ria

the followinfg is taken from my notes about rias and their formation, this should help you.

Submergant features
Rias
· Drowned river valleys. Fluvial erosion creates deep river valleys, flooded by rising sea levels. Flooding of main river valley and tributaries e.g. river Fal.
· After ice sheets melted, wide valleys flooded forming wide, tidal, sediment rich river mouths such as the Thames estuary.
· In hilly areas, such as in Cornwall, rias formed. Lower sections of the river valley flooded as sea level rose and picked out a pattern of former tributaries forming a tidal inlet.
· Rias become deeper as they enter the sea. Falmouth is built on the mouth of a ria, the river Fal that extends 18km inland.