Stormwater Ponds in Coastal South Carolina
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STORMWATER PONDS IN COASTAL SOUTH CAROLINA 2019 State of Knowledge Full Report Stormwater Ponds in Coastal South Carolina: 2019 State of Knowledge Report 1 STORMWATER PONDS IN COASTAL SOUTH CAROLINA 2019 State of Knowledge Full Report A report sponsored by the South Carolina Sea Grant Consortium and the State of South Carolina pursuant to National Oceanic and Atmospheric Administration Award No. NA10OAR4170073. Suggested citation: Cotti-Rausch, B.E., Majidzadeh, H., and DeVoe, M.R., eds., Stormwater Ponds in Coastal South Carolina: 2019 State of Knowledge Full Report. S.C. Sea Grant Consortium, Charleston, S.C. Cover photo by Grace Beahm Alford. SCSGC-T-20-02 Table of Contents Acknowledgements ...................................................................................................................iv Preface ........................................................................................................................................v Chapter 1 – A Pond Inventory for the Eight Coastal Counties of South Carolina .....................1 Chapter 2 – Environmental Factors and Design Features that Control Stormwater Transport and Contaminant Fate in Ponds ...............................................................................15 Chapter 3 – An Assessment of Nonpoint Source Pollution in Stormwater Pond Systems in Coastal South Carolina ..........................................................................................................41 Chapter 4 – The Ecological Function of South Carolina Stormwater Ponds within the Coastal Landscape ....................................................................................................................81 Chapter 5 – A Policy Lens of South Carolina Coastal Stormwater Management ..................103 Chapter 6 – An Economic Assessment of Coastal Stormwater Management.......................123 Chapter 7 – Communication Recommendations for Improved Stormwater Pond Maintenance in Coastal South Carolina ..................................................................................143 Chapter 8 – Synthesis of Our Current Understanding of Stormwater Ponds in Coastal South Carolina .........................................................................................................................159 Glossary of Acronyms .............................................................................................................185 Participating Institutions ACKNOWLEDGEMENTS We gratefully acknowledge all contributors who volunteered their time to provide comments and make contributions in their specific field of expertise to the work of the Stormwater Ponds Research and Management Collaborative, and ultimately to the synthesis of our current understanding of stormwater ponds in coastal South Carolina. A total of 32 individuals contributed to the preparation of this report (20 listed below and 12 anonymous, external reviewers): Jeff Adkins* Ed Oswald* NOAA Office for Coastal Management Charleston Trident Association of Realtors Lee Bundrick Richard Peterson, Ph.D. S.C. Sea Grant Consortium (former) Coastal Carolina University Currently at the Kiawah Conservancy Andrea Sassard David Fuss* S.C. Sea Grant Consortium (former) Horry County Stormwater Management Department Currently at the National Oceanic and Atmospheric (former) Administration Currently at the Indian River Land Trust Calvin Sawyer, Ph.D.* Shannon Hicks* Cooperative Extension, Clemson University S.C. Department of Health and Environmental Control Norm Shea* Dan Hitchcock, Ph.D. S.C. Department of Natural Resources Clemson University Allen Smith* Melody Hunt, Ph.D. Estate Management Services S.C. Sea Grant Consortium (former) Currently at the U.S. National Park Service Lisa Swanger Coastal Waccamaw Watershed Education Blaik Keppler Program ACE Basin National Estuarine Research Reserve April Turner* Michelle LaRocco S.C. Sea Grant Consortium North Inlet-Winyah Bay National Estuarine Research Reserve (former) John Weinstein, Ph.D. The Citadel Currently at Georgetown County, S.C. David Whitaker* Eric Larson* S.C. Department of Natural Resources (former) Beaufort County Stormwater Management Department Currently a member of the South Atlantic Fishery (former) Management Council Currently at EOM Operations Chris Marsh, Ph.D.* The LowCountry Institute *Stormwater Ponds Advisory Council members Special thanks to the S.C. Sea Grant Consortium Communications team: Joey Holleman, technical editor; Susan Ferris Hill, copy editor and proofreader; and Crystal Narayana, designer. EDITORS Bridget Cotti-Rausch, Ph.D. Coastal Environmental Quality Program Specialist (former), S.C. Sea Grant Consortium, Charleston, S.C. Currently an Environmental Protection Specialist, U.S. Environmental Protection Agency, Washington, D.C. Hamed Majidzadeh, Ph.D. Coastal Environmental Quality Program Specialist (former), S.C. Sea Grant Consortium, Charleston, S.C. Currently an Assistant Professor, Southern New Hampshire University, Manchester, NH M. Richard “Rick” DeVoe Executive Director, S.C. Sea Grant Consortium, Charleston, S.C. Stormwater Ponds in Coastal South Carolina: 2019 State of Knowledge Report iv ACKNOWLEDGEMENTS PREFACE The state of South Carolina has seen some of the most rapid coastal population growth rates and overall rates of urbanization in the nation. Its upward trend in population growth is expected to continue with a projected population in the coastal zone of over 1.5 million by the year 2030. The resulting urban and suburban growth in the region increases the amount of impervious surfaces (e.g., roofs, roads, parking lots) to support the associated development. As impervious surface area in a watershed increases so does the amount of stormwater runoff. In coastal South Carolina, the most common best management practice to control runoff is stormwater ponds. The S.C. Sea Grant Consortium, in collaboration with various stakeholders, identified ponds as a growing topic of concern throughout the eight coastal counties (Figure A.1). In October 2014, the Consortium initiated the S.C. Stormwater Ponds Research and Management Collaborative, an effort that gathered scientists and resource managers to investigate and address the challenges associated with these systems. The long-term vision of the Collaborative is to (1) satisfy the information needs and concerns of local communities, homeowners’ associations (HOAs), businesses, and industries surrounding pond design, maintenance, and management; (2) characterize coastal ponds to understand their functionality, durability, benefits, and costs; and (3) ultimately develop new and innovative engineering and Grand Strand Tri-County Lowcountry Figure A.1 South Carolina’s eight coastal counties with the three coastal regions designated as follows: (1) Grand Strand (Horry and Georgetown), (2) Tri-County (Berkeley, Charleston, and Dorchester), and (3) Lowcountry (Colleton, Beaufort, and Jasper). Stormwater Ponds in Coastal South Carolina: 2019 State of Knowledge Report v construction practices to ensure that current and future ponds function efficiently without negative ecological impacts or economic costs due to inadequate maintenance. What follows is the Collaborative’s initial product, a scientific state-of-knowledge report on stormwater ponds in coastal South Carolina organized in eight chapters. This report presents an inventory of existing ponds, a comprehensive literature review and gap analysis, and recommendations for research, outreach, and management. Twenty researchers from Consortium member institutions collaborated on this project, which was funded by the State of South Carolina and the National Sea Grant College Program. Each project team worked to ensure that any information on ponds from coastal South Carolina was included in the report. When coast-specific data were lacking on a given topic, studies from other regions or states were incorporated, as appropriate. The project was guided by the Stormwater Ponds Advisory Council (SPAC) comprised of regulatory agents, private sector representatives, and nonprofits. To satisfy the informational needs of our diverse stakeholder groups, we produced a series of products to convey the information gathered by our project teams. This technical report was written for the following audiences: researchers, the stormwater management community, and local and state decision-makers. To share this report with nontechnical groups, specifically individual property owners and HOAs, the Consortium will produce a pamphlet and booklet series written for general audiences. The results of this initial work by the Collaborative provide the foundation for the generation of additional science- based information, which fills critical information gaps to address key management and policy questions and provides for more efficient and cost-effective stormwater pond retrofits and design for the future. An executive summary of this report on stormwater ponds in coastal South Carolina is available on the S.C. Sea Grant Consortium’s website at www.scseagrant.org/spsok. Stormwater Ponds in Coastal South Carolina: 2019 State of Knowledge Report vi CHAPTER 1 – A POND INVENTORY FOR THE EIGHT COASTAL COUNTIES OF SOUTH CAROLINA Authors Erik M. Smith, Ph.D. Belle W. Baruch Institute for Marine and Coastal Sciences, University of South Carolina North Inlet-Winyah Bay National Estuarine Research Reserve Denise M. Sanger, Ph.D. Marine Resources Research Institute, S.C. Department of Natural Resources ACE Basin National Estuarine Research Reserve