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 numerous minor creeks. The delta receives almost all of its water from the Indus river, which has an annual flow of approximately , and is accompanied by 400 million tonnes of silt. Since the 1940s, dams, barrages and irrigation works have been constructed on the river Indus. (In fact the World Bank has characterized the works as the "world's largest" and the Indus Basin Irrigation System as the "largest contiguous irrigation system developed over the past 140 years" anywhere in the world.) This has served to reduce the flow of water and by 1994, the annual flow of water into