3.3 Sediment Sources, Cells and Budgets Flashcards
Outline the 6 main sources of sediment.
- rivers
- cliff erosion
- longshore drift
- wind
- glaciers
- offshore
Outline rivers as a source of sediment.
Sediment is transported in river, and often accounts for the vast majority of coastal sediment, especially in high-rainfall environments where active river mouth erosion occurs.
This sediment will be deposited in rive mouths and estuaries - where it will be reworked by waves, tides and currents.
Outline cliff erosion as a source of sediment.
This can be v important locally in areas of relatively soft or unconsolidated cliffs.
The toll cliffs along the Holderness coast comprise sand and clay, and rates of erosion can be as high as 10m per year. However, in Cornwall, the tough igneous rocks erode at very slow rates.
Outline longshore drift as a source of sediment.
Sediment is transported from one stretch of coastline (output) to another stretch (input).
Outline wind as a source of sediment.
In glacial, or hot arid environments, wind blown sand can be deposited in coastal regions.
Sand dunes are semi dynamic features at the coast that represent but sinks and sources of sand.
Outline glaciers as sources of sediment.
In parts of the world eg Alaska, ice sheets calve (chunks of ice breaking off a glacier) into the sea, depositing sediment trapped within the ice.
Outline offshore as a source of sediment.
Sediment from offshore can be transferred into the coastal (littoral) zone by waves, tides and currents.
In the U.K., sea levels rose at the end of the last glacial period, resulting in a considerable amount of coarse sediment being bulldozed onto the south coast of England to form landforms eg barrier beaches.
Define sediment cell.
A stretch of coastline, usually boarded by two prominent headlands, where movement of sediment is more or less contained.
Outline inputs of a sediment cell.
Inputs are primarily derived from the river, coastal erosion and offshore sources eg bars or banks.
Outline transfers of a sediment cell.
Longshore drugs. Onshore and offshore processes eg rip tides.
Outline stores (sinks) in a sediment cell.
The beach, sand dunes and offshore deposits eg bands and bars.
How many sediment cells are there in the UK?
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Outline a few of the impacts of coastal protection on sediment budgets and the sediment cell.
- depleted beaches lead to steeper slopes so waves break closer to the coast.
- deflected down drift erosion leads to net sediment losses and transport corridor.
