Mud coasts
Very fine sediments such as silt and clay are normally kept in suspension near the coast. This is due to the small particle sizes combined with relative large water motions due to the waves. Mud coasts only occur if large amounts of fine particles are present or if the coast is protected from wave action. Protection from wave action is provided by particular coastal configurations such as in estuaries or lagoons. The coastal profiles of mud coasts are very flat (see Fig. 14 ); slopes can be as small as 1: 1000 or even flatter. Hence, the foreshore area, which is alternately wet and dry, is very wide.

Salt marsh
In protected areas, mud coasts may be covered with vegetation. These flat coastal areas are defined as salt marshes (see Fig. 16). The saline environment leads to a characteristic salt-tolerant vegetation. This and the importance of the wide marshes as feeding grounds for birds give the salt marsh its ecological importance.