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
Yangtze River Delta empires in China and each one had its own capital. The delta is one of the most densely populated regions on earth, and includes one of the world's largest cities on its banks — Shanghai, with a density of . Because of the large population of the delta, and factories, farms, and other cities upriver, the World Wide Fund for Nature says the Yangtze Delta is the biggest cause of marine pollution in the Pacific Ocean. Most of the people in this region speak Wu Chinese (sometimes called Shanghainese, although Shanghainese is actually one of the dialects within the Wu