COAST Processes & COAST Processes & ProblemsProblems

Autumn 2008Autumn 2008

The coastal zone is a narrow zone where the land and sea overlap & directly interact. “…a battle

ground between the forces of waves and the strength of the land.”

Some key termsSome key terms COASTCOAST

Onshore, offshore…Onshore, offshore… FETCHFETCH WAVEWAVE

ConstructiveConstructive DestructiveDestructive

SwashSwash BackwashBackwash

Why are coasts so Why are coasts so important?important?

Why are coasts so Why are coasts so important?important?

Interface between land and seaInterface between land and sea Hazardous area due to erosion and floodingHazardous area due to erosion and flooding Long term/short term changesLong term/short term changes Human activity affect ecosystems/habitat eg coral Human activity affect ecosystems/habitat eg coral

reefreef Half the worlds population live within 60km of the Half the worlds population live within 60km of the

coast, 2/3 of major citiescoast, 2/3 of major cities Competition for resourcesCompetition for resources Provides economic activity- tourism, farming etcProvides economic activity- tourism, farming etc Management needed to be sustainableManagement needed to be sustainable

Coasts are an open systemCoasts are an open system

Coasts are an open systemCoasts are an open system

Inputs?Inputs? Energy & Sediment – Waves, winds, Energy & Sediment – Waves, winds,

tides, currents.tides, currents. Processes?Processes?

E, T, DE, T, D Outputs?Outputs?

Deposited material onshore, landformsDeposited material onshore, landforms

Coasts are an open systemCoasts are an open system

Fluvial systems -estuaries and deltas Fluvial systems -estuaries and deltas (discharge and sediment)(discharge and sediment)

Sub-aerial systems –onshore (run-off, Sub-aerial systems –onshore (run-off, weathering and mass movement)weathering and mass movement)

Coastal systems –inshore (beaches Coastal systems –inshore (beaches and ecosystems)and ecosystems)

Marine systems –offshore (waves, Marine systems –offshore (waves, tides and sediments)tides and sediments)

Beaches occupy the Beaches occupy the littorallittoral zone zone between the highest and lowest between the highest and lowest spring tidesspring tides

Movement of sediment along the Movement of sediment along the shore creates a number of distinct shore creates a number of distinct “sediment/littoral cells.”“sediment/littoral cells.”

So: What’s a Sediment Cell?So: What’s a Sediment Cell? “…“…movement of sand and shingle in the movement of sand and shingle in the

nearshore zone by longshore drift has nearshore zone by longshore drift has been found to occur in discrete, been found to occur in discrete, functionally separate sediment cells. There functionally separate sediment cells. There are 11 such cells around England and are 11 such cells around England and Wales. They are defined as a length of Wales. They are defined as a length of coastline and its associated nearshore coastline and its associated nearshore area within which the movement of coarse area within which the movement of coarse sediment (sand and shingle) is largely self sediment (sand and shingle) is largely self contained.” contained.”

Littoral cells around England and Wales

Inform SMP’s

DeltasDeltas

Deltas are a delicate balance of Deltas are a delicate balance of aggrading (up) and subsiding aggrading (up) and subsiding (down) processes(down) processes Up: deposition of sediment, Up: deposition of sediment,

accumulation of organic materialaccumulation of organic material Down: compaction of seds, tectonic Down: compaction of seds, tectonic

subsidence (wt of seds), erosionsubsidence (wt of seds), erosion

DeltasDeltas

Why is there no Why is there no Columbia River Columbia River Delta?Delta?

Why no C.R. Delta?Why no C.R. Delta?

1.1. because it is a smaller river than because it is a smaller river than the Mississippi thus it does not the Mississippi thus it does not generate the amount of sediment generate the amount of sediment that would be needed.that would be needed.

Why no C.R. Delta?Why no C.R. Delta?

1.1. because of the many dams that have because of the many dams that have been built which control the been built which control the sediment flow along with the river, sediment flow along with the river, so no large amounts of sediments so no large amounts of sediments are being deposited where the river are being deposited where the river enters the ocean. enters the ocean.

Why no C.R. Delta?Why no C.R. Delta?

1.1. ...in the case of the Columbia ...in the case of the Columbia river, the ocean waves and river, the ocean waves and powerful currents quickly powerful currents quickly redistribute the material that redistribute the material that is being deposited so it is being deposited so it allows for no sediment to allows for no sediment to build up and form a delta build up and form a delta rather it redistributes it.rather it redistributes it.

DeltasDeltas

Deltas are a delicate balance of Deltas are a delicate balance of aggrading (up) and subsiding aggrading (up) and subsiding (down) processes(down) processes Up: deposition of sediment, Up: deposition of sediment,

accumulation of organic materialaccumulation of organic material Down: compaction of seds, tectonic Down: compaction of seds, tectonic

subsidence (wt of seds), erosionsubsidence (wt of seds), erosion Effective ‘down’: sea level riseEffective ‘down’: sea level rise

Which way is the

longshore current?

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

Land (Land (terrestrialterrestrial)) Sea (Sea (marinemarine)) Weather and climate (Weather and climate (atmosphericatmospheric)) Human activities Human activities

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

LandLand

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

LandLand shape of coastline, shape of coastline, relief of land, relief of land, presence or lack of beach, presence or lack of beach, Geology: structure of the coast & resistance of Geology: structure of the coast & resistance of

the rocks, the rocks, sub-aerial processes (weathering), sub-aerial processes (weathering), river sediments, river sediments, coastal (land) ecosystemscoastal (land) ecosystems

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

SeaSea

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

SeaSea Coastal (marine) ecosystemsCoastal (marine) ecosystems Wave energy and directionWave energy and direction Size and type of wavesSize and type of waves Local currents and longshore driftLocal currents and longshore drift Tidal changesTidal changes Water depthWater depth Offshore sedimentsOffshore sediments Longer-term changes in sea levelLonger-term changes in sea level

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

Weather and climateWeather and climate

Human activitiesHuman activities

Factors affecting Coastal Factors affecting Coastal environmentsenvironments

Weather and climateWeather and climate Wind strength and directionWind strength and direction Rainfall and temperatureRainfall and temperature StormsStorms Climate change (global warming) ?Climate change (global warming) ?

Human activitiesHuman activities Intervention into natural systems – Defence – Industry…Intervention into natural systems – Defence – Industry…

Agriculture, developments, tourism, gravel extraction, recreationAgriculture, developments, tourism, gravel extraction, recreation Use of land for developmentUse of land for development

Processes of changeProcesses of change

Draw a diagram of a coastline/cliff Draw a diagram of a coastline/cliff with all the processes you can think with all the processes you can think of that will change it.of that will change it.

Lesson 1&2 Noting Lesson 1&2 Noting Activities:Activities:

Why is the coastline an example of an Why is the coastline an example of an open system?open system?

List some inputs & outputs to the List some inputs & outputs to the systemsystem

Homework: Due in next Tuesday:Homework: Due in next Tuesday:““DESCRIBE & EXPLAIN why the coast is DESCRIBE & EXPLAIN why the coast is

such a difficult environment to such a difficult environment to attempt to manage.”attempt to manage.”