A Hydraulic Modeling Framework for Producing Urban Flood Maps for Zanesville, Ohio
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A Hydraulic Modeling Framework for Producing Urban Flood Maps for Zanesville, Ohio Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Jeremiah Lant, B.S. Graduate Program in Geodetic Science The Ohio State University 2011 Dissertation Committee: Doug Alsdorf, Advisor Mike Durand C.K. Shum Copyright by Jeremiah Lant 2011 Abstract This project examines the flooding dynamics of the Muskingum River near the city of Zanesville, Ohio. Simulating various peak flood events using a hydrodynamic model will provide Muskingum County engineers with valuable information regarding inundated areas, extent, and effect on local communities for different flood events. The impact of various Muskingum River flood events, including the 100 year flood, on the urban environment in Zanesville, Ohio is studied. The project provides a useful hydraulic modeling framework that produces urban flooding maps for the city of Zanesville. These flood maps show how water surface elevations and water depths vary spatially and temporally, and provide a more detailed picture of how flood waves move in urban environments. A hydrodynamic model called LISFLOOD-FP is used to simulate river flow and flooding. LISFLOOD-FP is a finite-difference flood inundation model that can accurately model 1D or 2D channel flow along with 2D floodplain flow. LISFLOOD-FP is a well-established hydrodynamic model that has been proven to properly simulate flood inundation for fluvial, coastal, and urban events. Modeling efforts demonstrate that better knowledge of discharge on the Muskingum River provides a valuable insight into how floods travel through the floodplain. The Federal Emergency Management Agency, FEMA, conducts flood insurance studies to identify a community’s flood risk. The flood risk study is based upon statistical data for river flow, storm tides, hydrologic and hydraulic analyses, and rainfall and topographic surveys. The FEMA maps only provide a one-time snapshot of a flood, and do not describe the full extent of the flood event including the spatial and temporal variability ii of various flood events. Questions, such as the changes in flood inundation extent with time for the city of Zanesville, cannot be fully explored using the FEMA maps. It has been shown that accurate mapping of urban flooding events must take hydraulic connectivity and mass conservation into account (Bates, et al., 2005). In other words, extending potential flood elevations along lines of equal elevation given a river elevation, the so-called “Planar GIS method,” may be inadequate for characterizing urban flooding. An alternative approach involves the simulation of hydraulic processes, which would control flooding and inundation patterns in downtown Zanesville given the FEMA 100 year Muskingum River main stem water surface elevation. Such an approach provides the framework, not only for producing dynamic maps of different frequency flood events for the city of Zanesville, but also evaluating the impacts of adding and/or removing structures or changing land use on urban flooding. Model simulations of the 100 year flood defined by FEMA have been created as part of this research. In addition, a 1D HEC-RAS model was built to compare 100 year flood profiles with the 2D LISFLOOD-FP model. The LISFLOOD-FP model agrees with the FEMA flooding map in spatial extent, and in river height predictions to within 1 foot. A 1-D HEC-RAS model also agrees with both the FEMA and LISFLOOD-FP model predictions. Sensitivity tests indicate that a flood wave with a flow rate of 100,000 cubic feet per second would be required to inundate downtown Zanesville. The study of urban flooding on the Muskingum River also represents an opportunity to more fully understand the performance of the upcoming Surface Water Ocean Topography Mission, SWOT, over modest sized rivers in an urban environment. The iii SWOT satellite will measure water surface elevations and inundated areas for fresh water bodies around the world. The importance of flood events, like the 100 year flood, to river communities lies in the understanding and awareness of how peak floods occur and travel, especially in urban environments. From this, steps towards flood control and damage prevention can be made. The fully parameterized Muskingum River model will allow us to (1) produce urban flooding maps for Zanesville, (2) build a framework for sensitivity studies on impacts from urbanization and climate change, and (3) predict inundation throughout Zanesville, a city of 25,000 people. Key Words: hydrodynamic model; LISFLOOD-FP; Muskingum River; urban flooding; FEMA iv Dedication Dedicated to the students at Ohio State University v Ackowledgements Thank you to my advisor Prof. Doug Alsdorf, Prof. Mike Durand, and Dr. Kostas Andreadis for your wisdom and guidance. Your knowledge, insight, and expertise have made this research possible. I have learned so much from each of you. vi Vita 2006………………………………………… B.S. Physics, University of Kentucky 2009 to Present ……………………………...Graduate Research Associate Department of Earth Science, The Ohio State University Fields of Study Major Field: Geodetic Science vii Table of Contents Abstract .............................................................................................................................................. ii Dedication ......................................................................................................................................... v Acknowledgments ........................................................................................................................... vi Vita ................................................................................................................................................... vii List of Tables ................................................................................................................................... ix List of Figures ................................................................................................................................... x Chapter 1: Introduction ................................................................................................................... 1 Chapter 2: Methods.......................................................................................................................... 6 Chapter 3: Research Area and Model Simulations .................................................................... 11 Chapter 4: Results and Discussion .............................................................................................. 22 Chapter 5: Conclusion ................................................................................................................... 38 References ....................................................................................................................................... 40 viii List of Tables Table 1. Range of Friction Coefficients used by FEMA .......................................................... 17 Table 2. Comparison of Water Surface Elevations ................................................................... 23 ix List of Figures Figure 1. Muskingum River Watershed ......................................................................................... 2 Figure 2. Flood Control Structures ................................................................................................ 3 Figure 3. FEMA Flood Map of Downtown Zanesville, Ohio .................................................. 5 Figure 4. Aerial Image of Research Area .................................................................................... 11 Figure 5. Sample Model Inputs .................................................................................................... 13 Figure 6. Processed Digital Elevation Model of Research Area.............................................. 16 Figure 7. Channel and Floodplain Friction Coefficient Map ................................................... 18 Figure 8. Input Hydrographs for FEMA 100 Year Flood Simulation ................................... 20 Figure 9. Triangular Irregular Network Map.............................................................................. 21 Figure 10. Water Surface Elevation Maps of FEMA 100 Year Flood Simulation ............... 25 Figure 11. Water Depth Maps of FEMA 100 Year Flood Simulation ................................... 26 Figure 12. Flood Extent Comparison between FEMA and LISFLOOD-FP ....................... 27 Figure 13. HEC-RAS Outputs of FEMA 100 Year Flood Simulation .................................. 29 Figure 14. Comparison of Water Surface Profiles ..................................................................... 30 Figure 15. Multiple Linearly Scaled Hydrographs ..................................................................... 32 Figure 16. Water Depth Maps ...................................................................................................... 33 Figure 17. Water Depth Map of Major Flood Inundation in Zanesville, Ohio .................... 34 Figure 18. Input Hydrographs for Streamstats 100 Year Flood Simulation.......................... 36 Figure 19. Water Depth Maps of Streamstats 100 Year Flood Simulation ........................... 37 x Chapter 1: Introduction Flooding continues to be a major natural disaster across the United States, capable of great damage and loss to property and life that can occur despite engineering