................... 6Table 5: Spatial properties of hydrologic basins included within the HEC-HMS model. .......................................... 6Table 6: Simulated reach properties. ............................................................................................................................................. 7



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Table 7: Hydrologic methods selected in HEC-HMS with initial values. .......................................................................... 8Table 8: SOLRIS land cover parameter lookup values. ........................................................................................................... 9Table 9: Soil texture parameter lookup values. ....................................................................................................................... 10Table 10: Initial basin parameters calculated from spatially distributed soil and land cover properties. ......... 10Table 11: Calculated initial basin estimates of Time of Concentration. ......................................................................... 11Table 12: Meteorological interpolation zones. ........................................................................................................................ 11Table 13: Calibration/validation simulation specifications and calibration statistics. ............................................... 12Table 14: 48-Hour Hurricane Hazel hyetograph (MTO, 1997). .......................................................................................... 15Table 15: Model basin reduction factors and total Hurricane Hazel 48-hour storm depths. ................................ 16Table 16: Contents of ‘20200218 - HEC HMS - Maitland River Model & Data (GeoProcess).zip’. ...................... 17

List of Figures

Figure 1: Upper Maitland HEC-HMS model spatial structure. ............................................................................................. 7Figure 2: Simulated vs. observed streamflow during the June 2017 flood event (calibration scenario 1). ...... 13Figure 3: Simulated vs. observed streamflow during the June 2015 flood event (calibration scenario 2). ...... 14Figure 4: Simulated vs. observed streamflow during the Sept 2008 flood event (validation scenario). ........... 14Figure 5: Simulated regulatory flood flows at model inspection points. ...................................................................... 16

List of Maps

Map 1: Floodplain study area intersecting the Maitland River and the community of Wingham. ..................... 22Map 2: Hydrologic study area and model boundary. ........................................................................................................... 23Map 3: Spatial distribution of land cover across the model area (from SOLRIS v2.0 MNRF (2015)). ................. 24Map 4: Spatial distribution of surface ('A' Horizon) soil texture across the model area (OMNRF, 2003). ........ 25Map 5: Active and historical ECCC stream gauges within the model boundary. ....................................................... 26Map 6: Rain gauges operated by MCVA proximal to the model boundary. ............................................................... 27Map 7: HEC-RAS model boundary with planned hydrologic model inspection points. ......................................... 28Map 8: Delineated model subbasins relative to the HEC-RAS model boundary. ...................................................... 29Map 9: Delineated model subbasins. .......................................................................................................................................... 30Map 10: Spatial distribution of interception storage derived from SOLRIS land cover mapping. ...................... 31Map 11: Spatial distribution of runoff coefficients derived from SOLRIS land cover mapping............................ 32Map 12: Spatial distribution of imperviousness derived from SOLRIS land cover mapping. ................................ 33Map 13: Spatial distribution of rooting (soil) depth derived from SOLRIS land cover mapping. ........................ 34Map 14: Spatial distribution of wilting point derived from OMAFRA soil texture mapping. ................................ 35Map 15: Spatial distribution of porosity derived from OMAFRA soil texture mapping. ......................................... 36Map 16: Spatial distribution of soil moisture storage derived from SOLRIS land coverage and OMAFRA soiltexture mapping. ................................................................................................................................................................................. 37Map 17: Meteorological interpolation zones relative to the model subbasins and boundary. ........................... 38



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1. Introduction

GeoProcess Research Associates (GeoProcess) has been retained by the Maitland ValleyConservation Authority (MVCA) to update the floodplain mapping for the Maitland River andits tributaries in the area around the community of Wingham. Within the study area, theMaitland River confluences with two tributaries: the Middle Maitland River and the Little

Maitland River (shown on Map 1). These catchments drain an area 1650 km² upstream of the community(Map 2) before draining into Lake Huron at the Town of Goderich via the Lower Maitland River. The Townof Wingham is one of the larger communities within Huron County and is an important hub for emergencyservices, including fire, paramedic and hospital (with an emergency room). As a result, characterizing theflood hazards in the area is not only important for the Town but also for the surrounding communities.

To support the hydraulic modelling efforts at Wingham, GeoProcess has developed and calibrated a rainfall-runoff model of the Maitland River watershed upstream of Wingham. The model was developed to provideestimates of streamflow through the community under the regional regulatory flood flows. The regulatoryflood within the MVCA jurisdiction is the larger of the Hurricane Hazel storm or the 100-year flood (O.Reg.164/06). As the Hurricane Hazel flows can not be determined from observations (via frequency analysis), acomputational rainfall-runoff analysis is required. Additionally, the advanced 2D nature of the hydraulicmodelling undertaken to characterize the flood response through Wingham requires transient inputs toestimate the inflow of water through the system under storm conditions.

To meet the requirements of this study, the US Army Corps of Engineers (USACE) model code HEC-HMS(Hydrologic Model System version 4.3) was employed. The HEC-HMS model was developed by the U.S. ArmyCorps of Engineers as a replacement for the HEC-1 model code recommended for use in Ontario (OMNR,2002). HEC-HMS has been widely employed in Ontario and is frequently paired with HEC-RAS to produceflood plain mapping across North America. Outputs from the developed hydrologic model were applied asboundary conditions in the subsequent hydraulic modelling and floodplain mapping of the area(documented in the March 2020 Technical Report title ‘Wingham and Area Flood Plain Mapping’ preparedby GeoProcess for the MVCA.)

2. Hydrologic Setting

The hydrologic study area and modelling extents correspond to the upper Maitland River watershedboundary (Map 2). This area drains a total of 1670 km² before draining to Lake Huron by way of the LowerMaitland River. The study area is bounded by the Nith and Conestogo Rivers (the headwaters of the GrandRiver) to the east, the North Thames watershed and portions of the South Maitland River to the south, andTeeswater and Saugeen watersheds to north.

The Provincial Digital Elevation Model (ONMRF, 2016) for the study area is shown on Map 2. Elevation variesfrom 450 masl in the headwaters of the Maitland in Wellington North, to 300 masl in the reach below thecommunity of Wingham. The topography is gently sloping east to west, with the Middle Maitlandsubwatershed exhibiting a lower slope and a correspondingly higher drainage density.



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2.1. Land Cover

The land cover within the hydrologic study area was evaluated with the Southern Ontario Land ResourceInformation System (SOLRIS v2.0) compiled by MNRF (2014) shown on Map 3. Land use is primarily rural,with limited pockets of built-up (impervious and pervious) lands associated with villages and hamletscovering less than 1% of the area, and with 2.3% of the land cover is dedicated to roadways. Land cover inthe area is dominated by agriculture, with 80.6% of the area classed as either ‘Tilled/Plantation’ or‘undifferentiated’ suggesting either high or low intensity agricultural activities. Forested areas constitute anadditional 4.2% of the study area, with the remaining 11.8% classed as wetlands or water features with themajority classed as treed swamps (10.7%).

Both the regional and local land cover mapping products can assist with the characterization of thehydrologic system and estimate runoff/infiltration within the study area. Critically, anthropogenic andvegetative land cover can strongly influence the hydrologic response of the system by way of several keyparameters. Imperviousness controls runoff from hard surfaces and can be estimated directly from the landcover mapping (i.e., built-up areas and roads). The vegetation classes provided in the land cover mappingare used to infer parameters such as vegetation type, vegetation cover density, rooting depth and soilmoisture storage. The role of shallow subsurface stormflow (interflow) is also controlled by a combinationof factors such as land cover and soil type.

2.2. Soil Classification

Agricultural soils mapping produced by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA,2003) can aid in the characterization of the shallow subsurface conditions. This mapping coverage tends tofocus on the value of the mapped soil families for agriculture use. Soils mapping provides texturalclassifications of the upper soil horizon, descriptions of the drainage properties of the mapped unit, andother agricultural related parameters (e.g., land steepness, stoniness, erosion potential).

As shown on Map 4, the majority of the study area is mapped as loam to silty-loam associated with theHarriston group. The Harriston Loam is a well-drained, dark brown loam with medium to low organic mattercontent (Hoffman et al., 1952). The Harriston Silt-Loam lies to the south of the study area and is similarlyconsidered to be a well-drained soil, despite a larger proportion of silt than the loam profile to the north.Clay loam is found at the south extent of the hydrologic study area, corresponding to the Perth andBrookston soil families. These poorly-drained units overlay thick (5-20 inch) deposits clay (Hoffman et al.,1952) with the Brookston soils demonstrating poorer drainage than the Perth group. The study area istransected by recent alluvial deposits and bottom lands (i.e., stream channels), shown as unmapped regionsin the soils complex mapping. The parent till in the area is typically described as Elma Till; a stoney sandysilt to silt till dating to the last glacial maximum during the late Wisconsin, 25000–21000 years before present(OGS, 2010).

In a hydrologic context, the loam and silt-loam correspond to a ‘B’ type hydrologic group subject tomoderate infiltration when thoroughly wet. The drainage of clay loams varies, with the Perth soils correlatingto a ‘C’ type and the Brookton a ‘D’ type - both of these units exhibit slow and very slow infiltration rates,respectively. Areas with lower infiltration rates correspond to areas with a higher potential to generate runoffduring storm events.



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2.3. Streamflow Monitoring Network

A total of 9 active and historical streamflow gauging stations are available within the hydrologic study areafor characterization and model calibration purposes. Map 5 presents the location of available streamflowgauges with delineated catchment boundaries. Gauge properties obtained from the ECCC HYDAT database(ECCC, 2019) are presented in Table 1. Note the period of available record is not continuous at all stations.

Table 1: Properties of ECCC stream gauge stations within the hydrologic study area.

ID Station NameDrainage

Area(km²)

Easting(m)

Northing(m)

Period ofRecord

02FE002 MAITLAND RIVER BELOW WINGHAM 1640 473,778 4,859,346 1953-201902FE003 MIDDLE MAITLAND RIVER NEAR LISTOWEL 73.4 502,201 4,841,578 1953-201902FE005 MAITLAND RIVER ABOVE WINGHAM 527 478,773 4,862,475 1953-201902FE007 LITTLE MAITLAND RIVER AT BLUEVALE 340 479,867 4,855,731 1967-201902FE008 MIDDLE MAITLAND RIVER NEAR BELGRAVE 645 475,318 4,851,137 1967-201902FE010 BOYLE DRAIN NEAR ATWOOD 205 493,966 4,835,928 1967-201902FE011 MAITLAND RIVER NEAR HARRISTON 112 508,624 4,861,195 1981-201902FE013 MIDDLE MAITLAND RIVER ABOVE ETHEL 416 489,960 4,840,604 1983-201902FE017 LAKELET CREEK NEAR GORRIE 79.4 494,918 4,859,982 2005-2019

2.4. Rainfall Network

An extensive database of climate observations was provided by MVCA for use in this study. MVCA employsthe HEC-DSS database format to store environmental data such as precipitation, temperature, water levels,and streamflow. The DSS format provides for a high degree of interoperability between USACE softwareproducts such as HEC-HMS, and the database can be accessed directly from the model interface. Data from45 precipitation gauges are available within the database, spanning the entirety of MVCA and severaladjacent conservation authorities. From the database, 22 stations within or adjacent to the study area wereselected for inclusion within this study, shown on Map 6. Climate station properties are presents in Table 2.

The temporal resolution of the provided data varies from 1-hour to 5-minutes primarily based on vintage.Stations with multiple timeseries of differing timesteps were merged within the database for ease of use andQA/QC purposes. Note that most of the precipitation data collected at these stations is obtained withunheated tipping buckets and accordingly the data collected during snowfall and mix precipitation eventsare considered less reliable.

Hourly precipitation data was obtained from the ECCC climate network for the study area and surroundingregion. The only station inside the model boundary with sub-daily rainfall data was the discontinuedWROXETER gauge (ID: 6129660) operated between June 1966 and February 1975. The closest active station isMOUNT FOREST (AUT) (ID: 6145504) operated since 2003. Hourly data from this station (or an adjacentequivalent) is captured within the MVCA DSS database, therefore additional ECCC precipitation data was notadded to the climate database employed in this study. These data have been included for future reference inthe supporting digital files transmitted with this report.



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Table 2: Properties of rainfall gauges from MVCA-DSS database employed in this study.

Name Easting (m) Northing (m) Period ofRecord

Belgrave 475,314 4,851,134 1987-2019Blyth 462,700 4,845,355 1987-2019Boyle 493,960 4,835,925 2002-2019Ethel 489,958 4,840,588 1987-2019H1 525,266 4,861,183 2010-2019H8 513,308 4,861,733 2015-2019

Harriston 508,614 4,861,186 1987-2019L5 511,165 4,844,259 2010-2019

Lakelet 494,917 4,859,972 2005-2019Lambert 500,933 4,826,118 2016-2019Listowel 502,197 4,841,565 1987-2019

Lucknow A 458,829 4,868,160 1986-2019Mitchell 483,260 4,810,852 2010-2015

Molesworth 498,953 4,848,089 2014-2019Mt Forest 516,885 4,868,841 2010-2015

Palmerston 511,755 4,852,781 2016-2019Seaforth 467,981 4,821,464 2013-2019

Teeswater 477,246 4,871,976 2010-2015Walton 477,477 4,839,491 2017-2019

Wingham A 478,771 4,862,501 1987-2019Wingham B 473,796 4,859,341 2002-2019

Wroxeter Davis 487,783 4,856,744 2005-2019

3. Model Structure

The following describes the structure of the hydrologic model developed to simulate flood flows throughthe Wingham study area. The following section describes the spatial discretization of the model, the selectedhydrologic processes incorporated in the model, the parameterization approach, and the climate forcingfunctions.

3.1. Model Code

The modelling code employed in the study is the Hydrologic Modelling System (HEC-HMS) version 4.3developed by the US Army Corps of Engineers. HEC-HMS is designed to simulate the complete hydrologicprocesses of dendritic watersheds like the Maitland River. The code includes many hydrological analysisprocedures and includes a variety of mathematical models for simulating precipitation, evapotranspiration,infiltration, excess precipitation transformation, baseflow, and open channel routing. The model can beoperated on either a continuous- or event-basis at time steps ranging from 1 minute to 1 day. The code alsoincludes tools to assist with model calibration and a graphical user interface to facilitate data entry and



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analysis of model results. For a detailed description of the model code, its function, and the many includedsimulation methods the reader is referred to the user manual (USACE, 2018) and the technical referencemanual (USACE, 2000).

3.2. Calibration Catchments

Four of the gauged catchments were selected to characterize runoff from the study area and to supportmodel calibration. The selected catchments represent almost the entire model area (Map 5) and allow thepredictive power of the rainfall-runoff model to be tested to a reasonable level. While further considerationof the other active gauges in the study area (see Section 2.3) was beyond the scope of this project, theseadditional gauges present an opportunity for further calibration/validation of the model should the needarise in the future.

Table 3: Selected streamflow gauges for model calibration and validation.

Role ID Station NameDrainage

Area(km²)

Easting(m)

Northing(m)

Period ofRecord

Calibration 02FE005 MAITLAND RIVER ABOVE WINGHAM 527 478,773 4,862,475 1953-2019Calibration 02FE007 LITTLE MAITLAND RIVER AT BLUEVALE 340 479,867 4,855,731 1967-2019Calibration 02FE008 MIDDLE MAITLAND RIVER NEAR BELGRAVE 645 475,318 4,851,137 1967-2019Validation 02FE002 MAITLAND RIVER BELOW WINGHAM 1640 473,778 4,859,346 1953-2019

As the mechanics of channel routing form the focus of the subsequent local-scale 2D hydraulic modelling(GeoProcess, 2020), only minor emphasis has been placed on channel routing within the hydrologic model.Accordingly, the furthest downstream gauge (02FE002) was used for model verification and validationpurposes. The remaining three gauges were employed in direct calibration, representing 91% of the modelarea.

3.3. Spatial Discretization

The hydrology study area was divided into a series of subbasins (or “hydrologic response units”) to simulatedrunoff at various locations across the model space. Each point of interest is identified as an inspection pointwithin the model space and must have its own subbasin, including calibration streamflow gauges and reachesneeded for input into the 2D hydraulic model. Map 7 presents the boundaries of the hydraulic modeldeveloped for the Wingham area. Note that inspection points within the hydrologic model are required atthe upstream end of each simulated reach in the 2D hydraulic model. An inspection point was also be placedat the downstream end of the 2D hydraulic model area for verification purposes. The location of the threecalibration and one validation/verification streamflow gauges are also shown on Map 7. The properties ofthe 8 inspection points are presented in Table 4.



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Table 4: Hydrologic model inspection points for subbasin delineation.

Name Purpose Easting(m)

Northing(m)

02FE002 Calibration 473,800 4,859,36802FE005 Calibration 478,815 4,862,48302FE007 Calibration 479,885 4,855,75002FE008 Calibration 475,281 4,851,145POI_DS Hydraulic Model Inflow 469,720 4,860,274POI_EAST Hydraulic Model Inflow 477,410 4,859,615POI_SOUTH_EAST Hydraulic Model Inflow 475,338 4,856,460POI_SOUTH_WEST Hydraulic Model Outflow 474,300 4,856,280

Modelled subbasins were delineated using an 8-direction descent procedure (Tarboton, 1997), the ProvincialDigital Elevation Model (ONMRF, 2016) and Ontario Hydro Network watercourse mapping (OMNRF, 2019).The 8 delineated model basins (hydrologic response areas) are presented on Map 8 with the 2D hydraulicmodel boundary and on Map 9 relative to the hydrologic study area.

Table 5: Spatial properties of hydrologic basins included within the HEC-HMS model.

Name DrainageArea (km²)

CentroidDrains to:Easting

(m)Northing

(m)02FE002 26.9 475,460 4,858,730 POI_DS02FE005 529 503,348 4,859,866 POI_EAST02FE007 335 497,135 4,849,137 POI_SOUTH_EAST02FE008 647 494,531 4,835,959 POI_SOUTH_WESTPOI_DS 31.8 471,593 4,861,461 Out of ModelPOI_EAST 27.5 479,889 4,859,993 02FE002POI_SOUTH_EAST 59.1 479,818 4,851,101 02FE002POI_SOUTH_WEST 17.8 473,871 4,854,057 02FE002

Modelled basins are linked together with a series of reaches and junctions. Reaches serve to route waterdownstream while junctions merge multiple sources of inflow into a single outflow. The drainage structureof the model is presented on Figure 1.



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Figure 1: Upper Maitland HEC-HMS model spatial structure.

Routing within the model is simulated with the Muskingum-Cunge method. Streams are represented asrectangular channels within the model. Properties were obtained from air photo interpretation andinspection of the Ontario Hydro Network watercourse layer. Reach properties are summarized in Table 8.As noted above, the purpose of the hydrologic model is to estimate event-based flows on a regional-scaleand therefore employs a relatively simplistic representation of channel routing. A more rigorous andadvanced representation of channel routing in the vicinity of the Town of Wingham is presented in thecompanion report documenting the flood plain mapping analyses using the 2D hydraulic model(GeoProcess, 2020).

Table 6: Simulated reach properties.

Name Length(m)

Width(m)

Slope(m/m)

Manning'sRoughnessCoefficient

Reach-1 8887 22 0.00102 0.065Reach-2 1033 23 0.00222 0.065Reach-3 6639 17 0.00212 0.065Reach-4 4700 28 0.000612 0.065Reach-5 1404 34 0.00285 0.065Reach-6 4583 33 0.00144 0.075Reach-7 5184 32 0.00165 0.085

Neither reservoirs nor lakes have not been explicitly represented as hydraulic features within the model asfunction of project scope. While less representative, this simplified approach favours a more conservativerepresentation of the flood propagation through the upper Maitland River watershed.

POI_DS

REACH 5

02FE002

02FE005

POI_EAST

02FE007

POI_SOUTH_EAST

02FE008POI_SOUTH_WEST

REACH 1

REACH4

BASIN

Junction

REACH

Linkage



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3.4. Process Representation

HEC-HMS offers a number of methods to simulate the hydrologic processes occurring in the model space.Each method has differing assumptions and varying complexity. The methods selected for the upperMaitland model are typical of lumped catchment models. One of the most critical methods is the ’Transform’method which simulates runoff via the two parameter Clark Unit Hydrograph method. Table 7 presents themethods employed in this study. All basins within the model were represented with the same methods.

Table 7: Hydrologic methods selected in HEC-HMS with initial values.

Process Area HEC-HMS Method Parameter Initial ValueModifiedDuring

Calibration

Canopy (Interception storage/ET) Simple Canopy

Initial Storage 30% NoMax Storage Calculated by basin No

Surface (Depression storage) Simple Surface

Initial Storage 50% NoMax Storage 2.5 mm No

Loss (Infiltration/Percolation) Deficit and Constant

Initial Deficit 10 mm NoMaximum Storage Calculated by basin YesConstant Rate Calculated by basin NoImpervious Calculated by basin No

Transform (Runoff) Clark Unit Hydrograph

Time of Concentration Initially estimatedwith the Airport

Method

Yes

Storage Coefficient Yes.

Baseflow (Slow interflow/baseflow) Linear Reservoir

Initial GW1 RateDerived from

hydrograph analysis NoGW1 CoefficientInitial GW2 RateGW2 Coefficient

3.5. Parameterization

Where possible, model basin parameters were set to uniform default values (Table 7), such as initialdepression storage (fixed at 50%). Where necessary, basin parameters were estimated from the regionalland cover (Map 3) and soils mapping (Map 4). Parameters are first distributed by lookup values based onthe unit class then averaged over model basin area. For example, the Max Storage parameter within thecanopy method controls the volume of water that can be held in interception storage. This parameter isdistributed across the model space based on the SOLRIS land cover mapping with the typical lookup valuespresented in Table 8. This results in a refined map of canopy storage estimated for the model area, as shownin Map 10. These values can then be averaged within each basin to produce parameter values for input intothe model.



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Table 8: SOLRIS land cover parameter lookup values.

Class Label ClassCode

RunoffCoefficient

PercentImpervious

(%)

CanopyStorage(mm)

SoilDepth(mm)

Forest 90 0.25 0 4 600Coniferous Forest 91 0.25 0 4 600Mixed Forest 92 0.25 0 4 600Deciduous Forest 93 0.25 0 4 600Treed Swamp 131 0.05 0 3 300Thicket Swamp 135 0.05 0 3 300Fen 140 0.05 0 2 200Bog 150 0.05 0 2 200Marsh 160 0.05 0 2 200Open Water 170 0.05 0 0 25Plantations - Tree Cultivated 191 0.25 0 4 600Hedge Rows 192 0.25 0 4 600Tilled 193 0.35 0 2 100Transportation 201 0.95 80 2 25Built-Up Area - Pervious 202 0.35 40 2 50Built-Up Area - Impervious 203 0.65 70 2 50Extraction - Aggregate 204 0.60 50 0 25Undifferentiated 250 0.28 0 2 100

With this method, the SOLRIS land cover mapping (Map 3) was employed to produce spatially distributedestimates of runoff coefficients (Map 11), imperviousness (Map 12), and soil rooting depth (Map 13).Similarly, the soil texture mapping (Map 4) was employed to produce spatially distributed estimates ofpercolation (infiltration) rates, soil wilting point (Map 14), soil porosity (Map 15), and the available soilmoisture storage (Map 16 – derived by multiplying the soil depth Map 13 by the ratio of plant available water(porosity minus field capacity)). Soil texture lookup values are based on Rawls et al. (1983) and Saxton andRawls (2006) and are summarized in Table 9.



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Table 9: Soil texture parameter lookup values.

‘A’ Horizon Texture ClassCode

UnsaturatedPercolation

Rate(mm/hr)

Porosity FieldCapacity

WiltingPoint

PlantAvailable

Water

Urban/Water 0.74 0.43 0.32 0.08 0.35Clay Loam CL 0.48 0.31 0.28 0.13 0.18Fine Sandy Loam FSL 2.6 0.42 0.20 0.07 0.35Gravelly Sand GS 53 0.44 0.06 0.04 0.40Loam L 1.7 0.43 0.32 0.08 0.35Organic ORG 0.16 0.60 0.30 0.18 0.42Silt Loam SIL 3.2 0.49 0.35 0.10 0.39Silty Clay SICL 1.1 0.42 0.34 0.15 0.27Sandy Loam SL 5.5 0.40 0.18 0.05 0.35Variable VAR 0.74 0.43 0.32 0.08 0.35

Each of the distributed layers was averaged within each model basin to produce parameter values for inputinto the model. Table 10 summarizes the basin parameters derived from the spatial analysis and employedas initial estimates within the model. Initial Time of Concentration values were calculated for each modelbasin with the Airport method as described by MTO (1997) (Table 11).

Table 10: Initial basin parameters calculated from spatially distributed soil and land cover properties.

Name Area(km²)

PercentImpervious

(%)

RunoffCoefficient

CanopyStorage(mm)

Max SoilStorage(mm)

UnsaturatedPercolation

Rate(mm/hr)

02FE002 26.9 8.8% 0.340 2.17 25.9 2.1402FE005 529 2.3% 0.301 2.24 28.1 2.0802FE007 335 2.3% 0.310 2.22 26.6 2.1302FE008 647 2.7% 0.331 2.15 21.1 1.67POI_DS 31.8 2.9% 0.263 2.42 35.8 2.50POI_EAST 27.5 1.9% 0.278 2.35 33.1 1.73POI_SOUTH_EAST 59.1 1.9% 0.308 2.28 29.5 1.97POI_SOUTH_WEST 17.8 1.5% 0.303 2.27 30.0 2.48



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Table 11: Calculated initial basin estimates of Time of Concentration.

Name Area (km²) RunoffCoefficient

StreamLength

(m)

WatershedSlope(m/m)

Time ofConcentration

(hrs)

02FE002 26.9 0.340 3294 0.0023 3.902FE005 529 0.301 77842 0.0016 2202FE007 335 0.310 65495 0.0014 2102FE008 647 0.331 81245 0.0012 24POI_DS 31.8 0.263 1404 0.0029 2.6POI_EAST 27.5 0.278 4583 0.0014 5.7POI_SOUTH_EAST 59.1 0.308 6639 0.0021 5.9POI_SOUTH_WEST 17.8 0.303 8887 0.0010 8.7

3.6. Climate Forcing

Precipitation data from the 22 stations presented in Table 2 were employed as inputs to the hydrologicmodel. An inverse distance squared method was specified to compute basin weighted precipitation values.HEC-HMS internally interpolates and converts the available rainfall data the required temporal resolution forsimulation. To improve the spatial resolution of the interpolated estimates of precipitation, each basin wasfurther subdivided to produce interpolation zones that spanned no more than 15 km. This resulted in thegeneration of 15 interpolation zones as shown on Map 17 and summarized in Table 12.

Table 12: Meteorological interpolation zones.

Name Area(km²)

Percentageof Basin

CentroidsEasting

(m)Northing

(m)02FE005_MET1 127 24.1% 488,135 4,860,51702FE005_MET2 174 32.9% 499,445 4,860,06702FE005_MET3 227 43.0% 514,865 4,859,34802FE007_MET1 66 19.7% 484,692 4,852,01402FE007_MET2 195 58.3% 495,813 4,847,98302FE007_MET3 73.8 22.0% 511,760 4,849,61802FE008_MET1 101 15.7% 477,973 4,844,78902FE008_MET2 144 22.3% 485,978 4,835,04302FE008_MET3 184 28.5% 503,806 4,840,47702FE008_MET4 217 33.5% 500,073 4,828,604MAITLAND RIVER BELOW WINGHAM 26.9 100% 475,460 4,858,730POI_DS 31.8 100% 471,593 4,861,461POI_EAST 27.5 100% 479,889 4,859,993POI_SOUTH_EAST 59.1 100% 479,818 4,851,101POI_SOUTH_WEST 17.8 100% 473,871 4,854,057



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Mean daily temperature was interpolated from adjacent ECCC climate stations and included in the model tosupport the simulation of evapotranspiration where necessary.

4. Calibration and Validation

To support the calibration of the upper Maitland model, instantaneous data at each of the four calibrationstreamflow gauges (Map 9) were obtained for the period spanning January 1969 through November 2019from the Ontario Region of the National Hydrological Services. These data were incorporated into a HEC-DSS database file for input into HEC-HMS and future use by MCVA.

The streamflow records at these stations were inspected for summer and early-fall storm events. While thepeak annual flows in the upper Maitland usually occur in the spring during freshet conditions, the specifiedregulatory event (Hurricane Hazel) is based on a rainfall-only condition. The three largest rainfall-only eventsin the past 15 years were selected for model calibration and validation, namely large runoff events occurringin September 2008, June 2015, and June 2017. The June 2017 event brought significant flooding to thecommunity of Wingham and exhibited more than double the peak flows at the downstream WSC gauge(02FE002) relative to the September 2008 and June 2015 events.

Specifications for the three event scenarios are presented on Table 13, each simulation was conducted on a30-minute timestep. To account for antecedent conditions, evapotranspiration was considered within thesescenarios via the (daily) Priestly Taylor method. An initial simulation start-up period of several weeks tomonths was included in each of the three scenarios to account for antecedent soil moisture, depressionstorage, and canopy storage prior to each major rainfall event.

Table 13: Calibration/validation simulation specifications and calibration statistics.

EventName

Simulation PeriodPurpose Catchment

Peak Discharge(m³/s)

Nash-Sutcliffe

EfficiencyFactorStart Date End Date Observed Simulated

June 2017 14May2017 31Jul2017 PrimaryCalibration

02FE008 135 130 0.8602FE007 118 115 0.9202FE005 412 376 0.9702FE002* 508 657 0.88

June 2015 17May2015 23Jun2015 SecondaryCalibration

02FE008 98.2 69.9 0.7002FE007 71.7 59.1 -0.0702FE005 54.6 65.8 -0.3802FE002* 183 196 0.82

September 2008 01May2008 29Sep2008 Validation

02FE008 59.7 64.6 0.9802FE007 33.2 21.6 0.6802FE005 88.2 82.4 0.8002FE002* 177 227 0.85

* Indicates a validation gauge.

The June 2017 event served as the primary calibration event, with some comparatively minor refinement ofthe model undertaken based on the June 2015 event. The September 2008 event was reserved for modelvalidation, following the split-sample approach (Klemeš, 1986). Within the gauge pool, the downstreamgauge 02FE002 (MAITLAND RIVER BELOW WINGHAM) was treated as a validation gauge within each



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scenario (i.e., no model parameters were modified to improve the response at this gauge). The response atthis downstream gauge is largely representative of the combined flows from the upstream catchments,however, some information regarding the predictive power of the model is captured by this gauge.

Two objective functions were employed to test model fitness during calibration: (1) the match to simulatedversus observed event peak streamflow, and (2) the Nash-Sutcliffe efficiency (NSE) factor (Nash & Sutcliffe,1970). A NSE value of 0.6 is considered reasonable (Chiew & McMahon, 1993) while the peak streamflowdifference is ideally zero.

Model calibration was largely conducted in a manual fashion. The primary parameters adjusted duringcalibration were the Time of Concentration and Storage Coefficients (part of the Transform Method).Additionally, the Maximum Storage parameter within the Loss Method was halved over the course of themodel calibration, reducing the capacity of the soil zone to store water and generating more runoff from themodelled basins. No other model parameters were adjusted from their initial values. Figure 2 presents thesimulated match to observations of streamflow during the June 2017 event. A good match to peaks andvolumes is observed at 02FE005 and 02EF007. The match to the storm volume at 02FE008 is less ideal, likelyowing to the influence of the Bluevale Dam immediately upstream of the gauge (this structure is not explicitlyrepresented in the model). The model overpredicts the peak flow at the downstream gauge 02FE002.

Figure 2: Simulated vs. observed streamflow during the June 2017 flood event (calibration scenario 1).

Figure 3 presents the simulated match to observations of streamflow during the June 2015 event. This eventrepresents a multi-day precipitation event, resulting in a complex runoff response. An adequate match topeaks and hydrograph shape is seen at the calibration gauges (02FE005, 02FE007, 02FE008). Total stormvolumes at 02FE007 and 02FE008 are under predicted, resulting in a lower than desired NSE. An excellentmatch to overall response is seen at the downstream validation gauge (02FE002), with a good match tomultiple peaks over the multi-day event.



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Figure 3: Simulated vs. observed streamflow during the June 2015 flood event (calibration scenario 2).

Figure 4 presents the simulated match to observations of streamflow during the September 2008 validationevent. A good match to the runoff response is observed at all gauges, with an overprediction of the eventpeak apparent at 02FE005 and 02FE002. The 2008 event predates the expansion of the climate network inthe upper Maitland Watershed which may partially account for the observed overprediction at 02FE005.

Figure 4: Simulated vs. observed streamflow during the Sept 2008 flood event (validation scenario).



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Based on the above calibration/validation exercise, the model is fit for the purpose of estimating regulatoryflood flows within the model bounds. The model adequately matches peaks and volumes across severalgauges within the pool and demonstrates high Nash-Sutcliffe efficiency factors (Table 13) during multiplerainfall scenarios. Generally, the model overpredicts storm peaks, erring on the side of conservatismappropriate for this study.

5. Hurricane Hazel Regional Regulatory Event

The calibrated upper Maitland River model was employed to simulate the regulatory flood flows. Theregulatory flood within the MVCA jurisdiction is the larger of the Hurricane Hazel storm or the 100-year flood(O.Reg. 164/06). Analysis of the 100-year return period is presented in GeoProcess (2020). The specifiedhyetograph for the 48-hour Hurricane Hazel event is presented on Table 14, reproduced from the MTODrainage Management Manual (1997).

Table 14: 48-Hour Hurricane Hazel hyetograph (MTO, 1997).

HourRainfall

Total(mm)

1-36 7337 638 439 640 1341 1742 1343 2344 1345 1346 5347 3848 13

Total 285 mm

As per the DMM and the River & Stream Systems Flooding Hazard Limit Technical Guide (MNR, 2002), theHazel rainfall totals in basins with an area greater than 25 km² shall be reduced based on predefined arealreduction factors. The equivalent circular area method was employed for this analysis, with the equivalentarea calculated from the longest watershed length (derived from the Ontario Hydro Network watercourselayer). Areal reduction factors were interpolated from Table D-3 in the Technical Guide (MNR, 2002). Final48-hour rainfall totals for the regulatory event are presented on Table 15 with supporting values for eachbasin.



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Table 15: Model basin reduction factors and total Hurricane Hazel 48-hour storm depths.

Name Area(km²)

WatershedLength(km)

EquivalentCircle Area

(km²)

ReductionFactor

Total 48hrDepth(mm)

02FE002 26.9 54.3 2316 70.2 200.102FE005 529 49.2 1901 73.3 208.902FE007 335 40.7 1301 76.6 218.302FE008 647 43.6 1493 76.6 218.3POI_DS 31.8 58.3 2669 69.0 196.7POI_EAST 27.5 50.6 2011 71.7 204.3POI_SOUTH_EAST 59.1 44.7 1569 74.4 212.0POI_SOUTH_WEST 17.8 47.2 1750 73.3 208.9

The 48-hour storm hyetograph was applied to the calibrated model, scaled within each basin by thecalculated reduction factors in Table 15. The simulation was conducted at a 30-minute time step with a totalduration of 10-days. No evapotranspiration losses were considered during the regulatory flood simulation.Simulated streamflow results at the model inspection points (corresponding to the model boundaries of the2D hydraulic model) are shown in Figure 5.

Figure 5: Simulated regulatory flood flows at model inspection points.



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The hydrographs produced at the model inspection points form the basis of the boundary conditions for the2D hydraulic model. The simulated streamflow at each of the three inflow points of the hydraulic model areprovided in Appendix D of GeoProcess (2020).

6. Model Files and Supporting Documentation

This report is accompanied by a series of digital files containing the final model, forcing data, supporting GISdata, supporting climate and streamflow observations, and a copy of the model code and documentation.These files have been transferred to MVCA in a ZIP file titled 20200218 - HEC HMS - Maitland River Model &Data (GeoProcess).zip with a file size of 835 MB (876,399,817 bytes). Table 16 presents a summary of thecontents of this file by directory structure.

Table 16: Contents of ‘20200218 - HEC HMS - Maitland River Model & Data (GeoProcess).zip’.

Directory Description

…\Maitland_River_at_Wingham\ HEC-HMS Model Files.

…\HEC-HMS (4.3) Executable\ Installation Files to install HEC-HMS version 4.3 on a Windowsmachine.

…\GIS\Shapefiles corresponding key model features such as delineatedcatchments, stream network, meteorological interpolation zones,and gauge/climate stations.

…\GIS\Parameterization\ Supporting GIS files associated with catchment delineation andmodel parameterization.

…\MVCA_DSS\HEC-DSS database file provided by MVCA containing historicalprecipitation and streamflow observations (required foroperation of the HEC-HMS model).

…\GRA_DSS\HEC-DSS database file containing supplemental observationtimeseries data required by the HEC-HMS model, namelyinstantaneous streamflow and daily climate data.

…\GRA_DSS\Daily Climate - 75km Radius -MSC (1865-2019)\

Daily climate data obtained from MSC for stations within a 75 kmradius of the model centroid obtained October 2019.

…\GRA_DSS\FlowData - WSC (Dec 2019)\ Instantaneous streamflow data for the calibration watershedsobtained from ECCC December 2019.

…\GRA_DSS\Hourly Precipitation – MSC\ Historical hourly precipitation data for climate stations operatedby ECCC proximal to the study area (not used in this study).

All data are provided in the NAD83(CSRS) UTM coordinate system (Zone 17N) unless otherwise indicated.

6.1. Limitations on Future Use

This model was developed with a relatively narrow focus: to reasonably estimate the flood hydrographthrough the Mainland River and its tributaries near the community of Wingham during a regional (regulatory)storm event. By the nature of this scope, the model may be limited for use in future studies. Any personswishing to employ the model for future work should be aware of the following limitations:

Calibration and validation of the model was limited to rainfall induced stormflow on an event basis.



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Reservoirs and lakes which may attenuate runoff from the study area are not hydraulicallyrepresented within the model.Snowpack and other cold regions processes were not explicitly represented in the model. Thedocumented model is not suitable for simulating runoff during frozen conditions or when snowpackis present.A relatively minor effort was made to calibrate the model in a continuous fashion, other than toapproximate antecedent conditions on a weekly or monthly basis prior to a storm event. The modelshould therefore not be employed in a continuous fashion without further calibration and validation.The model should not be relied upon to simulate low flow or drought conditions.Channel routing within the hydrologic model has been simplified for this exercise. Those interestedin channel dynamics are referred to the 2D hydraulic model developed for the companion analysisto this work (GeoProcess, 2020).The spatial discretization of the model may be coarse for future analyses. Any adjustments to thespatial discretization of the model should be accompanied by an additional calibration and/orvalidation effort.When transferring model parameters to adjacent watersheds, results should be verified against localobservations of streamflow.The rainfall data for this project was provided by MVCA. Some QA/QC of the data has beenundertaken against adjacent ECCC stations, and where necessary, erroneous values removed fromthe database during periods relevant to the three model calibration/validation scenarios. Futureusers are strongly encouraged to undertake their own check of the climate inputs when employingthe meteorological inputs developed for this study in other models.

7. Closing

The above report documents the development of a hydrologic runoff-rainfall model of theupper Maitland River watershed. This work was undertaken to support the update of floodplainmapping for the Maitland River and its tributaries around the community of Wingham. Thisreport documents the development of the hydrologic model, including the discretization and

parameterization of the model domain, and the calibration and validation process using long-termstreamflow and climate station targets. The calibrated model was then employed to simulate the regulatoryflood flow through the reaches of the Maitland River passing through Wingham. Streamflow hydrographswere extracted from the model to serve as boundary conditions within the 2D hydraulic model used for thedelineation of updated floodplain mapping, documented in GeoProcess (2020).



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8. References

Chiew, F.H.S. and McMahon, T.A., 1993. Detection of trend or change in annual flow of Australian rivers. International Journalof Climatology, 13(6), pp.643-653.

Environment and Climate Change Canada (ECCC). 2019. HYDAT SQLite Database. 16th Release dated November 16th, 2019.[Computer File]. (Accessed November 2019).

GeoProcess Research Associates (GeoProcess). 2020. Wingham and Area Flood Plain Mapping. Technical Report prepared forthe Maitland Valley Conservation Authority. Dundas, ON.

Hoffman, D.W., Richards N.R., and F.F. Morwick. 1952. Soil Survey of Huron County. Report No. 13 of the Ontario Soil Survey.Experimental Farms Service, Canada Department of Agriculture and the Ontario Agricultural College.

Klemeš, V., 1986. Operational testing of hydrological simulation models. Hydrological Sciences Journal, 31(1), pp.13-24.

Nash, J.E. and Sutcliffe, J.V., 1970. River flow forecasting through conceptual models part I—A discussion of principles. Journalof hydrology, 10(3), pp.282-290.

Ontario Geological Survey 2010. Surficial geology of Southern Ontario; Ontario Geological Survey, Miscellaneous Release--Data 128-REV ISBN 978-1-4435-2482-7 [Computer File]. Sudbury, ON (Accessed October 2017)

Ontario Ministry of Agriculture and Food and Rural Affairs (OMAFRA). 2003. Soil Survey Complex [Computer File]. Guelph, ON(Accessed October 2017)

Ontario Ministry of Natural Resources (MNR). 2002. Technical Guide - River & Stream Systems Flooding Hazard Limit. WaterResources Section, Peterborough, ON. 118 pp.

Ontario Ministry of Natural Resources and Forestry (MNRF). 2014. Southern Ontario Land Resource Information System(SOLRIS) Version 2.0 [Computer File]. Peterborough, ON (Accessed October 2017).

Ontario Ministry of Natural Resources and Forestry (MNRF). 2016. Provincial Digital Elevation Model. Computer File].Peterborough, ON (Accessed December 2017).

Ontario Ministry of Natural Resources and Forestry (MNRF). 2019. Ontario Hydro Network (OHN) – Watercourse. OMNRFProvincial Mapping Unit [Computer File]. Peterborough, ON (Accessed April 2019).

Ontario Ministry of Transportation (MTO). 1997. Drainage Management Manual. Drainage and Hydrology Section,Transportation Engineering Branch, Quality and Standards Division.

Rawls, W.J., D.L. Brakensiek, N. Miller, 1983. Green-Ampt Infiltration Parameters from Soils Data. Journal of HydraulicEngineering, ASCE 109(1). pp.62–70.

Saxton, K.E. and Rawls, W.J.. 2006. Soil water characteristic estimates by texture and organic matter for hydrologic solutions.Soil science society of America Journal, 70(5), pp.1569-1578.

Tarboton, D.G., 1997. A new method for the determination of flow directions and upslope areas in grid digital elevation models.Water resources research, 33(2), pp.309-319.

US Army Corps of Engineers (USACE). 2000. Hydrologic Modeling System HEC-HMS: Technical Reference Manual. Davis, CA,March 2000. 145pp.

US Army Corps of Engineers (USACE). 2018. Hydrologic Modeling System HEC-HMS: User’s Manual. Version 4.3. Davis, CA,September 2018. 640pp.

KNOWLEDGE RESEARCH CONSULTING 20

Hydrologic Modelling to Support Wingham andArea Flood Plain Mapping

Prepared for Maitland Valley Conservation Authority

March 12, 2020

Prepared by:

Peter John Thompson, MASc, P.Eng. (ON, AB)Hydrologist

Cailey McCutcheon, MASc, P.Eng.River Engineer

Reviewed by:

Michael Takeda, MASc, P.Eng.Hydrogeologist

Jeff Hirvonen, MAScPrincipal

DisclaimerWe certify that the services performed by GeoProcess Research Associates were conducted in a manner consistent with the level of care,skill and diligence to be reasonably exercised by members of the engineering and science professions.

Information obtained during the site investigations or received from third parties does not exhaustively cover all possible environmentalconditions or circumstances that may exist in the study area. If a service is not expressly indicated, it should not be assumed that it wasprovided. Any discussion of the environmental conditions is based upon information provided and available at the time the conclusionswere formulated.

This report was prepared exclusively for Maitland Valley Conservation Authority by GeoProcess Research Associates. The report may notbe relied upon by any other person or entity without our written consent and that of Maitland Valley Conservation Authority. Any uses ofthis report or its contents by a third party, or any reliance on decisions made based on it, are the sole responsibility of that party. GeoProcessResearch Associates accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions takenbased on this report.

Our Project Number P2019-391© 2020 GeoProcess Research Associates

Maps

Map 1: Floodplain study area intersecting the Maitland River and the community of Wingham.

Map 2: Hydrologic study area and model boundary.

Map 3: Spatial distribution of land cover across the model area (from SOLRIS v2.0 MNRF (2015)).

Map 4: Spatial distribution of surface ('A' Horizon) soil texture across the model area (OMNRF, 2003).

Map 5: Active and historical ECCC stream gauges within the model boundary.

Map 6: Rain gauges operated by MCVA proximal to the model boundary.

Map 7: HEC-RAS model boundary with planned hydrologic model inspection points.

Map 8: Delineated model subbasins relative to the HEC-RAS model boundary.

Map 9: Delineated model subbasins.

Map 10: Spatial distribution of interception storage derived from SOLRIS land cover mapping.

Map 11: Spatial distribution of runoff coefficients derived from SOLRIS land cover mapping.

Map 12: Spatial distribution of imperviousness derived from SOLRIS land cover mapping.

Map 13: Spatial distribution of rooting (soil) depth derived from SOLRIS land cover mapping.

Map 14: Spatial distribution of wilting point derived from OMAFRA soil texture mapping.

Map 15: Spatial distribution of porosity derived from OMAFRA soil texture mapping.

Map 16: Spatial distribution of soil moisture storage derived from SOLRIS land coverage and OMAFRA soil texturemapping.

Map 17: Meteorological interpolation zones relative to the model subbasins and boundary.

Documents

Hydrologic Modelling to Support Wingham and Area Flood ...€¦ · flood plain mapping across North America. Outputs from the developed hydrologic model were applied as boundary conditions