HYDRAULIC GEOMETRY OF STREAMS & INTRODUCTION OF ELEVATION AS THE NEW STREAM CLASSIFYING PARAMETER...
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HYDRAULIC GEOMETRY OF STREAMS & INTRODUCTION OF ELEVATION AS THE NEW STREAM CLASSIFYING PARAMETER RAJAN JHA, EIT, VIRGINIA TECH ADVISOR : Dr PANOS DIPLAS
HYDRAULIC GEOMETRY OF STREAMS & INTRODUCTION OF ELEVATION
AS THE NEW STREAM CLASSIFYING PARAMETER RAJAN JHA, EIT, VIRGINIA
TECH ADVISOR : Dr PANOS DIPLAS
Slide 2
Outline Hydraulic Geometry of streams - An Overview Stream
classification system- An Overview Compilation of hydraulic
geometric field data- UK, US & Canada streams Grain size (D 50
) based statistical analysis of the field data Elevation based
statistical analysis of the field data Overall conclusion of this
study 2
Slide 3
Hydraulic geometry of streams An overview Hydraulic geometric
equations describe the quantitative variations of stream properties
with changing discharge. [Ferguson, 1986] Leopold and Maddock
(1953) established following hydraulic geometric relations in power
form: w = aQ.5 d = cQ.33 v = kQ.17 Hydraulic geometric variables
considered in this study : Aspect ratio, channel slope &
Sinuosity (All dimensionless) 3
Slide 4
Defining the hydraulic geometric terms Aspect Ratio (Ar) For
any channel or stream, it is defined as the ratio of bankfull width
to bankfull depth 4
Slide 5
Defining the hydraulic geometric terms Channel gradient (Sc)
For any channel or stream, it is defined as the ratio of drop in
the elevation per unit horizontal length 5
Slide 6
Defining the hydraulic geometric terms Sinuosity (P) For any
stream reach, it is defined as the ratio of actual sinuous length
(channel length) to the shortest straight line distance (valley
length). 6
Slide 7
Compilation of hydraulic geometric field data 7 CountryRegions
covered # Data points Type of streams covered based on grain size
Canada Yukon, British Columbia, Alberta, Manitoba, Saskatchewan 92
Sandy, Gravel & Cobble UK Wales, Scotland, Staffordshire,
Lancashire, Herefordshire, Durham county 74Gravel & Cobble
USAArizona, New Mexico, Oklahoma, Navajo, Missouri, Virginia,
Maryland, West Virginia, New York, Montana, Washington state,
Florida, Georgia, Alabama, Tennessee, Colorado, Michigan, Kentucky,
707Sandy, Gravel & Cobble
Slide 8
Stream classification system An overview More than 20 different
stream classification systems have been proposed till date Streams
have been classified on the basis of bed material, patterns, age,
sediment inputs, orders etc Rosgen (1994, 1996) developed a new
approach to channel classification system where he divided the
channels into four hierarchical levels Even with the existence of
so many available classification systems, none of them have been
accepted universally till date 8
Slide 9
Research Objectives Calculating most probable values of Ar, Sc
& P occurring together in nature for each stream type : sandy,
gravel and cobble Introducing elevation above mean sea level as the
new parameter for stream classification system Identifying trends
existing in the behavior of stream variables (Ar, Sc & P) while
moving upstream 9
Slide 10
Median grain size (D 50 ) based analysis of hydraulic geometry
of streams Brief Outline: Dividing field data into sandy, gravel
& cobble groups Application of joint probability distribution
on Ar, Sc, P of each group Finding MPVs of the hydraulic variables
for each group occurring together Analyzing 3-Dimensional plots
10
Modal values of Ar, Sc & P for each stream type Probability
density functions of hydraulic geometric variables were estimated
for each stream type and modal values were calculated 13
Slide 14
Joint probability distribution of Ar, Sc & P Using kernel
density estimation and smoothing on a fine grid in statistical
software R, joint probability plots in 3 dimensional forms were
also obtained for each stream type The peak in the plots represent
the most probable values (MPVs) of the three variables [Ar, Sc, P]
occurring together in the nature for each stream type 14
Slide 15
Joint probability 3-D plots for sandy streams 15 [Ar + Sc][Sc +
P][P +Ar]
Slide 16
Joint probability 3-D plots for gravel streams 16 [Ar + Sc][Sc
+ P][P +Ar]
Slide 17
Joint probability 3-D plots for cobble streams 17 [Ar + Sc][Sc
+ P][P +Ar]
Slide 18
Most probable values of Ar, Sc & P occurring together
18
Slide 19
Elevation based analysis of hydraulic geometry and establishing
it as the new stream classifying parameter Brief Outline: Dividing
complete field data into 14 fine elevation ranges Calculation of
Modal values of Ar, Sc & P for each range Formation of final
fine elevation zones and calculating MPVs for each zone Classifying
sandy, gravel and cobble streams on the basis of the 5 elevation
zones 19
Slide 20
Grouping of data into 14 fine elevation zones 20
Slide 21
Modal values calculated for 14 elevation ranges 21
Slide 22
Formation of final 5 elevation zones 22
Slide 23
MPVs calculated for each of the 5 zones 23
Slide 24
3 Dimensional Probability density plots 24 Presented for
highest elevation zone : 5000 ft & above Rest all zones
followed similar distribution behavior [AR + Sc][Sc + P] [P+
AR]
Summary & Conclusion Statistical analysis is a strong tool
in understanding the co- relation and interdependency existing
amongst the stream variables Elevation provides a consistent
framework for grouping streams on the basis of its hydraulic
characteristics. Thus elevation based classification can be
considered as the new morphology based stream classification
system. 26
Slide 27
Summary & Conclusion Elevation based classification
provides a logical progressive expression of trends occurring in
channel characteristics. MPVs can be very useful for engineers
while designing canals, channels and obtaining representative
dimensions for laboratory and numerical modeling 27
Slide 28
Acknowledgement Dr Panayiotis Diplas- Professor &
Department Chair, Civil & Environmental Engineering, Lehigh
University, (Previously at Virginia Tech) Dr Shrey K. Shahi-
Stanford University NCHRP National Cooperative Highway Research
Program (Funding Agency) 28
Slide 29
Dedicated 29 Dedicated to those who lost their lives in the
tragic incident called Himalayan Tsunami, June 2013, India. More
than 5700 people died and many still missing