Surface Hydrologic Modeling and Analyzing Watershed Hydrologic Response to Landcover Change

154 Pages·2017·3.41 MB·English

by  Roshan Poudel

UNLV Theses, Dissertations, Professional Papers, and Capstones
12-1-2017
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Roshan Poudel
University of Nevada, Las Vegas
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SURFACE HYDROLOGIC MODELING AND ANALYZING WATERSHED HYDROLOGIC
RESPONSE TO LANDCOVER CHANGE

By

Roshan Poudel

Bachelor of Science in Civil Engineering (Specialization: Hydropower)
Kathmandu University
2013

A thesis submitted in partial fulfillment
of the requirement for the

Master of Science in Engineering – Civil and Environmental Engineering

Department of Civil and Environmental Engineering and Construction
Howard R. Hughes College of Engineering
The Graduate College

University of Nevada, Las Vegas
December 2017
Thesis Approval
The Graduate College
The University of Nevada, Las Vegas

August 18, 2017
This thesis prepared by
Roshan Poudel
entitled
Surface Hydrologic Modeling and Analyzing Watershed Hydrologic Response to
Landcover Change
is approved in partial fulfillment of the requirements for the degree of
Master of Science in Engineering – Civil and Environmental Engineering

Department of Civil and Environmental Engineering and Construction

Haroon Stephen, Ph.D. Kathryn Hausbeck Korgan, Ph.D.
Examination Committee Chair Graduate College Interim Dean

Sajjad Ahmad, Ph.D.
Examination Committee Member

Jacimaria Batista, Ph.D.
Examination Committee Member

Ashok Singh, Ph.D.
Graduate College Faculty Representative

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ABSTRACT

Urban flooding is the most frequently occurring disaster in rapidly urbanizing cities. Rapid
urbanization in general, is characterized by an increase in the total impervious surface area, which
means less soil cover for the stormwater to infiltrate and a greater volume of runoff from the area
in case of a storm event. This increased volume of surface runoff, if not drained, results in urban
flooding. Urban flooding can cause serious economic and environmental damages by disrupting
transportation and spreading pollution. It is therefore, essential to understand the cause, behavior
and effects of urban flooding so as to minimize the risks and costs associated with urban floods.

Hydrologic models are useful tools for understanding hydrologic processes and for
designing urban stormwater drainage infrastructure to reduce the risks of floodings. This research
aims to study urban hydrology by estimating surface runoff from an urban area using an event
based distributed parameter hydrologic model. In this research, an event-based distributed
parameter hydrologic model is developed, which uses Green-Ampt infiltration model to estimate
the surface runoff from a given catchment. The developed model is tested on two small catchments.
The ‘rainfall-runoff modeling’ part of the developed model is calibrated for the rainfall events of
May 22, 2017 and, May 24, 2017 over the Moores Run study area, and, validated for the rainfall
event of April 17, 2017. The ‘flood-modeling’ part of the developed model is validated for the
rainfall event of Sep 11, 2012 over the Parking-lots area at UNLV. The results of the rainfall-
runoff simulation and flood depth and extent estimation for different land-cover change scenarios
over the Parking-lots catchment is also provided.

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The testing on Moores Run study area resulted in calibration at 30-m resolution DEM and
a hydraulic conductivity value of 0.19 cm/hr. for soil group D. The error in the model’s estimation
of the catchment area is 7.75%. The model over-predicted the runoff volume from the catchment
for the first rainfall event while under-predicted the runoff volume from the catchment for the
second rainfall event. The average error in estimation of the runoff volume is 1.8%. The model
also over-predicts the ‘time-to-peak’ and under-predicts ‘peak runoff’ in both cases. The average
of RMSE between the predicted hydrograph and actual hydrograph for the two rainfall events is
0.0071 m3/s in calibration, and, 0.011 m3/s in validation. The testing on UNLV Parking-lots area
resulted in calibration at 10-m resolution DEM. For the rainfall event of Sep 11, 2012, the model
predicts over predicts the peak flood depth and under-predicts the maximum extent of flooding.
The error in flood depth estimation is found be 12.9%. From watershed hydrologic response to
landcover change analysis, it is observed that Manning’s roughness coefficient doesn’t affect the
total volume of runoff, however, the time to peak is significantly delayed for landcover with higher
values of Manning’s roughness co-efficient.

This research provides an insight into surface hydrologic modeling. It also provides an
overview of calibration against DEM resolution and hydraulic conductivity values. Finally, it
provides an understanding of watershed hydrologic response to different landcovers with various
Manning’s roughness values.

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DEDICATION

I would like to thank Dr. Haroon Stephen for guiding me throughout my research and for
helping me to write this thesis. I also express my appreciation towards Dr. Sajjad Ahmad, Dr.
Jacimaria Batista, and, Dr. Ashok Singh. I want to express my gratitude to Masih Edalat for his
continuous help in my research. I also want to express my gratitude to Cabel Shrestha for his
guidance and support throughout my graduate studies. Further, I would also like to thank my
family and friends. I wouldn’t be where I am without their help.

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TABLE OF CONTENTS

ABSTRACT--------------------------------------------------------------------------------------------------- III
DEDICATION ------------------------------------------------------------------------------------------------- V
TABLE OF CONTENTS ----------------------------------------------------------------------------------- VI
LIST OF TABLES ------------------------------------------------------------------------------------------- IX
LIST OF FIGURES ------------------------------------------------------------------------------------------- X

CHAPTER 1: INTRODUCTION --------------------------------------------------------------------------- 1
1.1) Research Motivation: ----------------------------------------------------------------------- 3
1.2) Research Objectives: ----------------------------------------------------------------------- 4
1.3) Research Approach: ------------------------------------------------------------------------ 5
1.4) Thesis Outline: ------------------------------------------------------------------------------- 6
CHAPTER 2: LITERATURE REVIEW ------------------------------------------------------------------ 8
2.1) Urban hydrologic modeling --------------------------------------------------------------- 8
2.1.1) Historical and Current practices --------------------------------------------------------- 10
2.1.2) Classification of contemporary hydrologic models ----------------------------------- 13
2.1.2.1) Process based classification -------------------------------------------------------------- 14
2.1.2.2) Time-scale based classification ---------------------------------------------------------- 16
2.1.2.3) Land-use based classification ------------------------------------------------------------ 17
2.1.2.4) Model-use based classification----------------------------------------------------------- 17
2.1.2.5) Solution-technique based classification ------------------------------------------------ 17
2.1.3) Shortcomings of contemporary hydrologic models and modeling practices ------ 18
2.2) Green-Ampt infiltration model and disadvantages of SCS CN model. ------------ 21
2.3) Causes of urban flash flooding ----------------------------------------------------------- 25
2.4) Flooding in Baltimore --------------------------------------------------------------------- 27
2.5) Flooding in Las Vegas --------------------------------------------------------------------- 29
2.6) Summary of Literature review ----------------------------------------------------------- 33
CHAPTER 3: STUDY AREA AND DATA ------------------------------------------------------------- 35
3.1) Study Area ---------------------------------------------------------------------------------- 35
3.2) Data ------------------------------------------------------------------------------------------ 41
3.2.1) Remote Sensing Data ---------------------------------------------------------------------- 41
3.2.1.1) ‘10-m DEM’ for UNLV Parking-lots area. --------------------------------------------- 41
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3.2.1.2) ‘30-m DEM’ of Moores Run Study area. ----------------------------------------------- 41
3.2.1.3) ‘2015 version NAIP imagery (1m resolution)’ ----------------------------------------- 42
3.2.2.1) Rainfall Data -------------------------------------------------------------------------------- 43
3.2.2.2) Soil group data ------------------------------------------------------------------------------ 47
CHAPTER 4: METHODOLOGY ------------------------------------------------------------------------- 52
4.1) Hydrologic modeling ---------------------------------------------------------------------- 52
4.1.1) Data preparation: --------------------------------------------------------------------------- 52
4.1.1.1) Elevation data ------------------------------------------------------------------------------ 53
4.1.1.2) Flow-direction and watershed delineation. --------------------------------------------- 53
4.1.1.3) Hydrological slope ------------------------------------------------------------------------- 54
4.1.2) Modeling: ----------------------------------------------------------------------------------- 55
4.2) Description of the Matlab code for the developed hydrologic model -------------- 57
4.4) Image classification ------------------------------------------------------------------------ 58
4.5) Model calibration and validation -------------------------------------------------------- 58
4.6) Model Implementation/Simulation ------------------------------------------------------ 60
4.7) Error analysis ------------------------------------------------------------------------------- 61
4.8) Landcover change analysis --------------------------------------------------------------- 61
4.9) Summary of methodology ---------------------------------------------------------------- 62
CHAPTER 5: RESULTS------------------------------------------------------------------------------------ 63
5.1) Moores Run study area -------------------------------------------------------------------- 63
5.1.1) Results for DEM resampling and watershed delineation ----------------------------- 63
5.1.2) Results for Image classification ---------------------------------------------------------- 66
5.1.3) Calibration and error analysis. ----------------------------------------------------------- 67
5.1.4) Hydrographs and validation. ------------------------------------------------------------- 71
5.1.5) Discussion ----------------------------------------------------------------------------------- 73
5.2) UNLV Parking-lots area:------------------------------------------------------------------ 76
5.2.1) Results for DEM filtering and watershed delineation -------------------------------- 76
5.2.2) Hydrographs -------------------------------------------------------------------------------- 80
5.2.3) Inundation mapping and Estimation ---------------------------------------------------- 82
5.2.4) Validation of the model ------------------------------------------------------------------- 85
5.2.4.1) Validation for flood depth estimation --------------------------------------------------- 85
5.2.4.2) Validation for flood extent estimation -------------------------------------------------- 86
5.2.5) Discussion ----------------------------------------------------------------------------------- 87
5.3) Landcover change scenarios -------------------------------------------------------------- 89
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5.3.1) Discussion ----------------------------------------------------------------------------------- 95
5.4) Landcover treatment scenarios ----------------------------------------------------------- 97
5.5) Summary of all results --------------------------------------------------------------------- 99
CHAPTER 6 – SUMMARY AND CONCLUSION -------------------------------------------------- 101
6.1) Summary ---------------------------------------------------------------------------------- 101
6.2) Conclusion -------------------------------------------------------------------------------- 102
6.3) Limitations -------------------------------------------------------------------------------- 103
6.4) Recommendations ------------------------------------------------------------------------ 103
APPENDIX - I ---------------------------------------------------------------------------------------------- 107
APPENDIX - II --------------------------------------------------------------------------------------------- 121
REFERENCES --------------------------------------------------------------------------------------------- 129
CURRICULUM VITAE ---------------------------------------------------------------------------------- 141

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LIST OF TABLES

Table 3.2.2-1: Values of hydraulic conductivity for different soil textures -------------------------- 49
Table 3.2.2-2: Manning’s roughness coefficient (n) ---------------------------------------------------- 50
Table 3.2.2-3: Soil properties ------------------------------------------------------------------------------- 51
Table 5.1-2: Summary of outputs for ‘rainfall-runoff’ analysis --------------------------------------- 74
Table 5.3-1: Summary of the landcover change scenarios --------------------------------------------- 96

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