Increased Land Subsidence and Sea-Level Rise are Submerging Egypt’s Nile Delta Coastal Margin
Egypt’s Nile delta, only ~1 m above mean sea level at the Mediterranean coast, is subject to uneven rates of submergence. This is a response to several factors leading to increasing land lowering (subsidence) of the northern delta and adjacent seafloor, plus an accelerating rise in eustatic (world) sea level in the Mediterranean. An average eustatic sea-level rise of ~3 mm/yr represents only ~26% to 45% of total relative sea-level rise measured along this margin. Three factors leading to subsidence are neotectonic lowering, compaction of Holocene sequences, and diminished sediment replenishment by much reduced Nile flow to Egypt’s coast. Subsidence accounts for variable average land lowering of ~3.7 mm/yr of section in the NW delta, ~7.7 mm/yr in the N delta, and ~8.4 mm/yr in the NE delta, based on compaction rates of strata thicknesses that decrease down-core between top and base of Holocene sections in 85 drill cores distributed along the delta margin. Among present critical challenges are marked reduction of Nile water and sediment below the High Aswan Dam that can now reach the delta coast. It is expected that problems of fresh water and energy poverty in the lower Nile Basin are likely to be seriously exacerbated in years ahead by construction of Ethiopia’s Grand Renaissance Dam (GERD). Completion of this, the biggest hydroelectric structure in Africa, is this year. Egypt, the Sudan, and Ethiopia must resolve the looming crisis of diminished Blue Nile water and sediment distribution to the lower Nile Basin and Egypt’s delta margin.
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Manuscript received 13 July 2016; Revised manuscript received 29 Oct. 2016; Manuscript accepted 17 Nov. 2016; Posted online 14 Feb. 2017