The Nile

Landscape and Geomorphology

The Nile Delta was formed by sedimentary processes between the Miocene and the present. The river is built up by the alluvium brought in by the old seven active tributaries of the Nile. These tributaries then silted up and were replaced by today's Damietta and Rosetta tributaries. The Nile Delta is a typical wave-dominated delta, characterised by a shore that consists of sandy arcuate beaches. These beaches are backed by coastal flats followed by coastal dunes and three lagoons (Coastal Research Institute, 2009).

Urban development

The Nile Delta is one of the earliest recognized deltaic systems in the world. The delta has been inhabited by people since ancient times and cities came into being early on. This is not surprising since most of Egypt is desert. Egypt has one of the largest and fastest growing populations in the world, 96% of whom live in the Nile Delta. This uneven distribution of the population within the country has caused major socio-economic problems. Between 1992 and 2015, 74.600 hectares of fertile agricultural land were lost to urbanisation. However, a lot of uncultivated land has also been converted into farmland, as much as 206.100 hectares. In a "business as usual" model, another 87.000 hectares of agricultural land will be lost to urbanisation by 2030. This poses a threat to the sustainability of the agricultural sector and food security in Egypt (Radwan et al., 2019).

Sediments

Deltas undergo alternating build-up and breakdown phases due to fundamental changes in the relative influence of sediment input from rivers and redistribution by coastal marine processes. During the past 7000 years, the Nile delta has been in a general build-up phase. In the last 150 years, however, the Nile has moved into a destruction phase, triggered by human influences. Projects such as water regulation upset the balance between sediment supply, erosive effects of coastal processes and land subsidence. This former depocentre has changed to the extent that it is no longer a functioning delta, but rather a subsiding and eroding coastal plain (Stanley & Warne, 1998). The accelerated erosion of the Egyptian coast in the Nile Delta is largely caused by the extremely reduced supply of sediment from the Nile. This change in sediment supply is due to a number of different (mainly human) factors, namely, the construction of two dams at Aswan, the entrapment of sediment in Lake Nasser behind the high dam, and the effects of weirs and river control works on the deposition of the Nile below Aswan. There are also a number of natural factors causing the accelerated erosion. For example, issues such as sea level rise and strong coastal current processes are considered important. In the current Nile delta, sediment is mainly retained in an extremely dense network of irrigation and drainage channels, partly also in the wetlands in the northern delta. The huge increase in artificial canals (over 10,000km of waterways) within the delta stems from Egypt's desire to increase agricultural production, through perpetual irrigation. The result is a drastically reduced amount of sediment reaching the sea and degradation of the coast (Stanley, 1996).

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