Nile delta

• The river Nile has a length of 6650 kilometers and has a catchment area of over 3 million kilometers squared.
• The mean annual rainfall in the catchment is about 600 mm, yet the average discharge is less than 3000 m^3/s.
• The river Nile mostly originates in Ethiopia, the rest comes from central Africa.
• The suspended sediment load is

  • 30% clay
  • 40% silt
  • 30% fine sand
• The annual average sediment yield is 4.26 t/ha/year and the total is 91.3 million tonnes for the whole Blue Nile Basin in Ethiopia.
• The Nile Delta runs parallel to the Mediterranean coastline.
• 3 distinct subunits of the coastal plain can be recognized:

  • the foreshore plain - characterised by elongated ridges, alternating with salt marshes, lagoons and alluvial deposits in the depressions between them
  • the frontal plain - has scattered eroded limestone outcrops and clay deposits
  • the sandy zone - comprised of many different sand formations, such as sheets, dunes and hummocks.
• The delta begins to split into distributaries at Cairo, more than 160 kilometers inland.
• Before the constructions of the Aswan Dam in 1964, The Nile's annual flood covered much of the delta each year and deposited a thick layer of silty mud.
• Wave action in the Mediterranean redistributes the sediment at the front of the delta, the reworked sediment forms a series of curved barrier bars, which closes segments of the Mediterranean sea to form lagoons. These lagoons soon become filled with fine sediment.
• The prevalence of north-westerly winds enhances the constant eastward movement of water and sediment
• The prevailing winds leads to the waves coming from the west, northwest and north for 55 to 60 percent of the time. The resultant nearshore features include underwater sand bars
• Many beaches west of Abu Qir headland contain long crescentic bar systems. Parallel longshore bars exist along the delta extending from east of Abu Qir to Port Said.
• The parallel bar systems along the delta are generated by the dominant eastward movement of water and sediment. The crescentic bar systems are associated with rip currents and negligible longshore drift.
• Rates of deposition have exceeded rates of erosion for over 3000 years
• Since the building of the Aswan Dam, there has been a rapid reduction in the amount of sediment deposited, from 120 million tonnes/year to only trace amounts today.
• The building of the Aswan Dam has accelerated erosion rates and coastal retreat rates have been as high as 148 m/year.
• Rising sea levels in the Mediterranean of 1.2 mm/year have also contributed to higher erosion rates as deeper water produces larger waves with higher amounts of energy that can also reach further inland.