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Why has the Nile delta retreated after sediment was trapped behind the Aswan High Dam?

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continental shelf The broad, gentle pitch of the continental shelf gives way to the relatively steep continental slope. The more gradual transition to the abyssal plain is a sediment-filled region called the continental rise. The continental shelf, slope, and rise are collectively called the continental margin.

The Nile delta has experienced significant retreat following the completion of the Aswan High Dam in 1970 primarily due to the loss of sediment supply.12

Under natural conditions, the Nile River transported approximately 40 million tons of nutrient-rich silt annually to the delta, which was essential for maintaining the coastline and land fertility. The dam now impounds these sediments within Lake Nasser, preventing them from reaching the river mouth.12

In the context of geology, the growth of a delta depends on a river delivering sediment to the shore at a rate and volume that exceeds the ability of marine processes to remove it. Because the dam has effectively cut off this clastic input, the shoreline has become a "battleground" where the energy of the Mediterranean Sea dominates. Without the constant replenishment of sediment to counteract wave action and currents, the delta is subject to coastal erosion, leading to its gradual retreat.342