What is a sediment cell or Littoral cell ?A stretch of coastline which sediment issourced, transported and deposited.The cell is essentially closed to sedimentfrom other cells but some transfers maytake place.The cell is bounded by coastal features i.e.headlands or different Longshore driftdirections
SEDIMENT CELL / LITTORAL CELLThe cell is a system that is essentially closed to sediment fromother cells but receives INPUTS from within the cell and fromthe land.After being transported, the sediment is deposited in SINKS(longterm stores), which effectively remove the sediment fromtheTRANSFER processes within a cell.The sediment may well remain geographically part of the cellbut not interact with Longshore drift currents and waves socould be termed an OUTPUT.
Source INPUT Transported or Deposited TRANSFER PROCESS SINK• Eroding cliffs • Long shore • Depositional drift Features• Eroding e.g. beaches, depositional • Tidal bars, dunes features• e.g. beaches • Currents • Submarine• River/ Estuary canyons sediment• Offshore Bars
Fig. 2 shows an imaginarycoastline with INPUTS ofsediment, TRANSFERprocesses and SINKS/ Storesof sediment.The first diagram shows ahealthy cell where sedimentmoves from INPUTS toSINKS freely.The second diagram showswhat can happen if thesediment cell is disrupted byHuman activity and defences.
A broad beach is the best defence againstthe sea and the health of the beaches in thecell rely on a reliable supply of sediment.If sediment is prevented from moving downthe coastline then there could be increasederosion of beaches and cliffs elsewhere downdrift.
For example, erecting a largesea wall and putting in groynesmay stop a cliff eroding and akeep a town’s beach in placebut may starve beaches downdrift, causing erosion.
The Promontory effect seen here is a feature ofthe NE Norfolk Coastline at present.
The sediment cell for NENorfolk relies on an input of sediment from theerosion of cliffs, offshoredeposits and river inlets which are then transported in adominantly southwards direction down the North Sea coast towards the beaches of Gt.Yarmouth and Lowestoft.
A LEVEL PAPER QUESTIONSDescribe the sources, transportation and deposition ofcoastal sediments. Illustrate your answer by reference toexamples of coastal landforms that are produced by theseprocesses. – NOV 2007Describe the nature of a coastal sediment cell. How dothese cells contribute to the formation of coastallandforms. – JUNE 2007