AN ANALYSIS OF THE VOLUMETRIC GROWTH RATE OF THE SOUTHERN RECURVED-SPIT COMPLEX OF ASSATEAGUE ISLAND, VA FROM 1852 TO 2017

Assateague Island, MD-VA is a wave-dominated barrier island that is actively growing by lateral spit extension. A total of 17 historical nautical charts and NOAA T-Sheets at approximately decadal intervals from 1852 to 2017 were analyzed for this study. Historical maps and charts were georeferenced in order to digitize depth soundings and former shorelines. Areas of erosion and deposition between each map interval were identified to calculate a volumetric net change along the southern recurved-spit complex of the barrier island. Results indicate that the southern recurved-spit complex of Assateague Island has grown by 1.5 x 10⁷ m³ since 1852, with an average deposition rate of 9.0 x 10⁴ m³yr^-1. The only two time intervals that experienced net volume loss along the southern recurved-spit complex of Assateague Island were from 1855 to 1862 (2.7 x 10⁵ m³ net loss) and 1892 to 1901 (1.5 x 10⁶ m³ net loss). Additionally, a cyclic pattern of spikes of positive net change in the southern recurved spit of Assateague Island were identified. These peaks occurred in 1892, 1911, 1949, 1980, and 2017; suggesting that on average, a sharp increase in net volumetric change occurs every 31 years. The sharpest increase in net volumetric change within the study period was observed between 2006 and 2017, where the southern recurved-spit complex of Assateague Island grew by 6.1 x 10⁶ m³. The volume increase between 2006 and 2017 correlates with the start of semi-annual beach replenishment efforts along the vulnerable northern segment of Assateague Island in 2004. Overall, since 1852, the southern recurved-spit complex of Assateague Island has experienced a relatively constant cumulative barrier island volumetric growth rate, following the equation y = 74352x - 671903 with an R² of 0.91. Variables (i.e., storm activity, updrift tidal inlet activity, offshore bathymetry, and anthropogenic activity) and the magnitude of their influence that control the volumetric growth of the southern recurved-spit complex of Assateague Island are still unclear and are the focus of future research efforts.