Assessment the impact of coastal protective structures on Damietta shoreline behaviour

Abstract Damietta Promontory is affected by multiple factors including meteorological parameters, human activities, and climate change. This research studies the impacts of various coastal protection structures like jetties, breakwaters, groins, and seawalls on shoreline behavior. Twelve Landsat imagery from 1980–2023 were used to detect shoreline changes, using Thresholding, Tasselled Cap Transformation, and Iso cluster approaches. Iso cluster was found to be the optimal digitization technique, with the lowest errors of 15% according to field observations. Using remote sensing data over a 43-year period, combined with Geographic Information System (GIS) and Digital Shoreline Analysis System (DSAS) tools Such as the Linear Regression Rate (LRR) that had a correlation value of 0.89 compared to field results, shoreline changes were analyzed in three distinct zones. First zone is Zone (A-1) at Damietta Port's eastern side, then Zone (A-2) with detached breakwaters at Ras El-Bar resort, and finally Zone (B), the Damietta Promontory's eastern coast. Results showed that the eastern beach of Damietta Port with a length of 1km shows significant accretion with an average rate of + 7.75 m yr −1 , while the coastline downdrift of certain protection structures, such as Y-groins, exhibits retreat. Also, the coastline behind detached breakwaters had a significant accretion rate of + 5 m yr −1 on average. So, detached breakwaters system showed an efficient performance and afforded stability at Ras El-Bar coast. In contrast, the eastern coast of Damietta Promontory retreated by an average rate of -45 m yr −1 on average. So, it is considered one of the major hazard zones at northeastern coast of Egypt. The predicted shoreline of 2030 shows a maximum retreat of 260 m downdrift the eastern seawall. Our predictions suggest the need for enhanced protective measures, particularly on eroding segments, to prevent future coastal risks.