Governments Plan for Development of Land Vulnerable to Rising Sea Level: Middle Peninsula, Virginia

From EPA report prepared by Virginia Institute for Marine Sciences (PDF 8.7 MB) and other experts

The Middle Peninsula Planning District includes the land between the York and Rappahannock rivers. The peninsula includes Mathews and Middlesex counties, which are along Chesapeake Bay. Gloucester County is between the York River and Mobjack Bay, with very little of the county actually on Chesapeake Bay. Gloucester is the most developed county, while the remainder of the Middle Peninsula consists of a mix of rural areas and seasonally occupied coastal homes.

Elevations

Gloucester County has between 13 and 33 square kilometers of dry land within 1 meter above the coastal wetlands. Most of that land is on the Guinea Neck. The long-established communities on this neck may be the most vulnerable to rising sea level along the Western Shore of Chesapeake Bay. Unlike the low-lying developed communities in the Hampton Roads area, Guinea Neck does not yet have an infrastructure designed to cope with rising water levels. (See Table 1.)

The vast majority of Mathews County is less than 6 meters above spring high water, as the elevation map shows. For the most part, the very low dry land in this county tends to be undeveloped forests lying just inland of the tidal wetlands. Its most vulnerable development is in the southernmost neck, between Horn Harbor and Mobjack Bay, approximately 1-1.5 meters above spring high water. The other counties have relatively little low land. In spite of its name, for example, Deltaville (Middlesex) is generally 4 meters above sea level and not immediately vulnerable to inundation.

Vulnerable Habitat

Like the marshes of Poquoson to the south, the marshes of the Guinea Neck and adjacent islands are not keeping pace with the current rates of sea-level rise. For more than three decades, scientists have documented their migration onto farms and forests.. Thus, the continued survival of these marshes depends on land-use and shore protection decisions.

Upstream from the Guinea Neck, sea-level rise is evident in the York River's tributaries, not because wetlands are converting to open water but because the composition of wetlands is changing. Along the Pamunkey and Mattaponi Rivers, dead trees reveal that tidal hardwood swamps are converting to brackish or freshwater marsh as the water level rises. Tidal hardwood swamps provide nesting sites for piscivorous (fish eating) species such as ospreys, bald eagles, and double-crested cormorants..

In Mathews County, Bethel Beach (a natural area preserve separating Winter Harbor from Chesapeake Bay) is currently migrating inland over an extensive salt marsh area. The beach is currently undergoing high erosion and is home to a population of the Northeastern beach tiger beetle (federally listed as threatened) and a nesting site for rare least terns, which scour shallow nests in the sand. In the overwash zone extending toward the marsh, a rare plant is present, the sea-beach knotweed (Polygonum glaucum) . The marsh is also one of few Chesapeake Bay nesting sites for northern harriers (Circus cyaneus), a hawk that is more commonly found in regions further north.. As long as the shore is able to migrate, these habitats will remain intact; but eventually, overwash and inundation of the marsh could reduce habitat populations.

Likelihood of Shore Protection

Our summary map and Table 2 show likelihood of shore protection for Virginia's Middle Peninsula, Gloucester County expects most developed areas to be protected. But the county's land use policies also have a strong conservation ethic. A large portion of the necks along Mobjack Bay has a conservation zoning that allows only low-density residential development "in a manner which protects natural resources in a sensitive environment." The intent is to preserve contiguous open spaces and protect the surrounding wetlands. The County also seeks to maintain coastal ecosystems important for crabbing and fishing, and planners view shore protection as unlikely. As a result, wetlands and beaches along Mobjack Bay are likely to be able to migrate inland as sea level rises.

Gloucester County also has a suburban country side zoning, which allows for low density residential development, including clustered sub-developments along part of the Guinea Neck and along the York River between Carter Creek and the Catlett islands. The higher densities and high quality homes make shore protection likely, though not certain. West of Gloucester Point, however, lands with the same density will almost certainly be protected, given the modest cost of protecting an area with high ground and moderate wave climate. Although most of the York River shores are very likely to be protected, a number of areas are off-limits to development. For example, the Catlett islands are part of the Chesapeake Bay National Estuarine Research Reserve in Virginia, managed as a conservation area.

Confidence in maps of the likelihood of shore protection is less for the remaining counties. Developed areas are viewed as likely - and in most cases very likely - to be protected; but prospects for future development are uncertain. Planners view development and shore protection as unlikely along the wetland shore of the upper York River.

Top of page

Governments Plan for Development of Most Land Vulnerable to Rising Sea (PDF, 7 pp., 1.3 MB, was originally published in Environmental Research Letters , Issue 3, Volume 4 (2009).