The Nile Delta is built of sands carried to Egypt's Mediterranean coast by the Nile River, primarily since the end of the last ice age. Dams along theriver and entrapment of sediment in a vast network of irrigation canals have led to a dramatic decrease in the flow of water and sediment to the delta'sedge. At several points along the coast, the delta is now receding. The Damietta Promontory has eroded dramatically as waves and currents havestripped its sands faster than the river can replenish them. While there are local areas of accretion such as the Damietta Spit, on balance the delta is shrinking. Prior to the construction of the Aswan High Dam, fresh water from annual floods influenced salinity and circulation patterns up to 80 kmoffshore from the delta. In contrast, current discharge patterns allow salt water from the Mediterranean to reach dams up to 26 km inland. Diminished freshwater and sediment delivery to the delta also affects the ecology of coastal lagoons, soil fertility, and salinisation of irrigated land. Coastalprotection structures, regulation of irrigation, and increased groundwater exploitation may mitigate the delta's decline, but the current rate of populationgrowth threatens to outstrip these measures. Images show the erosion of the Damietta Promontory, formed by one of the two principle outlets of the Nile River as well as the eastern migration ofthe sediments. One study has found that the delta is sinking by 5 mm per year and attributes the main causes of the sinking to the dams along theriver that trapped river sediments, and rising sea levels due to global warming. Since the closing of the Aswan High Dam in 1964, the forces of erosionhave outstripped the balancing effect of sediment deposition. Seawalls are constructed in some areas to stop the Nile delta being eroded by the seaand regulated irrigation and increased groundwater exploitation may also help to reduce the delta's decline. On the other hand, the population isgrowing in the region, increasing pressure on the delta and making saving the delta a greater challenge.