Coasts Flashcards

Question

Revetments (hard)

Answer 1

A sloping concrete (£2000 per metre) or wooden (much cheaper) wall that slopes along the coast. The wooden walls have open structures which absorb the wave energy but allows sediment to build up beyond as well. They are more effective than sea walls but are environmentally ugly.

Answer 2

These are piles of large boulders placed at the foot of a cliff that force the waves to break their energy. It costs between £1,000-£4,000 a metre but are relatively easy to maintain. However, they are environmentally ugly, obtrusive and expensive to transport.

Answer 3

A wall made of interlocking material or concrete just below the water mark that protects the shore from all waves. It costs around £5000 per metre (expensive!) It is effective as it decreases the strength of hydraulic power, but if the tide is out, it is ugly, obtrusive and dangerous to swim around.

Answer 4

These are steel mesh cages filled with small rocks in order to absorb wave energy they are fairly cheap, more effective than sea walls- but environmentally ugly.

Answer 5

These are narrow walls built out into the sea to prevent longshore drift and erosion. They are £10,000 each and need to be placed every 200 metres in order for it to be effective. However, they are often spaced too far apart and ugly.

Answer 6

Maintaining the existing coast by building defences

Answer 7

Build more defects outwards into the sea

Answer 8

Allowing the land to flood and construct a new line of defence inland

Answer 9

Allowing natural processes to shape the coastline

Answer 10

``` Home to 850 people No less than 18 listed buildings Houses costing as little as £1 Happisburgh protects the Norfolk broads (Agricultural =67%, residential = 22%, public = 6%, tourism = 4%, commercial = 1%) ``` If erosion continues : 1000's of tonnes of cliff material lost (40ft lost per year) Many houses will be lost to sea (30 already) Economy and tourist industry severely damaged SMP: - Originally timber revetments in 1950's but destroyed by waves and by 2000 little defence remained - A rock bund was created in front of cliff in 2002 using 4000 tonnes of boulders - In 2006 the SMP said the area should enforce managed retreat

Answer 11

- Home to 488 people - Significant tourist industry - Beaches have blue flag status encouraging watersports - Sand dunes protect 6000 acres of the Norfolk broads -behind Sea Palling - Beaches have built up considerably due to sea defences If erosion continues ; lifeboat station will be lost 6000 acres of Norfolk broads lost - has a land value of £345 million and £500,000 SMP : -Sea wall built in 1953 - 100,000 tonnes of boulders placed in front of sea wall - 1 million cubic metres of sand brought in to replenish beach - 4 offshore reefs built parallel to coast - a second set later added to the south (reefs break waves before they reach the beach + absorb storm energy)

Answer 12

Hurst castle spit is a spit in Hampshire caused by waves approaching the beach in the direction of North East, transporting sediment. The spit is roughly 2km long and has a width of 150m.

Answer 13

A spit is a long finger of land along the coastline, jutting out into the sea, where sediment has been deposited due to longshore drift. The angle at which the swash of the waves hits the beach due to prevailing winds transports sediment along the coast until the coastline changes it direction or meets a river mouth. As more and more sediment is deposited the spit extends into the sea and eventually the tip curves round due to prevailing winds to form a hook

Answer 14

Where : Christchurch Bay, Hampshire What : Coastal erosion and cliff collapse --> buildings lost to the sea - eroding 2m per year Who : Local people and businesses, tourist industry, wildlife and the landscape Why : 1) Rocks are weak sand and clays which are easily eroded by the sea and have little strength to resist collapse 2) Arrangement of rocks (Permeable sands on top of impermeable clay) causes the water to 'pond-up', increasing the weight of the cliffs (Increase in water pressure) encouraging collapse 3) This stretch of coastline faces the direct force of prevailing south-westerly wind. With a long fetch the waves approaching barton-on-sea are powerful causing a lot of erosion 4) Small dreams flow towards the coast but are stopped by permeable sands before they reach the sea -->adding to the amount of water in the cliffs 5) Buildings on the top of the cliff increase weight upon the cliffs --> more venerable to collapse (also interfere with drainage)

Answer 15

1) A salt march begins when mud and silt begin to collect at a sheltered part of the coastline, where deposition can be deposited, but the area is too sheltered for the tide to pull it away 2) Deposited silt builds up in layers over time, to form mudflats that break through the surface of the water 3) Some plants begin to grow the first is cordgrass Pioneer plant). It is tolerant to sea water (a halophyte) and has long roots the help keep mud and sediment together. As the mudflats rise, they are no longer covered by high-tides and this allows the rain and any fresh water from rivers to wash out the salt. Lower salt concentration = more plants that grow due to more fertile soil - such as sea asters (second generation) and eventually bigger and hardier plants such as trees = VEGETATION SUCCESSION

Answer 16

Key haven salt marsh is retreating by up to 6m a year Specialties of Keyhaven ; 1) special species of plant and animal e.g cordgrass, oyster catcher, sea lavender, rigid plover, common blue butterfly and wold spider 2) SSSI (Site of special scientific interest) Threats to Keyhaven : 1) Sea levels are rising = squeezing of salt marshes because of presence of sea walls 2) Storm events can erode the spit ; In 1989 the spit was breached by a storm, exposing the salt marsh to the sea. Destructive waves eroded 50-80m of salt marsh in 3 months 3) Tourists e.g walkers cause erosion to the mudflats and possibly the spit --> rubbish, cars, anchors mooring within the wetlands Management of key haven : - In 1996 rock armour and beach nourishment were added to the spit, to increase its height and width in attempt to stop breaching (this caused waves to break early and stop erosion of shingle) - Designated area of SSSI - laws and restrictions to protect it --> central car park to contain effects + designate paths for visitors, to make sure most areas are left untouched, preventing erosion

Answer 17

Settlements such as King's Lynn may be under threat as sea levels rise and valuable agricultural land such as the Fens will be at greater risk from flooding. As sea levels rise, erosion rates are likely to increase- threatening the coastal settlements such as Overstrand and Happisburgh. This will mean that current sea defences will need strengthening, which is expensive.

Answer 18

In 1953, East Anglia suffered terribly from a storm surge that killed 300 people. People are worried that such an event may happen again so people do not come.

Answer 19

As a result of the Fens flooding, farmers may not have another source of income - could be badly affected by the flooding. The Thames barrier currently protects buildings worth £80bn. It will probably need to be replaced in the next 30-50 years. As sea levels rise, large areas of the lower Thames estuary will be at risk from flooding, affecting housing, industry and farmland. The Norfolk boards are a popular tourist destination , bringing £5m pounds to the area. Sea level rise would flood the broads, destroying the economy of the area.

Answer 20

Low lying mudflats and marshes in Essex are particularly vulnerable to sea level rise. Areas of salt marsh are being squeezed in between sea walls and rising sea. Some 22% of salt marshes could be lost by 2050- so in some places, managed retreat will break sea walls to allow deliberate flooding so that salt marshes can reform. This is politically controversial.

Coasts Flashcards

(44 cards)