Coastal Systems - Where the Sources of Sediment Originate from in a Coastal System

Sediment is brought into the coastal system in many ways.

Rivers can bring clastic sediments (weathered rock) into the coastal system. Subaerial processes such as freeze thaw weathering at the river’s source will have added material to the river channel and over time due to attrition and solution within the river the material reduces in size and is finally deposited when the river reaches the mouth. This sediment can then be moved by littoral (longshore) drift along the coast and is integral in the formation of depositional coastal landforms.

Sediment also comes from mass movement of the cliffs along the coastline. At high tide, wave energy may attack the cliffs, eroding material, noticeably by the processes of abrasion, hydraulic action and quarrying and this material may then be moved into the marine current zone by wave backwash across beaches to be carried away and deposited elsewhere.

Sediment can also be carried towards the coastline by onshore currents excavating sea floor stores of sediment under high energy conditions and moving it towards a shoreline.

Biogenic sediments from dead sea creatures (often shell and skeletal fragments) also contribute to the sediment load.