Drowned valley coasts, or estuaries, can be wave-dominated if they are characterized by high wave energy compared to tidal influence. At wave-dominated estuaries, waves cause sediment to move alongshore and onshore into the mouth of the estuary, forming sand bars or subaerial barriers and spits. The barriers prevent most of the wave energy from entering the central basin.
The low wave-energy conditions of these coasts allow for the deposition of fine-grained silts, muds, clays, and biogenic materials. Estuarine sediments are typically soft and tend to be deposited on smooth surfaces that limit turbulence of the moving water.