________________________________________________________ QUANTIFICATION OF FLOOD EVENT FORCING AND THE IMPACT OF NATURAL WETLAND SYSTEMS: GREAT BAY BOULEVARD, OCEAN COUNTY, NEW JERSEY ________________________________________________________ US Army Corps of Engineers ® Institute for Water Resources This report was developed by the U.S. Army Corps of Engineers Institute for Water Resources in partnership with the U.S. Army Corps of Engineers Philadelphia District, Stockton University Coastal Research Center, and Barnegat Bay Partnership in accordance with a grant from the Federal Highway Administration (FHWA), Green Infrastructure Techniques for Coastal Highway Resilience, 2016-2017 Pilot Program. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of FHWA or the U.S. Department of Transportation. June 2018 Notice This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document. Quality Assurance Statement The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-HEP-18-069 4. Title and Subtitle 5. Report Date Quantification of Flood Event Forcing and the Impact of June 2018 Natural Wetland Systems: Great Bay Boulevard, Ocean County, 6. Performing Organization Code: New Jersey 7. Author(s) 8. Performing Organization Report No. Kim McKenna and Nick DiCosmo (Stockton University); Bari Greenfeld, Jeff Gebert, Heather Jensen (US Army Corps of Engineers) 9. Performing Organization Name and Address 10. Work Unit No. US Army Corps of Engineers, Institute for Water Resources 11. Contract or Grant No. 7701 Telegraph Road Alexandria, Virginia 22315 12. Sponsoring Agency Name and Address 13. Type of Report and Period Federal Highway Administration Pilot final report 1200 New Jersey Avenue, SE 14. Sponsoring Agency Washington, DC 20590 Code 15. Supplementary Notes This report documents a pilot project sponsored by the Federal Highway Administration (FHWA) in partnership with the US Army Corps of Engineers, Stockton University, and the Barnegat Bay Partnership. It is one of five pilot projects FHWA sponsored to assess the potential for natural infrastructure to protect specific locations along coastal roads and bridges. More information can be found at: https://www.fhwa.dot.gov/environment/sustainability/resilience/ongoing_and_current_research/green_infrastructure/ index.cfm 16. Abstract Great Bay Boulevard, located on the Tuckerton Peninsula in Ocean County, NJ, is a coastal roadway experiencing increased closures due to flood events. The project team explored the use of green infrastructure solutions that could simultaneously mitigate future roadway flooding and maintain marsh health over time. Thin layer placement of sediment could raise the marsh platform elevation in vulnerable locations along the road. A combination of oyster beds and native plants could be placed along the marsh edge to reduce overall wave energy at the site. 17. Key Words 18. Distribution Statement green infrastructure, wetlands, marsh, sea level No restrictions. rise, coastal, resilience, flooding 19. Security Classif. (of this report) 20. Security Classif. (of this 21. No. of Pages 22. Price Unclassified page) Unclassified 40 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized TABLE OF CONTENTS Executive Summary .................................................................................................. 1 Introduction ............................................................................................................... 4 Project Team .............................................................................................................. 5 Project Scope & Goals .............................................................................................. 6 Study Area ................................................................................................................. 7 Methods ................................................................................................................... 11 Results ..................................................................................................................... 16 Adaptation Options .................................................................................................. 23 Discussion................................................................................................................ 29 Summary of Key Findings ...................................................................................... 33 Takeaways & Next Steps ........................................................................................ 34 References ............................................................................................................... 36 Technical Appendices ............................................................................................. 40 LIST OF FIGURES & TABLES ES 1a/b. Examples of recommended adaptation options .................................................................3 Figure 1. View of Great Bay Boulevard during normal tidal conditions.........................................7 Figure 2. View of Great Bay Boulevard and flooded marsh one day after the passage of a northeast storm (January 24, 2017) .................................................................................7 Figure 3. View of a portion of Great Bay Boulevard and surrounding marsh lands .......................8 Figure 4. Coastal flooding of the Tuckerton Peninsula as shown in NJ FloodMapper ...................9 Figure 5. Site map and digital elevation model of Tuckerton Peninsula ...............................……10 Figure 6. Digital elevation model of the area showing all data collection sites ............................11 Figure 7. Marsh edge site showing R/V Osprey, piston core, and water level logger installation ..........................................................................................................12 Figure 8. CRC researchers using piston coring technique .............................................................14 Figure 9. Paddle-For-The-Edge volunteer collecting data at the project site ................................14 Figure 10. Map of marsh erosion and accretion ………………………………………………...18 Figure 11. Digital elevation model of the study site showing the proposed areas of TLP ............24 Figure 12. Example schematic of a living reef or wave attenuation device ..................................27 Figure 13. Marsh habitats of Tuckerton Peninsula (Able et al, 1999) ...........................................31 Table 1. SET sites and accretion rates from other Barnegat Bay locations ...................................17 _____________________________________________________________ EXECUTIVE SUMMARY _______________________________________________________________ In July 2016, the U.S. Army Corps of Engineers Institute for Water Resources (USACE-IWR) was awarded a Federal Highway Administration (FHWA) grant to analyze how green infrastructure, or nature-based infrastructure, can help protect Great Bay Boulevard in Ocean County, New Jersey from flooding due to severe storms and sea-level rise. This study builds upon coordination done by the Systems Approach to Geomorphic Engineering (SAGE) program, which convened stakeholders and identified locations within the Barnegat Bay region that could benefit from nature-based infrastructure. Great Bay Boulevard was one of those locations. Results from the study include an empirical understanding of what causes Great Bay Boulevard to flood, a survey of the surrounding salt marsh ecosystem, and two conceptual designs that intend to simultaneously reduce flood risks and improve ecosystem functions. The designs were evaluated relative to anticipated protection against future coastal impacts, implementation benefits and challenges, and lessons learned from prior marsh management studies and USACE green infrastructure projects in New Jersey. This project was led by a multidisciplinary team from the USACE Institute for Water Resources (IWR), USACE Philadelphia District, Stockton University Coastal Research Center (CRC), and Barnegat Bay Partnership (BBP), with the support of several other partners. Problem and Context New Jersey’s coastal bay shorelines are susceptible to flooding and storm surge. In 2012, Hurricane Sandy demonstrated this vulnerability by inundating many back-bay communities and causing significant structural damage. Communities within the Barnegat Bay watershed are still recovering five years after Sandy’s landfall. Since the historic storm, these communities have sought techniques for reducing their vulnerability by preparing for anticipated climate change and the