Assessing Sediment Transport Associated with Flood Erosion in Arid Areas Using InSAR Coherent Change Detection

Since the early 20
^th
century, the southern Mediterranean sandy coasts of North Africa (i.e., Tunisia, Libya, and Egypt) have experienced an increasing trend of rare extreme rainstorms, stressing the spatial variability of hydroclimatic conditions across the Mediterranean basin. Notably, Storm Daniel struck the eastern coast of Libya on September 10, 2023, resulting in deadly flash floods, principally after the collapse of two dams upstream of the city of Derna. Therefore, using Sentinel-1A C-band SAR images and the Coherent Change Detection method, we characterize and map the erosion and sediment load dynamics resulting from these flash floods over a 115 km × 40 km area, including Derna. Our findings highlight an increased vulnerability of coastal cities located at watershed outlets that need nature-based solutions to mitigate these risks.