CHANGES IN GEOMORPHIC RESPONSE OF PARRAMORE ISLAND, VIRGINIA FROM 1871 TO 2000

Repetitive surveys of shoreline position provide the primary data source for determining shoreline behavior and quantifying rates of erosion and accretion. Using National Ocean Service (NOS) Topographic Sheets (T-Sheets), large-scale aerial photography, and GPS shoreline surveys, historical shoreline positions were compiled for Parramore Island, Virginia for the years 1871, 1959/62, 1980, 1998, 1999, and 2000. Parramore Island is undeveloped and is one of twelve barrier islands that characterize Virginia's Eastern Shore along the southern Delmarva Peninsula.

With a spring tidal range of 1.35 m (low mesotidal), Parramore Island has a classic "drumstick-shape" with large ebb-tidal deltas. The Atlantic Ocean shoreline of Parramore Island can be segmented into three zones. Zone 1, the high-profile, inlet-influenced northern end of the island, has been historically dynamic with rapidly changing shoreline positions but has shown a trend of retreat since 1980. Zone 2 is the north-central segment of Parramore Island and is dominated by the truncation of high-profile, tree-lined beach ridges. Historically, Zone 2 has been fairly stable but has been retreating since 1962 at ever increasing rates (-4.6 m/yr from 1959/62-1980, -8.3 m/yr from 1980-1998, and -9.0 m/yr from 1998-2000). This segment is an open-ocean shoreline and is currently characterized by numerous dead trees toppled across the upper portion of the foreshore. The southern half of Parramore Island is a low-profile, washover-dominated barrier and barrier spit delineated as Zone 3. This stretch of shoreline has retreated at high rates for the entire period of study but more rapid increases are documented since 1980 (-7.8 m/yr from 1871-1959/62, -6.4 m/yr from 1959/62-1980, -12.8 m/yr from 1980-1998, and -15.6 m/yr from 1998-2000).

Overall, the geomorphic response of the outer barrier island shoreline has changed from clockwise rotational instability to sustained erosion along most of the shoreline. Moreover, the rates of retreat tend to be accelerating. Four potentially inter-related factors may explain this change in shoreline behavior: 1) extension of the arc of erosion south of Fishing Point, 2) impact of the 1962 Ash Wednesday storm, 3) morphodynamics of the ebb-tidal delta at Wachapreague Inlet, and 4) relative sea-level rise.