A ria 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.
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 satellite view of Galicia
Ria of San Vicente de la Barquera in Cantabria, Spain
Ria of Rijeka Dubrovačka in Dubrovnik, Croatia
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.
Río de la Plata estuary
New York–New Jersey Harbor Estuary
River Exe estuary
Estuary mouth located in Darwin, Northern Territory, Australia
