Historical Shoreline Mapping: Application of the Digital Shoreline Analysis System to the Evolution of Worthing Beach, Barbados, Following Hurricanes Allen (1980) and Ivan (2004)

This paper examines the application of the Digital Shoreline Analysis System (DSAS), developed by the U.S. Geological Survey, to a test site at Worthing Beach, Barbados. The system calculates shoreline rates-of-change statistics from historical shoreline positions by casting transects perpendicular to a common baseline and observing where each transect intersects with beach width. DSAS was applied using four historical aerial photographs (1973, 1982, 1991, and 2004) to project its 50 year trend (1973-2023). Following the impact of Hurricane Allen (1980), Worthing Beach, contrary to expectations, exhibited a rapid accretion rate of 7.0 m/y. Subsequently, the passage of Hurricane Ivan (2004) led to the removal of approximately 110 m of shoreline while the hurricane impacted the island. The linear methodology used by DSAS, however, projected continued accretion over the central spur up to the base of the coral rubble reef within the nearshore, which was in contrast to the actual shoreline trend. It was hypothesized that both rapid accretion and erosion were initiated by changes in the height of the coral rubble reef introduced by each of the hurricanes, respectively. The statistical projections were used to assess the accuracy of the computed shoreline positions prior to the implementation of engineering works in 2006 by the Barbados Coastal Zone Management Unit, since erosion continued to threaten infrastructure along the back beach long after Hurricane Ivan (2004). It was concluded that it is essential to identify the underlying causes of accretion and erosion to assist in designing any engineering interventions.