Road network analyses elucidate hidden costs of road flooding under accelerating sea level rise

Introduction: As sea level rises and coastal communities simultaneously grow, road flooding has the potential to significantly disrupt travel along road networks and make houses, businesses, and critical facilities difficult to reach. The impacts of tidal and storm surge flooding on roadways present challenging social and economic considerations for all coastal jurisdictions. Maintenance, public and private accessibility, evacuation routes, emergency services are just a few of the common themes local governments are beginning to address for low-lying roadways currently known to flood. Continuation of these services allows a community to thrive, to maintain or increase its tax base, and to ensure the safety and well-being of its citizenry. Methods: A traditional approach to analyzing road flood overlays flooding areas on roadways and focuses only on impacts within the actual zone of inundation. However, road flooding can also cut-off access to non-flooded roads and properties, closing the transportation corridor into or out of their downstream dwelling/service areas and other areas that may be impacted. In this study, we examined changing road inaccessibility under accelerating sea level rise for urban and rural localities. Results: Inaccessibility of roads and properties increased nearly twice as much as would be suggested by the length of flooded roads. Overall vulnerability of a locality was primarily dependent on its elevation; however, the redundancy of the road network appears to affect the rate at which properties became inaccessible. Areas with complex and redundant road networks-maintained access to coastal properties longer, suggesting increased resilience in the near term. Discussion: Road inaccessibility will impact property values and emergency response times but understanding the connection between flooding areas and inaccessible properties allows prioritization of road upgrades, improving overall coastal resilience

Expanding The Use Of Natural And Nature-Based Infrastructure To Enhance Coastal Resiliency

The vulnerability of coastal communities and the growing risks of coastal infrastructure continue largely due to past and ongoing patterns of development in high risk areas. This project is focused on increasing the use of natural and nature-based features (NNBFs) to increase resilience of coastal communities to flooding caused by extreme weather events

Prioritizing the protection and creation of natural and naturebased features for coastal resilience using a GIS-based ranking framework – an exportable approach

Increasing the preservation and creation of natural and nature-based features (NNBF), like wetlands, living shorelines, beaches, dunes and other natural features to improve community resilience in the face of increasing coastal flooding may be achieved by highlighting the locally relevant benefits that these features can provide. Here we present a novel application of the least-cost geospatial modeling approach to generate inundation pathways that highlight landscape connections between NNBF and vulnerable infrastructure. Inundation pathways are then used to inform a ranking framework that assesses NNBF based on their provision of benefits and services to vulnerable infrastructure and for the broader community including 1) the flooding mitigation potential of NNBF, 2) the relative impact of those NNBF on local infrastructure, and 3) co-benefits for the broader community linked to incentive programs like nutrient reduction crediting and the Federal Emergency Management Agency’s Community Rating System. Inundation pathways are also used to identify locations lacking in benefits from NNBF as target areas for NNBF restoration or creation. This approach, applied here for coastal Virginia, with project outputs available via an interactive map viewer1, can be customized for application in any community to identify high-priority NNBF that are particularly beneficial for preservation and to identify target areas for new or restored features

New Guidance to Build Resiliency and Mitigate for Sea Level Rise as Elements of the Chesapeake Bay Preservation Act

The Center for Coastal Resources Management (CCRM), Virginia Institute of Marine Science (VIMS), worked in collaboration with the Virginia Department of Environmental Quality (DEQ) and the Virginia Coastal Policy Center (VCPC) to develop guidance to inform the implementation of Chesapeake Bay Preservation Act (CBPA) regulations promulgated in 2021. The 2021 regulations added provisions to require local governments to consider climate changes, specifically flooding, sea level rise and storms, and the preservation of mature trees in the administration of the CBPA program. Specifically, CCRM developed analytical data using criteria specified in the CBPA regulations, of the National Oceanic and Atmospheric Administration (NOAA) intermediate high sea level rise curve for the year 2050, to project future shoreline and Resource Protection Area (RPA) features

Summary Tables: 2018 New Kent County, Virginia Shoreline Inventory

The Shoreline Inventory Summary Tables quantify observed conditions based on river systems, such as the combined length of linear features (e.g. shoreline miles surveyed, miles of bulkhead and revetment), the total number of point features (e.g. docks, boathouses, boat ramps) & total acres of polygon features (tidal marshes)

New Kent County, Virginia - Shoreline Inventory Report: Methods and Guidelines

The 2018 Inventory for New Kent County was generated using on-screen, digitizing techniques in ArcGIS® -ArcMap v10.4.1 while viewing conditions observed in Bing high resolution oblique imagery, Google Earth, and 2017 imagery from the Virginia Base Mapping Program (VBMP). Four GIS shapefiles are developed. The first describes land use and bank conditions (New_Kent_lubc_2018). The second portrays the presence of beaches (New_Kent_beaches_2018). The third reports shoreline structures that are described as arcs or lines(e.g. riprap)(New_Kent_sstru_2018). The final shapefile includes all structures that are represented as points(e.g. piers)(New_Kent_astru_2018).The metadata file accompanies the shapefiles and defines attribute accuracy, data development, and any use restrictions that pertain to data

Summary Tables: 2018 Caroline County, Virginia Shoreline Inventory

The Shoreline Inventory Summary Tables quantify observed conditions based on river systems, such as the combined length of linear features (e.g. shoreline miles surveyed, miles of bulkhead and revetment), the total number of point features (e.g. docks, boathouses, boat ramps) & total acres of polygon features (tidal marshes)

Strategy development to enhance the conservation and adaptation of Virginia coastal wetlands under climate change

Project activities addressed four priority elements in Virginia’s approved state wetlands plan. The existing monitoring and assessment strategy will be strengthened through incorporation of new data on the habitat function of existing and newly migrated marsh. Field surveys (information acquisition) will enhance existing understanding of marsh habitat function under sea level rise; and together with a water quality potential assessment, will support the refinement of an existing, EPA funded, marsh vulnerability analysis for conservation planning. Web-based tools for planners and managers (e.g., WetCAT) will be extended to incorporate information useful in planning wetland protection

Summary Tables: 2018 Essex County, Virginia Shoreline Inventory Report

The Shoreline Inventory Summary Tables quantify observed conditions based on river systems, such as the combined length of linear features (e.g. shoreline miles surveyed, miles of bulkhead and revetment), the total number of point features (e.g. docks, boathouses, boat ramps) & total acres of polygon features (tidal marshes)