Coasts- Coastal Sediment

Question 1

What is a sediment cell?

Answer 1

• a stretch if coastline within which sediment movement is more or less contained
• generally bordered by two large headlands/deep water and contain inputs, transfers and stores of sediment
• in total there are 11 cells around the UK- which are further divided into sub cells

Question 2

Examples of transfers/flows in a sediment cell

Answer 2

• Longshore Drift
• wind
• currents

Question 3

Examples of sinks/stores in a sediment cell

Answer 3

• beaches
• sand dunes
• offshore bars

Question 4

Sediment source- rivers

Answer 4

• sediment transported into rivers accounts for the majority of coastal sediment
• especially in high rainfall environments where active river erosion occurs
• sediment will be deposited in river mounts and estuaries where it will be reworked by waves, tides and currents

Question 5

Sediment source- cliff erosion

Answer 5

• important locally in areas of soft or unconsolidated rocks
• cliffs along Holderness coast comprised of sand and clay- rates of erosion as high as 10m per year
• contrasts the igneous granite cliffs in Cornwall with low erosion rates

Question 6

Sediment source- offshore sediment

Answer 6

• sediment from offshore can be transferred into the coastal zone by waves, tides and currents
• in the UK, sea levels rose at the end of the last glacial period resulting in coarse sediment building up on the SE coast of England
• form landforms such as barrier beaches
• storm surges can be responsible for inputs of sediment

Question 7

Sediment source- wind

Answer 7

• in glacial/hot environments wind-blown sand can be deposited in coastal regions
• sand dunes are semi-dynamic features at the coast which represent both accumulation of sediment and potential sources

Question 8

Flamborough Head sub-cell

Answer 8

• located on east coast of England

- can be further divided into two parts- north and south of the Humber estuary

Question 9

Implications of sediment cells

Answer 9

• amount of sediment gained from sources and lost to the sinks can be quantified
• a sediment budget can be made to highlight variations in the amount of source and sink sediments
• useful for assessing causes of coastal change eg. the effect of artificial structures on beach erosion
• sediment cell is the basic unit of shoreline management in England and Wales

Question 10

Problems with the sediment cell concept

Answer 10

• cells are based upon the movement of coarser particles rather than movement of suspended finer materials
• easy for fine sediment to find their way around headlands and into neighbouring cells
• therefore cell boundaries in such a dynamic system cannot be fixed/static (closed system) as the sediment cell concept suggests