The Coastal Zone

Mechanical Weathering- the breakdown of rock without changing its chemical composition.

Freeze-thaw weathering:

• When the temperature alternates above and below 0C.
• Water gets into the rocks that formed cracks (granite).
• The water expands when it freezes, which puts pressure on the rock.
• The water contracts when it thaws, releasing the pressure on the rock.
• Repeated freezing and thawing causes the rock to break up.

Chemical Weathering- the breakdown of rock by changing its chemical composition.

Carbonation weathering:

• Rainwater contains carbon dioxide which makes it a weak carbonic acid.
• This reacts with the rock that contains calcium carbonate, dissolving rocks like limestone.
• Occurs in both wet and warm weather.

Hydraulic Power:

• Waves crash against the rock and compress the air in the cracks, putting pressure on the rock.
• Repeated compression widens the crack and makes them break off.

Abrasion:

• Eroded particles in the water scrape and rub against the rock, removing small pieces.

Attrition:

• Eroded particles in the water smash against each other, breaking into smaller pieces. The edges are rounded off into smooth pebbles.

Solution:

• Weak carbonic acid in seawater dissolves rock like chalk and limestone.

Mass Movement:

• The shifting of rocks and loose material down a slope. When the force of gravity acting on a slope is greater than the force supporting it.
• Mass movements cause coasts to retreat rapidly.
• More likely to occur when the material is full of water.
• Slides shift material in a straight line / Slumps shift material with a rotation.

Wave-Cut Platforms:

• Waves cause most erosion at the foot of a cliff.
• A wave-cut notch forms, which is enlarged as erosion continues.
• The rock above the notch becomes unstable and eventually collapses.
• The collapsed material is washed away and a new wave-cut notch is formed.
• Repeated collapsing results in cliff retreating.
• A wave cut platform is the platform that is left behind as the cliff retreats.

Headlands and Bays:

• Headlands and bays are formed when there are alternating bands of resistant and less resistant rock along a coast.
• The less resistant rock (clay) is eroded quickly which forms a bay, which have a gentle slope.
• The resistant rock (chalk) is eroded slowly and is left jutting out, forming a headland, which have steep sides.

Caves, Arches, Stacks:

• Headlands usually consist of cracks.
• Waves crash into the headlands and enlarge the cracks, through hydraulic power / abrasion.
• Repeated erosion and enlargement of cracks cause caves to form.
• Erosion continues to deepen the cave until it breaks through, forming an arch.
• Erosion continues still until the arch collapses.
• This forms a stack - an isolated rock seperate from the headland.

Longshore drift- material transported along coasts by a process called longshore drift.

Process:

• Waves follow the direction of the prevailing wind, which hit the coast at an oblique angle.
• The swash carries material up the beach in the same direction as the waves.
• The backwash carries material down the beach at right angles back towards the sea.

Traction- large particles like boulders pushed along sea bed by force of the water.

Saltation- pebble-sized particles bounced along the sea bed by the force of water.

Suspension- small particles like silt and clay are carried along the water.

Solution- soluble materials dissolve water and are carried along.

Deposition- when material being carried by sea water is dropped on the coast.

Coasts are built up when the amount of deposition is greater than the amount of erosion.

Amount of deposition depends upon:

• Amount of erosion elsewhere on the coast.
• Amount of transportation in the area.

Low energy waves carry material to the coast, but not strong enough to take it away. This results in lots of deposition and little erosion.

Constructive Waves:

• These waves have a low frequency (6-8 waves per minute).
• They're low and long.
• The swash is powerful and it carries material up the coast.
• The backwash is weaker and doesn't take a lot of material back down the coast.

Beaches (deposition):

• Beaches are found on coasts between the high water mark and the low water mark.
• Formed by constructive waves which deposit sand and shingle.
• Sand beaches are flat and wide / Shingle beaches are steep and narrow.

Spits (Longshore Drift):

• Spits form at sharp bends in the coastline (river mouth).
• Longshore drift transports sand and shingle past the bend and deposits it in the sea.
• Strong winds/waves curve at the end of the spit, forming a recurved end.
• The sheltered area behind the spit is protected from waves, which means plants grow there.
• Overtime, the sheltered area can become a mud flat or a salt marsh.

Bars (Longshore Drift):

• A bar is formed when a spit joins two headlands together
• The bar cuts off the bay between the headlands from the sea, forming a lagoon behind the bar.

Erosion Landforms:

• Caves and arches can't be seen on the map.
• Stacks look like small blobs in the sea.
• Cliffs are shown as little black lines on the map.
• Wave-cut platforms are shown as bumpy edges along the coast.

Deposition Landforms:

• Sand beaches are shown on maps as pale yellow.
• Shingle beaches are shown as white or yellow with speckles.
• Spits are shown by a beach that carries on out to sea,but is still attached to the land at one end
• There may also be a sharp bend in the coast that caused it to form.

• Melting Ice- global warming causes water that's stored as ice to return to the oceans.
• Heating Oceans- causes oceans to get warmer and expand, thermal expansion.

Economic:

• Tourism Loss - flooding can cause tourist attractions to close and put people off visiting.
• Damage repair - repairing flood damage can be extremely expensive.
• Loss of agricultural land- high seawater salt content reduces soil fertility.

Social:

• Coastal flooding has resulted in thousands of deaths in the past.
• Loss of housing and jobs.
• Water supplies polluted with salt or sewage.

Environmental:

• Increased salt levels can affect ecosystems.
• Vegetation killed by water, with the force of floodwater uprooting trees and plants.

• Population: 300,000 // No. of Islands: 1190 (199 inhabited).
• Average Island height: 1.5m above sea level (80% under 1m).

Economic Impacts:

• Loss of tourism as the largest industry in Maldives can reduce the country's income
• Disrupted fishing industry as Maldives largest export, reducing country's income.

Social Impacts:

• Houses damaged/destroyed making entire communities homeless.
• Less drinking water available due to water supplies being polluted by salty seawater.

Environmental Impacts:

• Loss of beaches destroys habitats / loss of soil means less plants can grow.

Political: The government has had to ask the Japanese government for $60m to build the 3m high sea wall protecting the capital city Male.

• The Holderness coastline is 61km long, stretching from Flamborough Head to Spurn Head.
• Erosion causes the cliffs to collapse along the coastline.
• The average rate of erosion at Holderness is about 1.8m per year.

Reasons for rapid erosion:

• The cliffs are made of boulder clay which is easily eroded.
• Narrow beaches give less protection to slow waves down.
• Groynes are used at Mappleton, but make the beach narrower,increasing erosion elsewhere.
• Holderness face prevaling wind direction from the north east,making the waves highly erosive

Social Impacts:

• Homes near cliffs (Skipsea) are at risk of collapsing into the sea, affecting property prices
• Roads are at risk of falling into the sea (Southfield Lane).
• Businesses are at risk of erosion so people will lose their jobs.
• The gas terminal at Easington is at risk. It accounts for 25% of Britain's gas supply.
• 80,000m squared of farmland is lost each year, having a huge effect on farmers.
• Some Sites of Special Interest (Easingtoon Lagoons) are threatened.

Hard Engineering: man-made structures built to control the flow of the sea and reduce flooding and erosion.

Sea Walls- walls made out of a hard material such as concrete to reflect waves back to sea.

Benefits: prevent erosion of the coast. / Act as barrier to prevent flooding.

Problems: create a strong backwash, which erodes under the wall. / Expensive to build.

Rock Armour- where boulders are piled up along the coast.

Benefit: boulders absorb wave energy, reducing erosion / Cheaper defence.

Problems: strong waves can move the boulders, so they may need to be replaced regularly.

Groynes- wooden or stone fences that are built at right angles to the coast.

Benefits: create wider beaches which slow waves. / Cheaper defence.

Problems: affect beaches further down the coast making them narrower.   

Soft Engineering- schemes set up using knowledge of the sea and its processes to reduce erosion

Beach nourishment- when sand and shingle is added to the beaches.

• Benefit: creates wider beaches that slow the waves, giving it protection from flooding/erosion.
• Problem: taking material from seabed can kill organisms like sponges. It is very expensive.

Dune Regeneration- creating/restoring sand dunes by nourishment or planting vegetation.

• Benefit: sand dunes provide a barrier between land and sea. Stabilisation is cheap.
• Problem: protection is limited to a small area. Nourishment is very expensive.

Marsh creation- involves planting vegetation in mudflats along coasts.

• Benefit: vegetation stabilises the mudflats to reduce the wave speed. Creates new habitats.
• Problem: isn't useful where erosion rates are high. Expensive defence.

Managed retreat- removing an existing defence and allowing land behind to flood.

Strategies:

• Bridlington is protected by a 4.7km long sea wall as well as wooden groynes.
• Two rock groynes built in Mappleton in 1991. They cost £2m to protect the village and roads.
• Hornsea is protected by a sea wall, wooden groynes and rock armour.
• Spurn Head is protected by groynes and rock armour, which also protects Humber Estuary.
• Withernsea is protected by groynes and a sea wall. Rock armour was added in 1992.

Problems Elsewhere:

• Groynes protect local areas but cause narrow beaches to form further down the coast.
• Reducing the eroded material increases the risk of flooding in Humber Estuary.
• The rate of coastal retreat along Lincolnshire Coast is increased.
• Spurn Head is at risk of being eroded away because less material is being added to it.
• Bays are forming between protected areas, which are becoming headlands which are eroded more heavily.
• Maintaining the defences elsewhere is becoming more expensive.

• Studland Bay is a bay in Dorset. It is also a popular tourist destination.
• There are sand beaches around the bay,with sand dunes and a SSSI heathland behind them
• It is sheltered from erosive waves but the southern end is being eroded.

Wildlife Habitat:

• Reptiles such as grass snakes have thick, scaly skin to reduce water loss from their bodies.
• Birds like grebes are adapted to make them streamlined when they dive underwater for food.
• Marram grass has folded leaves to reduce water loss. It has long roots to stabilise in sand.
• Lyme grass has waxy leaves to reduce water loss by transpiration.

Management of Land Use:

• Boardwalks are used to guide people over the dunes so the sand is protected and not eroded
• Some sand dunes have been fenced off and marram grass planted to stabilise the sand.
• Information Signs have been placed on how visitors can use the sand dunes safely.
• Seahorses are protected by law, so boats cannot destroy the seagrass.
• The National Trust educates visitors on the dangers of causing fires and provided fire beaters to extinguish flames.