Coastal Processes Coasts are places where land meets a large body of water, either a lake or the sea. Rivers and erosion of coastal lands bring sediments to the coast. Therefore, wave action is the primary agent that transports and deposits sediment along coastlines.
Wind can act on exposed beach sediments and create smaller-scale landforms on the beach.
Rivers carrying large amounts of sediments to the sea can deposit those sediments to from deltas, which protrude out from the shoreline. Variations in sea level can also modify shoreline geometry. High sea level drowns river valleys, causing the river channel to widen as it approaches the sea. Sea water and fresh water mix in these drowned river valleys. Such a water body is called an estuary .