This document discusses sediment cells and sources along coastlines. It defines sediment cells as discrete areas where sediment movement is largely self-contained. Sediment can come from erosion of cliffs, sea beds, and rivers being transported by waves, currents, tides and wind. Sediment is either stored in depositional landforms like beaches or transported through the cell. The UK has 11 major sediment cells that operate in a state of dynamic equilibrium. Coastal processes like hydraulic action, abrasion, attrition, and corrosion cause different rates and types of erosion along coastlines. Mass movement processes also influence erosion, including soil creep, solifluction, and mudflows.

1. Sediment Cells and SourcesAS Geography

2. Learning ObjectivesDemonstrate an understanding of wave refractionDevelop an awareness of littoral cells and different types of sedimentDemonstrate a knowledge of coastal processes including erosionEvaluate the concepts behind mass movement

3. Wave RefractionAs waves leave deep water they become affected by frictional drag as they come into contact with the seabed

4. Sediment SourcesErosion of the cliffs can provide direct sediment inputcurrents bring in material from the sea bedRivers bring sediment downstreamThere are several methods by which sediment can reach the sea

5. What happens to sedimentSediment is either stored as a depositional landform As a nearshore feature such a bank or offshore bar. Alternatively it is transported as a throughput and become outputs from the system being deposited either in deeper water or away from the coastal area in question.

6. Types of SedimentClastic and Biogenic sedimentClastic sediments are from rock weathering and erosionBiogenicsediments are the shells and skeletons of marine organisms

7. Sediment Transport and DepositionWhat do you think is the main agent of moving sediment and depositation?Waves, currents, tides and wind move sediment from source areas and deposit it in the form of coastal land formsThese exist in a state of “Dynamic Equilibrium”

8. Sediment Cells/ Littoral CellsThese depositional landforms (such as beaches, sand dunes, salt marshes and mudflats) act as a dynamic sediment store and sediments are transported onshore, offshore, and alongshore to create them. These stores in turn provide sediment for stores further down the coast.The next slide explains this

10. Sediment Cells of the UK

11. DefinitionsThe movement of sand and shingle in the nearshore zone by longshore drift (littoral drift) has been found to occur in discrete, functionally separate sediment cells.There are 11around England and Wales. Smaller ones are within these. The main cells are defined as a length of coastline and its associated nearshore area within which the movement of coarse sediment (sand and shingle) is largely self contained. Interruptions to movement of sand and shingle within one cell should not affect beaches in an adjacent sediment Cell

12. TransportAs the particles are moved they become rounded by Attrition.Larger sediment is deposited during high energy and form beaches whilst some are also carried in suspension in areas of reduced energyAdjustments to these dynamic environments happen continuously to maintain the flux

13. Coastal ProcessesNow for the fun bitCoastlines differ due to differing erosionCoastal Erosion is the wearing away of the land by the sea.Different types of rocks wear away at different speeds and in different ways.

14. Types of erosionHydraulic Action. This is the force of water hitting the cliff and squeezing air into the cracks in the rockAbrasion. This is the force of the bits of rock carried in the water blasting into the cliff.Attrition. This is the process of rocks hitting each other and breaking into smaller rocksCorrosion. This is a chemical reaction between the sea water and the minerals in the rocks

15. The secret art of Coastal kung fu!Hydraulic Action: make punching movements with hand- demonstrates force of water hitting cliff. Abrasion: make a throwing gesture with hands like you are throwing dealing cards very rapidlyAttrition: make 2 fists, and then bring them towards each other, hitting each other, then open hand to resemble a stone breaking.Corrosion: have arms out stretched in front of you, waving fingers, and moving arms downwards. Sound effect of something dissolving is needed. Solution: Put arms out in front of you waving fingers and moving down.

16. Please Don’t be embarrassedOh OK be embarrassed thenHere we go:

17. Mass MovementExposed weathered rocks are often susceptible to mass movement

18. Soil CreepSlow less than 1cm a yearCaused by raindrop impactsWet periods add moisture to soil which swells and expands then falls down slopeFreeze thaw

19. SolifluctionOccurs mainly in colder areas, where freeze and then thaw creates movement due to lack of percolation

20. Earth flows and Mudflows, slides slumps and RockfallsFaster movements Occur on steep slopesFound often on unconsolidated slopesCan be large or small

21. Other Mass Movement ReasonsStudents are to write short paragraphs on the following separate into physical and human causesRunoffMarine ErosionWaves and BeachesGeologyHuman ActivitySea walls and Coastal DefencesLand reclamationDevelopment

22. Learning ObjectivesDemonstrate an understanding of wave refraction