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
Saskatchewan River Delta during late stages of the Wisconsinan glacial epoch. These two components, commonly termed the "upper delta" and "lower delta", together occupy an area of approximately making the SRD one of the largest active inland delta in North America. The broad wetland tracts of the upper delta in Saskatchewan are sometimes referred to as the Cumberland Marshes. Approximately 5% of the delta surface has been drained for agricultural use following feasibility studies by the Prairie Farm Rehabilitation Administration in the 1950s. The SRD is fed mainly by the Saskatchewan River, whose drainage basin extends westward to the continental divide and includes