Hydrodynamic Simulation of Rip Currents Along Al-Nakheel Beach, Alexandria, Egypt: Case Study

Al-Nakheel beach is located northwest of Alexandria city, Egypt, along the Mediterranean coast. During the period from 1998 to 2003, seven detached breakwaters were constructed along Al-Nakheel beach to create a sheltered area for swimming. Unfortunately, the structures amplify rip currents, shoreline accretions, and erosions. The aim of this research is to track the variations of the rip currents within the study area and show the effects of the breakwaters on the shoreline. The research is based on the hydrodynamic and morphological data of the study area and uses the Delft3D hydrodynamical model combined with other data analysis tools to serve the model input. The data include measured sea-level observations in 2013, the ERA-interim wave datasets from 2015 to 2018 and wind data in 2018, bed morphologies, and Google Earth satellite images from 2010 to 2020. The model is calibrated on the basis of the available current measurements within the nearshore zone. Results show that the shoreline eroded at an average rate of about 0.9 m/yr. Moreover, pairs of vortices are formed behind the breakwaters with an average current velocity of 0.6 m/s. The predominant northwest waves induce rip currents on the leeside of the structures with velocities reaching 1.2 m/s, associated with the rip pulsation that extends offshore. The problem solution decision recommends the removal of the sand deposition on the leeside of the breakwaters by an average amount of 100 000 m 3 /yr and the fencing of the safe area for swimming by a floating fence of 1 000 m length and 65 m average width.