HISTORICAL ANALYSIS OF A MULTIPLE INLET SYSTEM, SOUTHERN ASSATEAGUE ISLAND, MARYLAND: IMPLICATIONS FOR BARRIER-BACKBARRIER INTERACTION

The modern 60-km-long Assateague Island is representative of many retrograding wave-dominated coastal barriers. Its recent migration due to construction of the Ocean City jetties is well documented, however little is known about the morphology and dynamics of historical and relict tidal inlets. These openings in the barrier shoreline served as important conduits for tidal prism and sediment exchange between the Atlantic Ocean and Chincoteague Bay. Understanding the influence of tidal inlets and associated sand shoals on barrier and back-barrier morphodynamics is a key step in assessing the response of minimally developed barriers to external forcings, such as storms and sea-level change. Storm impacts, such as the November 2009 extratropical storm, underscore the importance of alongshore variability in barrier morphology. A series of historical charts and aerial photography were used to constrain the distribution and activity periods of historical inlets. This study focuses on the former Green Run Inlet, located just north of the MD-VA border, to highlight a different dynamic state of the barrier with a multiple inlet system from that of today. Based on historical charts, this inlet may have been open in the 1700s, possibly coexisting with Sinepuxent Inlet (1750s-1832) and several ephemeral channels to the north, and the still active Chincoteague Inlet to the south. The Pope Bay Inlet, mentioned in local historical documents, was likely a shallower but still navigable channel several kilometers to the south. Green Run Inlet is not depicted on the available 1820-1840s charts, but was the dominant tidal inlet along the barrier by the early 1860s, reaching a channel width of approximately 370 m in 1866, and closing by 1880. Assuming an average depth of 3 m, the 1866 tidal prism for this inlet may have reached approximately 1.5 x 10⁷ m³, which is comparable to that of the present-day Ocean City Inlet. Whereas fringing back-barrier saltmarsh has undergone minor changes in the past 150 years, former inlet sites have added geomorphic and subsurface complexity to the barrier lithosome. Future work will employ high-resolution geophysical surveys, sediment cores, and a combination of radiocarbon and optical dating to examine the geological legacy of former inlets and to constrain the chronology of major phases in their evolution.