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Georges River, in the southern suburbs of Sydney (Australia) 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.



The word ría comes from Galician and rias are present all along the Galician coast. It is related to the word río (river). As originally defined, this term was restricted to drowned river valleys cut parallel to the structure of the country rock that was at right angles to the coastline. However, the definition of ria was later expanded to other flooded river valleys regardless of the structure of the country rock. For a period of time, European geomorphologists[4] regarded rias to include any broad estuarine river mouth, including fjords, which are long, narrow inlets with steep sides or cliffs, created in a valley carved by glacial activity. However, the current and preferred usage of this term by geologist and geomorphologists restricts this term solely to drowned unglaciated river valleys and, thus, excludes fjords from being classified as rias.[1][2][3]


North America
South America


  1. ^ a b c Bird, E.C.F., 2008, Coastal Geomorphology: An Introduction, 2nd ed. John Wiley and Sons Ltd. West Sussex, England.

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