Applying geospatial technology in quantifying spatiotemporal shoreline dynamics along Marina El-Alamein Resort, Egypt.

Abstract

Human interventions along the northwestern Egyptian Mediterranean coast recently interrupted the stability of Marina El-Alamein shoreline and resulted in spit evolution. Considering Egypt's vision 2030 for developing the northwestern Egyptian coast, continuous up-to-date monitoring programs became essential to ensure sustainability. This study, for the first time, aimed at coupling geospatial technology with Digital Shoreline Analysis System (DSAS) tool in monitoring, analyzing, and quantifying the impacts of anthropogenic activities on the spatiotemporal shoreline dynamics over the last 3 decades (1987-2017) at Marina El-Alamein resort, Egypt. In addition, the study carried out a quantitative geometrical temporal analysis for the newly formed spit from 2015 to 2020. The study used transect- and area-based approaches in estimating the shoreline changes for long- and short-term changes. The former approach computed the change in both the shoreline displacement and the rate of shoreline change, whereas the latter quantified the magnitude of spatial changes in the total land area. Results of the current study revealed that during 1987-2017, Marina El-Alamein shoreline experienced very high accretion, with an average rate of 2.8 ± 4.73m/year (end-point rate) and 2.52 ± 4.10m/year (linear regression rate). Quantitatively, Jetties #1 and #3 trapped sand on their western sides for a maximum distance of 706.31m and 406.5m, respectively. On the other hand, the eastern side of the resort experienced erosion with a maximum distance of 92.78m. Regarding changes in the total area, Marina El-Alamein's coast gained 1.130km2 (0.038km2/year) land and lost about 0.1115km2 (0.004km2/year) of its total area throughout the last 3 decades. During 2015, the continuous progressive accretion along the western side of J#1 resulted in the evolution of sand spit east of the jetty. Results of the temporal analysis showed that the spit's length was about 0.236km during May 2015 and reached 1.44km in April 2020 with an increment of 510.5% in length. In addition, the spit's total surface area increased by 33.606km2 in 5years (6.7212km2/year). Both the length and the area of the evolving spit grow annually with 102.11% and 108%, respectively. If this progressive accretion along the evolving spit continued, the lagoon's first inlet would probably suffer sedimentation that could cause its closure and deteriorate the lagoon's water quality. The study recommends carrying out an environmental impact assessment study for the newly formed spit to lessen its negative impact on the opposite tidal inlet and the lagoon's water quality.