Sizing Stream Setback Using GIS Tools for Stream Protection THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Ming Sheng Graduate Program in Environmental Science The Ohio State University 2012 Master's Examination Committee: Dr. Steven Gordon, Advisor Dr. Maria Conroy Dr. Andrew Ward Copyrighted by Ming Sheng 2012 Abstract Administering stream setback ordinances is widely adopted by local governments to maintain the health and integrity of stream systems. A setback is a designated zone within a floodplain where land development that would have negative impact on the stream is strictly prohibited. Given the fact that Geographic Information System (GIS) has been pervasive in support of resources planning and management in many aspects, this study examines the uses of ArcGIS geoprocessing tools in designing properly sized stream setbacks for the Big Darby Creek Watershed. A streamway formula that relies on the drainage area as the single independent variable is applied for setback width calculation. A workflow and various python script modules are developed to implement the operating framework where drainage network is first classified based on stream order and then individual reaches undergo further division based on a user-specified criterion. The recommended criterion requires that the computed setback width difference between the upstream and downstream end of each divided segment be no greater than 10%. The feasibility of implementing the setback widths resulting from the program is evaluated against the existing land uses along the riparian corridors in this watershed. The findings suggest that the designed setback widths are generally practical without severely conflicting with the current land uses. The developed workflow and GIS tool package ii can benefit localities having interest in stream protection, and be applied to any streams in the eastern U.S. iii Dedicated to my husband, Zeng Zhang iv Acknowledgments I am indebted to my advisor, Dr. Steven Gordon, who has been supporting and leading my work throughout my graduate experience. Without his guidance on this project as well as the financial support provided, I would not have the freedom to dive into the amazing world of GIS and Python. I would like to thank my committee members Dr. Ward for the discussion about the stream morphology principles, and Dr. Conroy for her gracious willingness to serve on the committee on short notice. My special thanks go to Dean Djokic and Christine Dartiguenave from ESRI water resources team for their patience in helping me troubleshoot the problems with ArcHydro geoprocessing tools. Also, I would like to express my deepest gratitude to Dr. David R. Maidment from University of Texas at Austin and Dr. Laura Tateosian from North Carolina State University. They generously share their courses online--GIS in Water Resources and GIS Programming Fundamentals respectively, both of which enabled me to grasp the necessary skills to complete this work. Most importantly, I would like to thank my husband Zeng Zhang who always has faith in me, encouraging me and inspiring me. From him, I know what are determination, dedication, and persistence. Without him, I would not have come to where I am today and moreover, would not have become a huge Buckeye fan. I also owe my thanks to my v dear family 8,000 miles away who have always valued knowledge and education and always been by my side regardless of how far apart we are physically. Lastly, I want to thank ESGP for all the support during my study here at The Ohio State University. Especially I thank Maurea Al-khouri for her kind administrative assistances which make the “Ship of Graduation” on the right track towards its destination. vi Vita June 2002 .......................................................Changzhou High School 2006................................................................B.Eng. Environmental Engineering, Nanjing University 2007................................................................M.S. Environmental Science & Engineering, Nanyang Technological University 2007 to 2009 .................................................Engineer, Public Utility Board (PUB) 2010 to present ...............................................Graduate Research Associate, Environmental Science Graduate Program, The Ohio State University Fields of Study Major Field: Environmental Science vii Table of Contents Abstract ............................................................................................................................... ii Acknowledgments............................................................................................................... v Vita .................................................................................................................................... vii List of Tables ...................................................................................................................... x List of Figures .................................................................................................................... xi Chapter 1: Introduction ...................................................................................................... 1 1.1 Overview ................................................................................................................... 1 1.2 Overview of Setback Regulations ............................................................................. 2 1.3Types of setbacks and their scientific bases ............................................................... 5 1.3.1 Riparian Buffer ................................................................................................... 5 1.3.2 Streamway Concept ............................................................................................ 8 1.4 Research Objective .................................................................................................. 14 Chapter 2: Implementation Methodology ......................................................................... 16 2.1 Data and Software ................................................................................................... 16 2.2 Workflow and Scripts.............................................................................................. 19 viii 2.2.1 Terrain Preprocessing ....................................................................................... 22 2.2.2 Breakpoint Identification .................................................................................. 27 2.2.3 Setback Mapping .............................................................................................. 32 Chapter 3: Results and Discussion .................................................................................... 34 3.1 Setback Width Distribution ..................................................................................... 34 3.2 Current Land Use .................................................................................................... 44 Chapter 4: Conclusion....................................................................................................... 49 References ......................................................................................................................... 53 Appendix A: Sizing Setback Tools User Manual ............................................................. 56 Appendix B: Python Scripts.............................................................................................. 68 ix List of Tables Table 1: Acreage of different land covers in the setback riparian zone ............................ 44 x List of Figures Figure 1: Illustration of a 25ft riparian buffer applied to both sides of a stream (Mathews 2006) ................................................................................................................................... 6 Figure 2: Buffer zones along one side of the stream (Wet Weather Solution Program), Kansas City MO .................................................................................................................. 6 Figure 3: Illustration of an 82ft setback designed using streamway concept (Mathews 2006) ................................................................................................................................. 12 Figure 4: Location of the Big Darby Creek Watershed .................................................... 17 Figure 5: Customized toolset "Sizing Setback" storing script tools in the ArcToolbox ... 19 Figure 6: Stream order classification ................................................................................ 21 Figure 7: A sample stream reach constructed by segments and vertices .......................... 22 Figure 8: Terrain Preprocessing Workflow ...................................................................... 23 Figure 9: Flow direction coding (Olivera et al. 2002). Each number is a code representing a direction.......................................................................................................................... 25 Figure 10: Physical representation of flow direction grid and flow accumulation grid (Olivera et al. 2002) .......................................................................................................... 25 Figure 11: Comparison between stream polyline layer downloaded from NHD (left) and the drainage line generated by the terrain preprocessing using the default threshold