Topic 4 - Costal Weathering And Erosion (set E)✔️ Flashcards
Explain longshore drift?
Process where waves follow the direction of the prevailing wind - swash carries material up the beach in the same direction as the waves - backwash then carries material down the beach at right angles, back towards the sea - over time material zigzags along the coast
Explain what constructive waves are?
- Smaller, longer waves which deposit sediment up the beach, as a result of their strong swash and weak backwash (which doesn’t take much material back down the coast) - low frequency
Whats ithe frequency of contructive waves?
Low - around 6-8 waves per minute
What is deposition? What is it caused by?
- When material being carried by seawater is dropped on the coast - occurs when water carrying sediment slows down - sand and shingle deposited by constructive waves
Explain how spits form?
- Form at sharp bends in the coastline - longshore drift transports sand and shingle past the bend and deposits it in the sea - strong winds can curve the end of the spit forming a recurved end
Significance of the area behind a spit?
- area behind the spit is sheltered and protected from waves - lots of material acumulates here and over time becomes a mud flat or salt marsh
Explain how a bar is formed?
- A bar is formed when a spit joins two headlands together - the bar cuts of the bay between the headlands from the sea - which creates a lagoon behind the bar
Explain how a lagoon is formed?
- When a bay is cut of by a spit joining two headlands together - the bay is cut of from the sea by the bar which forms a lagoon behind it
Difference between sand beaches and shingle beaches on a map?
- Sand beaches are shown as pale yellow - shingle beaches are shown as white or yellow with speckles
Explain how agriculture can have indirect effects on the coast
- agricultural land often has low economic value - often left unprotected and left to erode
- clearing vegetation (which helps bind the soil together) to make room for crops, leaves the soil exposed and vunreable to weathering by rain and wind - can affect stability of cliffs
Explain how development can have indirect effects on the coast?
- will be higher value land - have more coastal defenses so the land is better protected from erosion
- effects transportation and deposition of materials negativley - can restrict sediment supply to other beaches making them narrower and more vunreable to erosion
What is a direct effect on the coastline?
- Are the immediate results of human activities - for example building coastal defenses which will prevent erosion
What is a indirect effect on the coastline?
- Happens as a result of the direct effects - for example building coastal defenses will prevent erosion in one place, but can increase erosion further down the coast
Explain how industry can have indirect effects on the coast?
- coastal quarries expose large areas of rock - making them more vunreable to chemical weathering and erosion
- gravel has been extracted from beaches to be used in the construction industry (eg making concrete) - less material to protect cliffs
Features of the holderness coast?
- high rates of erosion - average of 1.8m a year lost to sea
- cliffs mostly made of boulder clay - easily eroded and slumps when wet (causing cliffs to collapse)
- narrow coasts - cliffs lacks protection
How has prevailing winds affected the holderness coast?
- Faces the prevailing wind direction, which brings powerful, erosive waves from the north east (all the way from the norwegian sea)
- eroded material is moved south instead of staying in the place it came from - exposing new areas of cliff to erosion
How is the holderness coast protected by coastal defenses?
- 11km protected by hard engineering techniques
- groynes have been built at mappleton
- sea walls have been built
How have coastal defenses causes problems along the holderness coast - give 3 examples?
- groynes have caused narrow beaches to form further down the coast
- reduced material transported south - increases the risk of flooding because there is less material to slow floodwater down
- bays forming between the protected areas, protected areas are becoming headlands which are being eroded more heavily
How do rising sea levels increase the risk of coastal flooding?
- higher sea levels could cause higher tides - which would flood coastal areas more frequently - tides could also removes large amounts of material from beaches which could result in increased erosion
How do changes in storm frequency increase the risk of coastal flooding - Give 2 ways?
- Storms are becoming more frequent - storms gives the sea more erosional power so areas of hard rock will be more vunreable
- sea will have more energy to transport material - high energy waves can move material for greater distances - leaves some areas being starved of material
Give 3 examples of threats to people through coastal flooding?
- coastal industries may shut down because of damage to equipment and buildings eg fishing boats being destroyed
- risk of damage to infrastructure like roads and rail networks
- tourist industrys in coastal areas could be lost - loss of jobs
Give 3 examples of threats to the enviorment through coastal flooding?
- ecosystems will be affected by high salt content in sea water - can make soil infertile
- force of floodwater can uproot trees and plants
- conservation areas like lagoons (seperated from the sea by a bar) could be destroyed
Explain how hard engineering like a sea wall works?
Wall made of hard material like concrete - reflects waves back to sea
2 pros of sea walls?
- prevents erosion of the coast
- acts as a barrier to prevent flooding
2 cons of sea walls?
- creates a strong backwash which erodes under the wall
- sea walls are exoensive to build and maintain
Explain how hard engineering like groynes works?
Wooden or stone fences that are built at right angles to the coast - trap the material transported by longshore drift
2 pros of groynes?
- create wider beaches - which slows the waves and gives greater protection from flooding and erosion
- fairly cheap defense
Define hard engineering?
Man made structure built to control the flow of the sea and reduce flooding and erosion
Define soft engineering?
Schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion
Explain how soft engineering like beach replenshiment works?
Sand and shingle from elsewhere (eg from seabed) or from lower down the beach are added to the upper part of beaches
What is a benefit of beach replenshiment?
creates wider beaches which slows the waves and gives greater protection against flooding and erosion
What are 3 cons of beach replenishment?
- Taking the material from the seabed can kill organisms
- very expenisve
- has to be repeated
Explain how soft engineering like slope stabilisation works?
Slopes are reinforced by inserting concrete nails into the ground and convering the slope with metal netting
What is a benefit of slope stabilisation?
Prevents mass movement by increasing the strength of the slope
What is a con with slope stabilisation?
Slope stabalisation is very expensive and sometimes difficult to install
Explain how soft engineering like strategic realignment works?
Removing an existing defence and allowing the land behind it to flood
What are benefits of strategic realignment?
- overtime the land will become mashland -creates new habitats
- flooding an erosion are reduced behind the marshland
What is an issue with strategic realignment?
- people will disagree over what land is allowed to flood - flooding farmland would affect the livelihood of farmers
Why might a ‘do nothing strategy’ be usefull for coastal management?
- doesn’t cost anything to let the coast retreat naturally - can cause people to be forced to move away
- erosion and flooding can be delt with as they happen
What 2 important features of management strategies?
- need to be sustainable - means making sure erosion and flooding is controlled without causing more problems
- needs to be cheap and avoid conflicts about the spending of public money
Explain the role of intergrated coastal zone management (ICZM)?
Is an approach that aims to protect the coast while taking everyones intrests into account - makes it easier to find solutions, everyone agrees with
