River delta slope offshore, waves will make river deltas smoother. Waves can also be responsible for carrying sediments away from the river delta, causing the delta to retreat. For deltas that form further upriver in an estuary, there are complex yet quantifiable linkages between winds, tides, river discharge, and delta water levels. Erosion is also an important control in tide-dominated deltas, such as the Ganges Delta, which may be mainly submarine, with prominent sandbars and ridges. This tends to produce a "dendritic" structure. Tidal deltas behave differently from a river- and wave-dominated deltas, which tend to have a few main distributaries. Once
Indus River Delta fan. Memon reports that the area of mangrove forests was 263,000 hectares in 1977 and in 1990. Both agree that they were sixth-largest mangrove forests in the world. Previously there had been eight species of mangroves, although only four now remain: "Aegiceras corniculatum", "Avicennia marina", "Ceriops tagal", and "Rhizophora mucronata". Among these "Avicennia marina" constitutes 99% of the mangrove population. As of 2007, the mangroves of the Indus delta are the largest desert climate mangrove forests in the world. "Arthrocnemum macrostachyum" is also found growing in the delta. The natural flow of water and fertile sediments from Indus river into