Wood-Pawcatuck Watershed Flood Resiliency Management Plan prepared by AUGUST 2017 Wood-Pawcatuck Watershed Association Acknowledgements We would like to thank the following individuals and organizations for their contributions of time and effort to the development of this plan: Project Steering Committee Ernie Panciera, Water Resources, Rhode Island Department of Environmental Management Carla Feroni, Connecticut Department of Energy and Environmental Protection Elizabeth Ahearn, U.S. Geological Survey Gardner Bent, U.S. Geological Survey Wendy Gendron, U.S. Army Corps of Engineers John O’Brien, The Nature Conservancy Joe Warner, Building/Zoning Official, Town of Charlestown James Lamphere, Town Planner, Town of Hopkinton Ron MacDonald, III, EMA Director, Town of Hopkinton Amy Gryzbowski, EMA Coordinator, Town of Westerly Marylin Shellman, Town Planner (retired), Town of Westerly Henry Oppenheimer, Town Council President, Town of Richmond George Crouse, First Selectman, Town of Stonington Scot Deledda, Town Engineer, Town of Stonington Keith Brynes, Planning Department, Town of Stonington Other Involved Individuals Jessica Stimson, State Hazard Mitigation Officer, RI Emergency Management Agency Susan Kiernan, Water Resources, Rhode Island Department of Environmental Management Jonathan Zwarg, Water Resources, Rhode Island Department of Environmental Management Catherine Sparks, Natural Resources, Rhode Island Department of Environmental Management Phillip Edwards, III, Fish & Wildlife, Rhode Island Department of Environmental Management Wood-Pawcatuck Watershed Association Christopher Fox, Executive Director Denise Poyer, Project Coordinator Zack Valerio and Nate Lukas, URI Coastal Fellows Program (summer interns) Consultant Team Fuss & O’Neill, Inc. – Erik Mas, PE; Maren Frisell, PE; Nils Wiberg, PE, CFM; Phil Moreschi, PE, CFM; David Askew, CPESC; Joshua Wilson, PWS; Celicia Boyden; Rachael Weiter, EIT; Sean Arruda, PE, CFM; William Guenther; Diane Mas, PhD; Robin Casioppo; Sara Berryman; Lora Barlow; Meghan Flanagan Field Geology Services – John Field, PhD, Nicolas Miller Document photos taken and provided by Wood-Pawcatuck Watershed Association. Wood-Pawcatuck Watershed Flood Resiliency Management Plan Table of Contents 1 Introduction .......................................................................................... 1 1.1 The Wood-Pawcatuck Watershed .............................................................................................. 1 1.2 Flooding in the Wood-Pawcatuck .............................................................................................. 1 1.3 Other Issues Facing the Watershed ....................................................................................... 11 1.4 Why Develop a Watershed-Based Management Plan? ...................................................... 11 1.5 A Multi-Benefit Approach to Flood Resiliency ....................................................................... 13 1.6 Organization of this Document ............................................................................................... 13 2 Plan Development Process ............................................................... 14 2.1 Project Partners and Funding .................................................................................................. 14 2.2 Project Steering Committee .................................................................................................... 14 2.3 Technical Assessments ............................................................................................................ 15 2.4 Public Participation and Outreach .......................................................................................... 16 3 Watershed Overview .......................................................................... 18 3.1 Watershed Description ............................................................................................................. 18 3.2 Land Use and Development .................................................................................................... 22 3.3 Physical Characteristics ........................................................................................................... 24 3.4 Ecological Resources ................................................................................................................ 27 3.5 Water Quality ............................................................................................................................. 30 4 Management Recommendations ..................................................... 33 4.1 Dams and Impoundments ....................................................................................................... 35 4.2 Culverts and Bridges ................................................................................................................. 47 4.3 Floodplains and River Corridors .............................................................................................. 62 4.4 Wetlands ..................................................................................................................................... 81 4.5 Stormwater................................................................................................................................. 85 5 Funding Sources ................................................................................ 95 5.1 State Funding Sources ............................................................................................................. 95 5.2 Federal Funding Sources.......................................................................................................... 98 5.3 Other Funding Sources ........................................................................................................... 103 6 References .......................................................................................105 Wood-Pawcatuck Watershed Flood Resiliency Management Plan i List of Tables Table 1-1. Significant rainfall and flooding events in Washington, County, Rhode Island. ................................ 5 Table 1-2. Estimated magnitude of flood flows for selected Annual Exceedance Probabilities (AEP) at selected stream gages on the Pawcatuck River. .................................................................................. 7 Table 3-1. Towns located within the Wood-Pawcatuck watershed..................................................................... 18 Table 3-2. Subwatersheds in the Wood-Pawcatuck watershed. ......................................................................... 20 Table 4-1. Recommendations for dams and impoundments.............................................................................. 39 Table 4-2. High- and medium-priority dam management recommendations. ................................................. 42 Table 4-3. Stream crossing recommendations...................................................................................................... 52 Table 4-4. High-priority stream crossings. ............................................................................................................. 54 Table 4-5. Floodplain and river corridor recommendations................................................................................ 67 Table 4-6. High-priority stream and floodplain restoration sites by project type. ............................................ 69 Table 4-7. Wetland conservation and restoration recommendations. .............................................................. 83 Table 4-8. Stormwater and green infrastructure recommendations. ................................................................ 87 Table 4-9. Proposed green infrastructure retrofit concepts. ............................................................................... 89 List of Figures Figure 1-1. Wood-Pawcatuck watershed. ................................................................................................................. 2 Figure 1-2. Flooding in the Wood-Pawcatuck watershed during March and April 2010. ................................... 3 Figure 1-3. Plot of annual peak discharge at several USGS stream gages in the Wood-Pawcatuck watershed (Field, 2015). ............................................................................................................................................ 7 Figure 1-4. Special Flood Hazard Areas and areas of flooding in the Wood-Pawcatuck watershed................. 9 Figure 3-1. Major subwatersheds of the Wood-Pawcatuck. ................................................................................ 19 Figure 3-2. Land cover in the Wood-Pawcatuck watershed. ................................................................................ 23 Figure 3-3. Percent impervious cover within the Wood-Pawcatuck watershed. ............................................... 25 Figure 3-4. Areas of protected open space within the Wood-Pawcatuck watershed. ...................................... 26 Figure 3-5. Wetland resources in the Wood-Pawcatuck watershed. .................................................................. 28 Figure 3-6. Impaired waterbodies in the Wood-Pawcatuck watershed.............................................................. 31 Figure 4-1. Dams and associated hazard classifications in the Wood-Pawcatuck watershed......................... 36 Figure 4-2. Existing and future hydraulic capacity ratings for assessed stream crossings in the Wood- Pawcatuck watershed. ........................................................................................................................