Ria

This article is about the coastal landform. For the given name, see Ria (given name). For other uses, see RIA (disambiguation).

Port Jackson, also referred to as Sydney Harbour, is a ria, or drowned river valley. The deeply indented shape of the ria reflects the dendritic pattern of drainage that existed before the rise in sea level that flooded the valley.

A ria (/ˈriːə/; Galician: ría, feminine noun derived from río, 'river') is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea.