Over the past two decades, Eastern Shore coastal counties have experienced growth from Wallops Island to residential developments in Cape Charles (Bay Creek to Butlers Bluff). This growth also includes development along our tidal creeks. All the while, shorelines are experiencing erosion caused by natural forces such as barrier island migration, sea level rise, and coastal storms. High tides, Nor’easters and storm waves can erode and overtop structures which impacts costs not just for towns, but also land and aquaculture based farmers. Many coastal communities along the eastern seaboard that have found themselves in similar situations, have begun creating Beachfront Vulnerability Indexes (BVI) to assess community exposure and susceptibility to losses from storm surge and erosion.
BVI uses historical data (not just predictive models) to identify vulnerability to coastal hazards under present-day conditions at the parcel level. The BVI combines elevation (Lidar) data, long-term erosion rates (DHEC), number of dunes present (Dept of Health and Environmental Control(DHEC)), wave height (NOAA), tidal range (NOAA), a habitable structure’s proximity to an inlet (DHEC), and a habitable structure’s distance from the lines of jurisdiction (DHEC-OCRM setback line and baseline). Planners can use the BVI for long-term planning and can assess vulnerable areas along the beachfront.
Note: former Planner, Tom Bonadeo led an effort to obtain a robust set of Lidar data, which fundamentally changed the way we looked at elevation, and more importantly flood plain scenarios. This data set could continue to be very useful as the Town creates its own BVI.
The Eastern Shore is protected by a series of barrier islands and spits which act to separate the mainland coastal plain from the offshore continental shelf. According the USGS, the “major source of new sediment to the barrier beaches of the Southeastern United States is erosion of the adjacent headlands and beaches, whose sand generally migrates south as a result of longshore transport”. Over the past fifty years, there has been considerable movement, an actual deterioration of Eastern Shore barrier islands.
Barrier systems are inherently dynamic and in a constant state of change; the barrier islands appear to be changing into three different patterns. From Assateague south, all barrier islands are migrating towards the west. As sea level rises, the islands are “rolling over” as sand is eroded from the ocean side and re-deposited on the bay side during storms. The barrier islands of the north are retreating westward faster than the barrier islands at the southern edge of the Eastern Shore (Virginia Marine Resource Commission). Human activities can also have an effect, limiting regular sources of new sediment as well as the movement of sediment along the coastal plain. For some coastal regions, a large part of their sediment budget is supplied by rivers. Obstructions, such as dams can inhibit the natural transport of restorative sediments (see USACE Inventory of Dams:
As we are seeing on the Cape Charles beach this winter and spring, eroding coastal areas can perform replenishment by placing sand directly onto the beach (via dredging operations). Beach nourishment is not a permanent solution, yet for places that rely on tourism, such as Cape Charles, it can be an effective way to manage coastal deterioration.
Given the amount of factors that can have a detrimental effect on coastal communities, leveraging tools and technology to help manage and assess risk is an important element of the planning and future land use management policy. At the Nature Conservancy, the Coastal Resilience Program brings together an array of science, policy case study efforts to foster the development of ‘resilient coasts’; within this approach, nature is a substantial part of the solution. At its core, Coastal Resilience is a ‘decision support system that provides communities, planners, businesses and officials’ to identify and lower the ‘ecological and socio-economic risks of coastal hazards’, using nature-based solutions whenever possible.
One of the tools that is an integral part of Coastal Resilience is the Coastal Defense APP. Coastal Defense is a suite of geospatial applications that help identify nature-based solutions such as oyster reefs, tidal marshes, beach dunes, and seagrass, and then try to use this data to determine how effective they are in protecting coastal areas. From a purely technical standpoint, Coastal Defense uses the coastal protection model from the Natural Capital Project’s Marine Integrated Valuation of Environmental Services and Tradeoffs (InVEST) program. According to Nature Conservancy, “InVest has proven to be very effective in calculating the potential for nature-based solutions to reduce wave height and wave energy”. Given the brilliant work
An example of how Coastal Defense has been used, and how it might benefit the Eastern Shore, is in Alabama by the 100-1000 : Restore Coastal Alabama Partnership. This partnership is in the process of restoring 100 miles of oyster reef breakwaters and enhancing 1,000 acres of marsh and seagrass. The role of the Coastal Defense app is to help prioritize restoration sites, and determine where oyster reef restoration might work best.
Note: For more information on the research, models and data requirements for the Eastern Shore Coastal Defense App, contact Chris Bruce: cbruce@TNC.org or Gwynn Crichton: gcrichton@TNC.org
Scientific debates about the immediate causes of climate change and sea level rise, whether it is natural or cyclical, or from the effects of human activity, may continue for some time, yet the reality is they will both continue to put pressure on coastal regions like the Eastern Shore in the future. If sea level rise predictions of the Intergovernmental Panel on Climate Change are accurate, the Chesapeake Bay could disappear completely and become a salt water gulf comparable to the Gulf of Maine; the Eastern Shore would disappear below the Atlantic. From a planning and management point of view, this brings into question whether or not Northampton will be able to maintain residential and economic value in the future. In the near term, using tools such as GIS and Coastal Resilience to build data driven, statistically relevant Resilience and Beach Front Vulnerability Indexes could be a first, beneficial step in addressing this future change.