Sediments are the substance of various and natural derivation. Erosion is the process displacement of this sediment by natural forces such as water, wind, gravity or ice. Sedimentation is when this is broken down into a form that flows from its sources to be deposited in various other places such as the coastline, in sediment stores or sinks. The natural origin of sediments that flows into the sea are rocks, soil and decomposed animal and plant life. This natural sediment movement is essential for the development and maintenance of home environments, swampland, partly enclosed areas of sea-water (lagoons), estuaries, coral reefs, mangrove forests, dunes and sand barriers.
Human activities are sometimes responsible for modification in the cycle of erosion and sedimentation as well as change the course of rivers and the number of sediments that is carried into the sea. Besides erosion of rocks and cliffs, sediments are also created by currents that bring in substances from the seabed, and they are deposited and becomes a landform or is stored on offshore ledges. On the other hand, it flows with the water and either rest in deeper waters some distance away from the embankments. Some sediment is termed as Clastic sediments which are from the rock being eroded. This is of many different sizes from fine clay to sand, gravel, shingle, stones and stands to the size of boulders. Biogenic sediments are the shells and skeletons of marine creatures.
Human activities that affect changes in sediment flow and deposits are generally related to agriculture, cutting of forests, urbanization, and mining. Another important reason for the change in sediment patterns is because of construction of huge tanks or lakes for storing water, dams, and causeways, dredging of massive irrigation schemes Changes in erosion patterns and the effects that this will have will basically depend on whether the quantity of salt is increased or decreases. In both situations, different physical effects are evident regarding water quality, the chemical relation between cause and effect and the well-being of the marine life
Mostly the effects of sedimentation are restricted locally, but sometimes these strong effects cross international boundaries because currents near the shore carry silt across. Increased sedimentation results in suffocating of fish and other forms of sea life, and in some instances completely covering up corals, mangroves and seagrass beds, reduces the amount of sunlight which penetrates resulting in limiting the production of a photosynthetic organism of a group that lives mainly in water and includes the seaweeds (algae) and other forms of underwater vegetation, it hurts fish by grating and flushing out their gills.