Coasts Flashcards
(23 cards)
Holderness
Located = East Yorkshire
- Soft boulder clay cliffs prone to rapid erosion and slumping
- Strong destructive waves from the North Sea
- LSD Moves material southward, causing sediment starvation in some areas.
Erosion rate: Average 1.8m/year fastest rate in Europe
Management Strategies:
Mappleton (1991):
£2 million defences to protect 50 properties.
2 rock groynes + rock revetments to reduce wave energy and retain beach material
Has been effective in protecting community
Defences protect key areas but cause increased erosion further down the coast (e.g. terminal groyne syndrome).
Easington Gas Terminal: Supplies 25% of UK gas—heavily protected with rock armour due to national importance.
Spurn Head: Now mostly managed retreat due to high defence costs
Flamborough Head: Chalk cliffs naturally resistant—less intervention needed.
Sidmouth = South coast of Devon
Cliffs made of weak red sandstone and mudstone
Destructive waves from the English Channel
Erosion rate = 0.5m per year
Cliff retreat threatening homes at Pennington Point + East Beach
Risk to the SW Coast Path, local tourism, and residential areas = Estimated £72 million worth of property and infrastructure at risk over 100 years.
By 2100, up to 100m of cliff loss is predicted without intervention.
Coastal Management Strategies:
1990s Scheme – £1.5 million:
Rock armour and offshore breakwaters to reduce wave energy.
Beach replenishment to widen the beach and absorb wave energy.
New Strategy (2020 plan) – “Sidmouth and East Beach Management Scheme”:
Estimated cost: £20 million+ = which has caused delays due to public disagreement
Needed due to coastal recession
Aims = Protect 120 properties and 1,000m of road for the next 100 years.
Includes:
1 additional offshore breakwater
Beach recycling and recharge
Cliff drainage and stabilisation
Splash wall upgrade on the seafront
Part of the Shoreline Management Plan: mix of Hold the Line and Managed Retreat.
Miford On Sea
Sea level rise + greater frequency/magnitude of storms due to Climate Change
- beach = extremely volatile (rapidly changing)
- very little sediment is transported here due to the groynes to the west
- beach is not visible at low tide and vulnerable to storm surges and storm tides
- destructive waves, caused by storms of greater magnitude, remove sediment from the narrow shingle beach
- The sea wall is deflecting the waves back on to the beach which is removing more shingle
- But the wall is in danger of being undermined as shingle is eroded from its base (scouring)
Flooding is more likely to occur at Hurst Castle Spit because LSD is severely impacted by the groynes at Milford
Bangladesh
A 40 cm sea level rise would permanently submerge 11% of Bangladesh
60% of country is less than 3m above sea level
10% of the land is 1m or less above sea level
The coastline is over 600km long
Tropical cyclones and storms are common
Flooding threat can be increased by:
- downwarping = occur due to the accretion (build up) of sediment brought down by rivers that create the deltas such as in Bangladesh
- a lack of resources = Bangladesh are relatively poor and cannot afford sea defences that other richer countries can afford.
In 2007 Bangladesh was hit by Cyclone Sidr
The accompanying storm surge reached 6m high in some areas
Over 3,400 deaths
Over 55,000 injuries
Total economic losses were estimated to be US$2.31 billion
Roads, bridges and other infrastructure suffered significant damage
Example of a CBA + criticisms of DEFRA
Skipsea on the Holderness coast
Erosion rates since 1989 have been 1.4m per year on average
People in Skipsea feel that nothing has been done to protect their village with a population of 700 whilst money has been spent on coastal defences in neighbouring towns and villages
The decisions were made as a result of cost-benefit analysis
Where benefits outweigh costs, such as the sea wall at Bridlington protecting population of over 36,000 and buildings from coastal flooding, then the project is likely to go ahead
Where the costs outweigh the benefits, such as protecting the 24 houses at Skipsea from coastal erosion and flooding, a scheme is unlikely to be put in place
How many people could be displaced by sea level rise by 2100?
A study in 2011 suggested that 187 million people could be displaced by sea level rise by 2100
More recent studies suggest that has increased to 630 million people
Sediment cells
A sediment cell (or littoral cell) is a linked system of sources, transfers and sinks of sediment along a section of coastline.
The boundaries are formed by major headlands or large estuaries.
EXAMPLE = Holderness coast - transfer zone
A sediment cell operates as a closed system, with virtually no inputs or outputs of sediment from the cell.
This system contains inputs, transfers and outputs.
Inputs
Sources are places where sediment is generated, such as cliffs or eroding sand dunes.
Transfers
Places where sediment is moving alongshore through longshore drift and offshore currents. (Drift-aligned) beaches and parts of dunes and salt marshes perform this function.
Sediment cells are dynamic because the sediment is constantly generated in the source region, transported through the transfer region and deposited in the sink region.
Dynamic equilibrium is reached when inputs of sediment from the source region are balanced by the amount being deposited in sinks. It’s dynamic because although it’s in balance, there’s a constant movement of sediment through the system.
With a dynamic equilibrium, the size of the landforms in the transfer zone will remain the same. (But not the ones in the source and sink regions)
A source region may be an eroding coastline. A sink region may be an outbuilding coastline.
Feedback
Negative feedback: when the change produced creates effects that operate to reduce or work against the original change.
Positive feedback: when the changed produces an effect that operates to increase the original change.
How rock type affects beaches in the UK
Land’s End:
The resistant granite bedrock at Land’s End leads to a relatively stable coastline.
Dorset’s Chalk Cliffs:
The softer chalk cliffs in Dorset erode more readily, leading to a faster rate of coastal recession.
Swanage Bay:
The resistant Jurassic Portland Limestone forms the headland at Peveril Point, while the less resistant chalk forms the Foreland headland, influencing the indented shape of the bay.
Devensian glacial
Last glacial period in Britain
ICZM in Semarang
In Semarang, Indonesia ICZM has been implemented to reduce the risk of:
- Coastal flooding
- Subsidence
- Increased salinity
Structural:
- Embankments
- Pumping stations
- Drainage systems
- Land reclamation
Non-structural:
- Education
- Coastal planning
Ecosystem:
- Conservation of mangrove ecosystems
- Replanting mangrove ecosystems
Maldives
Lowest lying country in the world - 400k population
Maldives - 50 cm sea level rise would permanently flood 77% of land
Average height of 2m with the highest point being 2.4m
Threats have developed due to the removal of mangrove swamps
What are the Maldives doing to solve these issues:
- Large concrete sea walls, like the one around Malé (the capital city)
- The creation of Hulhumalé (reclaimed artificial island) offers a safer location for residents which is 4 m above sea level and cost $32 million to construct.
- Breakwaters = protect coastal areas from wave action
- Mangrove swamp restoration = vital natural barriers against flooding as they trap sediment and so raise the level of the beach front
Netherlands
Netherlands
27% of the country is below sea level and protected by sea defences
What are the Netherlands doing to stop this:
Building storm surge barriers across river mouths - Eastern Scheldt Barrier
part of the 2.5 billion euro project begun after the 1953 storm surge
Example of hard engineering not working
Medmerry beach near Selsey = hard defences of groynes and beach reprofiling proved to be unsustainable
Hard engineering was abandoned for a more
sustainable approach of strategic realignment.
- this works with the natural systems and crucially can cope with rising sea levels in what is a very low lying area
As result Medmerry shows that hard engineering is not always required to guarantee a future for coastal flooding threatened by coastal flooding.
Winners = environmentalists
Losers = landowners
Deposition examples
Spit = Holderness coast
Bayhead beach = Lulworth cove
Sand dunes = anywhere with marram grass/vegetation to stabilise
Weathering examples
Talus scree slope = St Oswald’s bay
Rotational scar slope
A terraced cliff profile = St Oswald’s bay
Submergent landforms
Rias = River Fowey estuary in Cornwall
Fjords in Norway
Dalmation coast
Sedimentary rocks
Shales
Sandstone
Limestone
Metamorphic rocks
Slate
Marble
Igneous rocks
Granite
Basalt
How is the UK still experiencing isostatic recovery?
Land in the North in Scotland is still rebounding and rising by 1.5mm a year
Falling in Cornwall by 1.1mm a year
Vegetation
50% salt marshes and 35% mangroves lost since 1950
100m of mangroves = reduce wave height by 13-66%
In the UK salt marshes reduce wave height by up to 80%
UK
Located = between warm tropical air and cold polar air
It experiences periods of both high pressure (anticyclones) and low pressure (depressions)
During anticyclones there are gentle winds and low waves, so rates of recession are low
During depressions the winds are much stronger, leading to high waves and greater rates of recession
A study in 2011 suggested that how many people could be displaced by sea level rise by 2100?
More recent studies suggest that has increased to how many more million people?
187 million
630 million
