Drowned valley coasts, also called estuaries, feature tidal flats and marshes along their sides and channels. In northern latitudes these take the form of salt marshes that are dominated by cordgrasses. Tidal range of a particular estuary affects the amount of marshes; wave-dominated estuaries that are shallow or have nearly filled may not have an open lagoon. Instead, they may be covered by extensive salt marshes crossed by tidal channels.
The shores of estuaries in low-energy environments, such as Chesapeake Bay and Delaware Bay, usually exhibit low-sloping and vegetated backshores and mud flats that are exposed at low tide.