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Drowned Valley Coast Ecosystems

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.

Estuary Marsh

Estuary Marsh
Source: National Oceanic & Atmospheric Administration (NOAA)

Drowned Valley Coast Ecosystems

The low-energy conditions of estuaries, as opposed to those found on open coasts, allow for the deposition of fine-grained silts, muds, clays, and biogenic materials.