Nile delta: extreme case of sediment entrapment on a delta plain and consequent coastal land loss

Abstract

Accelerated erosion of Egypt's Nile delta coast during this century has generally been attributed to construction of two dams at Aswan, entrapment of sediment in Lake Nasser behind the High Dam, and effects of barrages and river control structures on River Nile deposition below Aswan. Also considered important are natural factors, including delta subsidence, rising sea level and strong coastal current processes. This study proposes that more influential in controlling coastal land loss is the near-complete entrapment of modern and reworked Nile sediment on the Nile delta plain. Sediment is primarily retained in an extremely dense network of irrigation and drain channels, and also in wetlands in the northern delta. The increased number of artificial canals, more than 10,000 km of waterway, is a response to Egypt's drive to augment its much-needed agricultural production by perennial irrigation. The drastically reduced amount of sediment now reaching the sea, discharged primarily from lagoon outlets and several canal mouths, is removed by strong, easterly-directed coastal and innermost shelf currents. The Nile delta is an extreme example of a depocenter which has been completely altered by man, from an active prograding delta to a locally eroding coastal plain.