Coast

Littoral zone

An area of shoreline where land is subject to wave action

Subdivisions of littoral zone

Coasts, backshore, foreshore, nearshore, offshore

Concordant coasts

Sometimes referred to as Pacific coasts. Alternating layers of hard and soft rock that run parallel to the coast. (e.g. Dalmatian coast)

Discordant coasts

Sometimes referred to as Atlantic coasts. Alternating layers of hard and soft rock that are perpendicular to the coast. (e.g. West Cork, Ireland)

Joints

These divide rock strata up in blocks with a regular shape.

Fissures

Smaller cracks in rocks. Often they are only a few cms long.

Fault

A mojor line of weakness within the rock. This causes large fractures.

Factors that affect the size of waves

Fetch, wind strength, depth of water.

How are waves formed

By wind blowing over the surface of the sea. As the wind blows over the sea, friction is created-producing a swell in the water. It is the energy within the wave and not the water that moves.

Why do waves break

1. Waves start out at sea.

2. As waves approach the shore, friction slows the base.

3. This causes the orbit to become more elliptical.

4. Eventually the wave breaks over.

Constructive waves

The wave has a swash that is stronger than the backwash. This builds up the coast.

Destructive waves

The wave has a backswash that is stronger than the swash. This erodes the coast.

Formation of a coastal stack

1. Hydraulic action widens crack in the cliff face over time.

2. Abrasion forms a wave cut notch between HT and LT.

3. Further abrasion widens the wave cut notch to form a cave.

4. Caves from both sides of the headland break through to form an arch.

5. Weather above/erosion below - arch collapses leaving a stack.

6. Further weathering and erosion leaves a stump.

Formation of bays and headlands

1. Waves attack the coastline.

2. Softer rock is eroded by the sea quicker forming a bay, calm areas causes deposition.

3. More resistant rock is left jutting out into the sea (headland)

Wave refraction

The bending of a wave due to its interaction with the seabed’s topography and/or the shape of its coastline.

Cliff retreat/ wave cut notch and platform

1. Wave cut notch becomes deeper, the overhanging rock above is then unstable and collapses.

2. Repeated cycles of notch-cutting and collapse cause the cliffs to recede inland.

3. Former cliff position is shown by the horizontal rock platform visible at low tide. ( i.e. a wave cut platform)

Sand dune succession

1. Embryo dune

2. Yellow dune

3. Grey dune

4. Dune slacks

5. Climax

Why vegetation is important in stabilising coastlines

Roots bind sediment together, provides a protective layer to prevent exposure, protection from wind erosion.

Deposition

When the sea loses energy, it drops sand, rock particles and pebbles it has been carrying. It can occur on coastlines that have constructive waves.

Lithology

The general physical characteristics of a rock or the rocks in a partiular area. Affects the rate of coastal recession and stability.

Attrition

Rocks that bash together to become smooth/ smaller

Solution

A chemical reaction that dissolves rock

Abrasion

Rocks hurled at the base of a cliff to break pieces apart

Hydraulic action

Water enters cracks in the cliff, air compresses, causing the crack to expand

Solution (transportation)

Minerals dissolved in water and are carried along.

Suspension

Sediment is carried along in the flow of the water

Saltation

Pebbles that bounce along the seabed

Traction

Boulders that roll along a seabed by the force of the flowing water.

Subaerial processes

A breakdown of rock when they are exposed to the atmosphere in situ. Chemical, mechanical and biological.

Mass movement

A movement of soil and rock debris that moves downslope in response to the pull of gravity.

Types of mass movement

Rockfall, rotational slumping, landslides.

Sedimentary

Weathering and erosion of rocks exposed at the surface (Sandstone)

Metamorphic

Rocks under high temps and pressure change composition (Slate)

Igneous

Formed by the cooling and solidifying of molten rock.

Depositional features

1. Bayhead beach

2. Tombolo

3. Barrier beach/bar

4. Cuspate foreland

Bayhead beach

Waes break at 90 degrees to the shoreline and moves sediment into a bay

Tombolo

A sand or shingle bar that links the coastline to an offshore island

Barrier beach/bar

A sand or shingle beach connecting two areas of land with a lagoon behind

Cuspate foreland

Triangular shapes features extending out from a shoreline.

Sediment cells

Act as a part of a system- with sources, transfer and sinks. The system aims for equilibrium between inputs and outputs. (dynamic equilibrium)

Groynes

Wood or rock barriers that slow longhsore drift, so the beach can build up. Beach is still accessible, but it means there is no deposition further down the coast.

Seawalls

Concrete walls break up the energy of waves. Has a lip to stop waves going over. Long life span and protects from flooding. Very expensive

Rip rap

Boulders that are resistant to erosion with large surface to break up waves. Long lasting and effective at absorbing energy. Sea water still moves through it.

Gabions

Pebbles in a wire basket. Very flexible with placement. Need frequent repairs.

Beach nourishment

Beaches built up with sand, so waves have to travel further before erodiong cliffs. Cheap and suitable for tourists. Storms= need replacing. Offshore dredging damages seabed.

Managed retreat

Low value areas of the coast left to flood and erode naturally. Reduces flood risk, creates wildlife habitats. Does not prevent land being lost.

Positives of soft engineering

Low cost, less impact on environment, a more natural visual appearance.

Negatives of soft engineering

Needs regular maintenance, less likely to be effective against extreme storm events, people may have to be compensated for property loss,

Positives of hard engineering

• Quick / one off solution that protects the coastline

• Reassures coastal communities

• Reduce insurance costs of homes in high risk ares

• Usually quite effective

Negatives of hard engineering

• High costs

• Requires maintenance

• Make the coast unattractive for tourists

• Have adverse affects down drift from the defences.

Isostatic Changes

Local changes in land and sea levels

Eustatic Changes

Changes which affect worldwide sea levels

Emergent coastlines

Formed as a result of a relative fall in sea level. Raised beaches (Isle of Arran, Scotland), Relict cliffs (Ayrshire, Scotland)

Submergent coastlines

Result of sea level rise. Rias (kingsbridge, devon), Fjords (Isle os Islay, Scotland)

Causes of coastal flooding

Large waves, sever weather events, low lying coasts, global sea level rise due to climate change.

Integrated Coastal Zone Management (ICZM)

National and sometimes international scale policy for a large stretch of coastline.

Shoreline Managment Plan (SMP)

Regional scale management for a specific stretch of coast. Normally for a sediment cell.

Management Unit

Local scale management for a small stretch of coast within a sediment cell (subcell).

Cost Benefit Analysis

This comapres the cost of coastal defences with the value of the land to be protected

Environmental Impact Assessment

The aims to identify the environmental positives and negatives of a development before it is implemented.

Coastal Management. Odisha, India

• North east coast

• Range of unique environments

• Potential for offshore renewable energy

• Rapid urban, industrialisation, tourism, coastal erosion, oil and gass production, rising sea levels, fishing

• Planting/replating mangrove forests, developments to facilitate eco-tourism

Hold the line

Maintain the existing coast by building defences

Advance the line

Build new defences outwards into the sea

Strategic realignment

Allow the land to flood and construct new line of defence inland

No intervention

Allow natural processes to shape the coastline.