Estuaries and Salt Marshes

Abstract

Estuaries form where rivers flow into the sea. Their shape varies with the river flow, tidal range, the local coastline and so on. Estuaries of large rivers modify the coastline and sublittoral topography for many kilometres around by deposition and erosion of bottom sediments. For example, the Mississippi River is very broad and slow, carries a large sediment load of about 10¹¹ kg per year, and has a delta of land at its mouth 10 to 20 km wide. The river sediment can be traced from the delta across 120 km of continental shelf which deepens slowly to about 50 m, and then down the continental slope to the abyssal plains.