Simulating mitigation scenarios for natural and artificial inlets closure through validated morphodynamic models

Abstract

The coastline of the Nile Delta extends between Alexandria and Port Said and spans approximately 240 km. It experienced accelerated erosion since the construction of Aswan High Dam (AHD) where more than 1.2 billion EGP were spent to mitigate the imbalance in sediment transport patterns as AHD blocks most of the sediments reaching the Mediterranean coast. The current study investigates various combinations of interventions to mitigate the complex situation around natural and artificial tidal inlets namely Rosetta promontory and El-Burullus fishing harbor inlet. After various previous interventions in both sites, the problem of structures stability, inlets closure, and erosion in the nearby beaches still exists. The study will utilize already developed, calibrated and field validated morphodynamic models for the two areas of interest. Out of the past and present tested scenarios, the study comes up with the optimum combination of interventions at the two inlets. For Rosetta promontory, the third scenario (one-kilometer jetty in the western direction, a 0.4 kilometer one at the eastern direction, another three groins at the eastern direction, and two groins at the western direction) has the least net sedimentation volume at the inlet (2206.58 m3) and the least change in depth at the critical sections. On the other hand, the simulations indicated that SC3 (extension (90 m) of west jetty + 5 east 200 m groins + 2 west groins (200 m)) produced ideal results in terms of the El-Burullus harbor entrance siltation, the erosion in front of seawall and the accretion at the west of breakwater; However, it caused some slight erosion at the shoreline west of the breakwater. The successful concluded results of this study could be adopted with appropriate modifications for other Deltas worldwide.