Combined Effect of Anthropogenic and Natural Sources on Nile Delta Coast Erosion

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Akram Soliman, Bahaa Elsharnouby, Mohamed Elnaggar, Maysra Eltahan

Thursday 2 july 2015

17:15 - 17:30h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Morphodynamics of estuaries and coastal areas

Parallel session: 13A. Sediment - Coast

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The Nile Delta is located on the Egyptian Mediterranean coast and extends for about 240 km from Abu Qir headland at Alexandria on the west to Port Said at the east. Along the Nile delta of Egypt for thousands of years, the Nile River has carried vast quantities of sand derived from equatorial east Africa, displacing the delta coast seaward into the Mediterranean Sea. However, since the late nineteenth century there has been a prolonged period of decrease in discharge on the Nile, essentially caused by a dramatic decrease after the construction of the Aswan High Dam in the 1960s. Shoreline erosion has destroyed coastal roads, recreational facilities and beach resorts at Alexandria, Rashid and Baltim cities, Egypt. Kitchinar drain, which is located 5 km east of Baltim city, delivers about 18 m3/sec of water flow to Mediterranean sea. The west coast of Kitchener drain is protected by fourteen emerged detached breakwaters and nine emerged perpendicular groin which prevent the transported sediments. The shortage of sediment source for the east coastal side of the drain allow shoreline to be eroded under dynamic wave impact for five kilometer east of the drain. More than 103 beach profiles have been surveyed by CoRI since 2003 to 2013 to monitor coastal surf zone changes. From these extensive surveys, 76 profiles 100 meters spacing have been selected. Three scenarios have been numerically modeled for different human artificial interaction structures to protect this zone from erosion. These three scenarios are protecting the outfall using two main emerged Jetties. Scenario 1 includes 8 detached emerged breakwaters combined with 6 groins while scenario 2 includes submerged breakwater and 7 groins. Scenario 3 includes 15 eastern emerged groins and 4 intermediate groins. The three scenarios have been modeled numerically using finite element model (Mike 21 Coupled Model FM), which is based on two dimensional shallow water equation. Numerical models have been calibrated and validated by adjusting bed level changes at bed profiles and shorelines located in the eroded zone. Studies showed that, scenario 2 is the preferred scenario to protect shoreline from erosion with low currents speed (~.005 to .01 m/s), low wave heights(~0.1m) behind submerged breakwater, and allows water circulation or tidal currents to pass over submerged breakwaters.