Methodology for Monitoring Silting and the Coastline of Small Ports Using Sentinel-2 Images: The Case of Port Cap Djinet Algeria

Abstract

One of the ports most affected by the phenomenon of silting in Algeria is the port of Cap Djinet. In order to consider the monitoring of this port over a period of 8 years between 2015 and 2023, the twin Sentinel-2 A/B satellites were used. After image pre-processing, the bathymetry was estimated using the algorithm developed by Stumpf and extraction of the coastline was conducted using the normalized difference water index (NWDI). As part of this work, four bathymetric surveys were conducted in situ in four different periods, the results of which then correlated with those of the Stumpf model applied to satellite images. The results of the regression analysis are consistent and show good correlation coefficients (R2) between 0.67 and 0.80 and root-mean-square error (RMSE) values between 0.87 m and 1.32 m, except for images captured under turbid water conditions. The maximum accretion surface is 2.12 ha to the north of the port, estimated for the period from 2018 to 2019, and 1.78 ha to the south for 2015 to 2016. The maximum erosion surface is 2.37 ha to the north of the port for the period from 2017 to 2018 and 1.16 ha to the south from 2017 to 2018. Therefore, the amplitude of accretion and erosion is greater to the north of the port than to the south. The present study demonstrates the ability of Sentinel-2 satellites to monitor silting and coastline changes in the vicinity of this port, which could help to address the effects of climate change and human activities in order to protect the marine ecosystem.