Coasts

Question 1

The coastal zone

Answer 1

1 billion people live on coasts at risk from flooding.
Many live in the littoral zone, which is a dynamic area of high risk.
Risks include coastal flooding and coastal flooding.
The littoral zone is divided into:
Coast- land adjacent to the sea
Backshore- above high hide level
Foreshore- where wave processes occur. Between the high and low tide marks
Nearshore- shallow water areas close to land
Offshore- the open sea.

Question 2

Classifying coastal landscapes

Answer 2

Rocky- coastlines with cliffs
Coastal plains- land slopes gently towards the sea across an area of deposited sediment.
Primary coasts- dominated by land-based processes.
Secondary coasts- dominated by marine erosion or deposition processes.
Emergent coasts- where the coast is rising relative to sea level
Submergent coasts- coats are being flooded by the sea.
Low energy - sheltered coasts with limited fetch and low wind speeds (small waves.)
High energy- exposed coasts, facing the prevailing winds with long fetches (powerful waves.)

Question 3

Rocky coasts

Answer 3

2 main types of cliff profiles:
Marine erosion dominated: wave action dominates and cliffs tend to be steep, unvegetated with little rock debris.
Subarial process dominated: shallower, curved slope and lower relief: surface runoff erosion and mass movement are responsible.
Subarial processes- include weathering processes, mass movement processes and surface runoff erosion.

Question 4

Coastal plains

Answer 4

Low lying, low relief areas close to the coast.
Many contain estuary wetlands and marshes.
They form when:
Sea levels fell, exposing the sea bed of what was once a shallow continental shelf sea.
Sediment brought by rivers is deposited causing coastal accretion, so the coastline gradually moves seaward.
Sediment is moved from offshore sources towards the coast by ocean currents.
They are a low energy environment, lacking from large and powerful waves.

Question 5

Geological structure

Answer 5

3 elements to this:
Strata- different layers of rock
Deformation- tilting and folding by tectonic activity
Faulting- major fractures that have moved rocks from their original positions.
|t produces 2 types of coast:
Concordant- Pacific coasts where rock strata runs parallel to the coastline.
Discordant- Atlantic coasts, where different rock strata intersects the coast at an angle.

Question 6

Discordant coasts

Answer 6

Dominated by headlands and bays.
e.g.West Cork coast, Ireland.
Weak rocks are eroded to form bays
More resistant rocks form headlands.
They change over time because headlands are eroded more than bays. This happens because:
In deeper waters wave crests are parallel
As water shallows, waves slow down and wave height increases
In bays, wave crests curve to fill the bay, so height decreases.
Wave crests defract, spreading out in bays and concentrating on headlands.

Question 7

Concordant coasts

Answer 7

More complex.
Lulworth Cove:
Marine erosion breaks through the resistant beds, and then rapidly erode a wave cave behind it.
Resistant strata then prevents further erosion.
Dalmation coast in the Addriatic sea:
Geology is limestone which has been folded by tectonic activity. This has been drowned by sea level rise to create a concordant coastline of long, narrow islands arranged in lines offshore.
Haff coastlines are found at the edge of the Southern Balitic Sea. Long sediment ridges topped by sand dunes run parallel to the shore, creating lagoons between the ridges and the shoreline.

Question 8

Cliff profiles

Answer 8

They are influenced by geology:
How resistant the rock is to erosion.
The dip of strata.
Faults (rocks are heavily fractured and broken, and these weaknesses can be exploited by marine erosion)
Joints (divide up rock strata into blocks)
Fissures (much smaller cracks in the rock, but they represent weaknesses that erosion can exploit.)
Folded rocks ( heavily fissured and jointed, meaning they are more easily eroded.)
Location of micro-features found within cliffs are often controlled by the location of faults.
Also influenced by the permeability of strata, which can weaken rock layers by removing the cement that binds the rock together. W

Question 9

Holderness coasts, Yorkshire

Answer 9

Cliffs formed of unconsolidated sediment is eroded faster.

Boulder clay on the Holderness coast erodes at 2-10 m per year.

Question 10

Erosion and weathering resistance are influenced by:

Answer 10

How reactive the minerals in the rock are when exposed to chemical weathering.
Whether rocks are clastic or crystalline.
The degree to which rocks have cracks, fractures and fissures, which are weaknesses exploited by erosion and weathering.

Question 11

Coastal vegetation

Answer 11

It stabilises sediment:
Roots bind sediment together making them harder to erode.
When submerged, they provide a protective layer meaning that the sediment surface isn’t directly exposed to moving water and erosion.
Plants protect sediment from erosion by wind, by reducing wind speeds at the surface.

Question 12

Plant succession

Answer 12

Pioneer species will begin to grow in the bare sand.
This is the first stage of plant succession.
Each step in plant succession is called a seral stage.
The end result of plant succession is called a climatic climax community.
Coastal climax communities include psammosere and halosere.
Embryo dune pioneer plants:
Stabilise the mobile sand by their root systems
Reduce wind speeds at the surface, allowing more sand to be deposited
Add to dead organic matter to the sand.
Embryo dunes alter the environmental conditions from harsh, salty, mobile sand to an environment that other plants can tolerate.

Question 13

Waves

Answer 13

Waves are caused by the friction between wind and water transferring energy from the wind into the water.
The force of wind blowing on the surface of water generated ripples which grow into waves.
Wave size depends on:
The strength of the wind.
The duration the wind bows for.
The fetch.
Water depth.
Waves and water depth:
At a water depth with is approximately half the wavelength, the wave touches the seabed.
This created friction, which slows down the wave.
As they approach the shore, wavelength decreases and height increases, so waves bunch together.
The wave crest moves faster than the trough.
Eventually the crest outruns the trough and the wave topples forward.

Question 14

Constructive waves

Answer 14

Have a low wave height of less than 1 m and a wavelength of up to 100 m
Have a strong swash but a weak backwash
Swash pushes sediment up the beach, depositing it as a ridge of sediment (berm)
Have a backwash that drains into the beach sediment ,

Question 15

Destructive waves

Answer 15

Have a wave height of over 1 m and a wavelength of around 20m.
Have a strong swash that erodes beach material and carries it offshore, creating an offshore ridge.

Question 16

Beach morphology

Answer 16

Beaches experience both constructive and destructive waves, which can mean significant changes to the beach morphology:
As a storm passes, destructive waves change to constructive waves.
Between summer and winter
When there are changes to climate.

Question 17

Beach landforms

Answer 17

Storm beaches result from high level deposition of vert coarse sediment.
Berm ridges result from summer swell wave deposition
Low channels and runnels between berms
Offshore ridges / bars are formed by destructive wave erosion and subsequent deposition.

Question 18

Marine erosion

Answer 18

Most erosion occurs during a small number of large storms.
Hydraulic action- air trapped in cracks/ fissures is compressed by the force of waves. Pressure forces cracks open which dislodges blocks of rocks from the cliff face.
Abrasion- sediment is picked up by breaking waves and is thrown against the cliff face.
Attrition- numerous collisions between particles slowly chip fragments off the sediment, making it smaller and more rounded.
Corrosion- carbonate rocks are vulnerable to solution by rainwater, spray from the sea and seawater.

Question 19

Erosional coastal landforms

Answer 19

Produces a suite of distinctive coastal landforms.
Cave-arc-stack-stump sequence.
A wave cut notch is created, which is eroded by hydraulic action and abrasion.
The notch becomes deeper, and the overhanging rocks becomes unstable and eventually collapses.
Repeated cycles causes cliffs to recede inland.
The former position of the cliff is shown by a horizontal rock platform (wave-cut platform.)

Question 20

Sediment transportation

Answer 20

Traction- sediment rolls along, pushed by waves.
Saltation- sediment bounces along.
Suspension- sediment is carried in the water.
Solution- dissolved material is carried in the water.
Waves breaking at 90 degrees to the coast move sediment up and down the beach.
The process of sediment moving along the beach is called longshore drift. When wave crests break at an angle, the swash from the breaking wave and the subsequent backwash follow different angles up and down the beach, in a zig-zag pattern.

Question 21

Depositonal landforms

Answer 21

Longshore drift is a key source of sediment for these.
Sediment is deposited when the force transporting sediment drops.
This can occur in 2 ways:
Gravity settling- energy of transporting water becomes too low to move sediment.
Flocculation- clay particles clump together through electrical or chemical attraction to become large enough to sink.
Vegetation plays a key role in stabilising depositional landforms.

Question 22

Examples of depositional landforms

Answer 22

Spit- sand or shingle ridge that extends beyond a turn in the coastline.
Hooked spit- a spit whose end is curved landward, into a bay or inlet.
Tombolo- a sand or shingle ridge that links a coastlines to an offshore island.
Barrier beach/ bar- a sand or shingle beach connecting two areas of land.
Cuspate foreland- a triangular feature extending out from a shoreline.

Question 23

The sediment cell model

Answer 23

Sources - places where sediment is generated.
Transfer zones- places where sediment is moving alongshore.
Sinks- locations where the dominant process is deposition.
They have inputs, outputs and transfers of sediment.
Under natural conditions, the system operates in a state of dynamic equilibrium.

Question 24

Weathering

Answer 24

Mechanical weathering- breaks down the rock by the exertion of a physical force.
Chemical weathering- involves a chemical reaction and the generation of new chemical compounds.
Biological weathering- often speeds up mechanical or chemical weathering through the action of plants and animals.
They contribute to rates of coastal recession.
Weathering weakens rocks but making them more vulnerable to erosion or mass movement processes.
Rates of weathering are very slow.
Even in a hot, wet climate, basalt, an igneous rock, weathers at a rate of 1-2mm every 1000 years.

Question 25

Mass movement

Answer 25

Downslope movement of rock and soil.
It can be the dominant cause of cliff collapse.
Fall- rapid form of mass movement. Blocks of rock can be dislodged by erosion or weathering. Also influenced by undercutting of cliffs.
Topple- steep seaward dip. Undercutting can lead to instability, with blocks of material toppling seaward.
Rotational slide/ slumping- along a curved failure surface. Huge masses of material rotate downslope. Water influences this. They create a back-scar and terraces cliff profile.
Flow- common in weak rocks. These materials can become saturated and lose their cohesion and flow downslope.

Question 26

Sea level change

Answer 26

A rise or fall in water level causes a eustatic change.
Isostatic change is a local rise or fall in land level.
Post-glacial adjustment:
Scotland is still rebounding upward.
England and Wales are subsiding at up to 1 mm per year.
UK is pivoting with the south sinking and the north rising.
Sea level rise caused by global warming compounds the effect in the south and reduces in the north.

Question 27

Emergent coasts

Answer 27

Global sea level fell by 120 m as ice sheets grew during the last ice age. They then rose again when ice sheets melted
In North America and Northern Europe, the post-glacial Isostatic adjustment was up to 300 m.
Landforms:
Raised beaches
Fossil stump
Fossil cliff.

Question 28

Submergent coast

Answer 28

Coats being drowned when sea levels rose.
Submergent coasts are found in southern England and the east coast of America.
Ria- drowned river valleys in unglaciated areas, caused by sea level rise flooding up the river valley, making it much wider than expected.
Fjords:
U- shapes glacier valley
Often deeper than the adjacent sea.
Submerged lip.
Barrier island (East coasts of America:)
May have formed as lines of coastal sand dunes attatched to the shore.
Later sea levels have flooded the land behind the dunes, forming a lagoon but the dunes themselves weren’t eroded so became islands.

Question 29

Contemporary sea level change

Answer 29

Rising as about 2 mm per year.
Future predictions published by IPCC in 2013 range from 28cm to 98cm.
Difficult to predict because:
Thermal expansion of the oceans depends on how high global temperatures climb.
Mountain glaciers will increase ocean water volume.
Melting of major ice sheets will increase global sea level rise.
There is a lot of uncertainty over the contribution of each of these factors.

Question 30

Rapid coastal retreat

Answer 30

Have the following features in common:
Long wave fetch
Soft geology
Cliffs with structural weaknesses
Cliffs which as vulnerable to mass movement
Strong longshore drift.
Human actions can make the situation worse and usually involve interfering with the sediment cell model.
Dredging removes a sediment source which can have a knock on effect further along a coast by increasing erosion.

Question 31

Variations in erosion rate

Answer 31

Rates of erosion aren’t constant and are influenced by different factors.
Holderness coast (East Yorkshire) the average annual erosion is about 1.25 m per year (but this can vary from 0 m to 6 m)
This is because:
Coastal defences in some places have stopped erosion
These defences have starved sediment down the coast of sediment.
Erosion increases from North to South.
Varies over time:
During the winter 2-6 m of erosion is common when storms and spring tides increase erosion rates.
Summer erosion is much lower.
Ords are deep beach hollows parallel to the cliff that concentrate erosion in particular location, by allowing waves to directly attack the cliff with little energy dissipation.

Question 32

Coastal flooding risk

Answer 32

Low lying coastal land is densely populated for many reasons:
Coastlines are popular with tourists
Deltas and estuaries are ideal locations for trade
Deltas and coastal plains are especially fertile.
A sea level rise of 50 cm by 2100 would result in 77% of the Maldives disappearing.

Question 33

Storm surges

Answer 33

They are a short term rise in sea level, caused by air pressure change, either a depression or a tropical cyclone.
Strong winds push waves onshore increasing the height of the sea.
Coastal topography can narrow a coastline into an increasingly narrow space between coastlines, and as the sea shallows, the effect is severe coastal flooding.
Forecasting, evacuation, warning and improves coastal flood defences limit the scale of the damage.

Question 34

Coastal risks from global warming

Answer 34

Sea level will rise, by around 55 cm by 2100.
The area of the world’s major deltlas at risk from flooding will increase by 50%.
More large storms.
Storm surges are likely to become more common.
Some evidence of increased wind speeds and large waves.
Erosion will generally increase.

Question 35

Costs of coastal erosion

Answer 35

Loss of property, homes, businesses and farmland.
Costs of relocation and loss of livelihoods / jobs and the impact of heath.
Loss of coastal ecosystems and habitats.

Question 36

Consequences of coastal recession on coastal communities

Answer 36

Losses tend to be very localised and costs are specific to those locations.
Economic losses are very small because:
Erosion happens slowly
At risk property loses its value long before it is destroyed by erosion
Areas of high density population tend to be protected.
For coastal people, erosion means:
Falling property values, and an inability to sell their property.
Inability to ensure against the loss.
Loss of their major assets and facing the costs of getting a new home
An increasingly attractive environment.

Question 37

Consequences of coastal flooding on communities

Answer 37

Flooding tends to be on a larger areal extent and involve greater losses.
Netherlands 1953- about 10% of Dutch farmland was flooded, 40,000 buildings were damaged and 10,000 were destroyed. 1800 deaths.
Philippines 2013- damages of around $2 billion. At least 6,300 deaths and 30,000 injured.

Question 38

Environmental refugees

Answer 38

Tuluva’s highest point is 4.5 m above sea level.
80% of the population of Seychelles live and work at the coast.
Coral reefs are being destroyed by global warming.
Water supply is limited
Small narrow economies based on tourism and fishing
They have high population densities.

Question 39

Hard engineering

Answer 39

Traditional management approach for coastal erosion is to encase the coastline in concrete, stone and steel. This aims to stop the physical processes altogether or alter them to protect the coast.
Groynes cost £150-250 per meter, sea walls £3000-10,000 and rip rap £1300-6000.

Question 40

Soft engineering

Answer 40

Aims to work with natural systems and processes to reduce the coastal erosion and flood threat.
Soft engineering is usually less obvious and intrusive at the coast and may be cheaper in the long term.

Question 41

Sustainable coastal management

Answer 41

Managing the wider coastal zone in terms of people and their economic livelihood, social and cultural wellbeing, safety from coastal hazards, as well as minimising environmental and ecological impacts. 
Managing natural resources.
Managing flood and erosion risk
Creating alternative livelihoods 
Adapting to seal level rise
Educating communities 
Monitoring coastal change. 
May lead to conflict because:
Natural resources may have to be used less
Relocation may be needed 
Some erosion/ flooding will always occur
Future trends may change, creating uncertainty

Question 42

Integrated coastal zone management

Answer 42

Rio Earth Summit in 1992.
Number of characteristics:
The entire coastal zone is managed
Recognises the importance of the coastal zone to people’s livelihoods
It recognises the management of the coast must be sustainable.
Works with the concept of littoral cells or sediment cells. Each uses a plan called a shoreline management plan.

Question 43

Policy decisions

Answer 43

DEFRA introduced management plans in 1995, there have only been 4 policies for coastal management.
Policy decisions depend on:
Economic value of protected assets
Technical feasibility of engineering projects
Cultural and ecological value of land.
Pressure from communities
Social value of communities.

Question 44

Cost benefit analysis

Answer 44

Used to decide whether defending a coastline is economically justifiable.

Question 45

Environmental impact assessment

Answer 45

Used to identify:
Short term impacts of construction 
Long terms impacts of construction.
It includes impacts of:
Water movement and sediment flow. 
Impacts on wildlife quality.
Possible changes to flora and fauna.
Wider environmental impacts.

Question 46

Winners and loosers

Answer 46

This is inevitable because some areas of protected while others are not.
Local councils have limited resources.

Question 47

Blackwater estuary

Answer 47

Essex.
Area of tidal, salt marsh and low lying farmland. Prone to flooding and coastal erosion, the farmland was traditionally protected by flood embankments and revetments.
In 2000 Essex Wildlife trust purchases Abbots Hall farm on the Blackwater estuary. A 4000 hectare managed realignment scheme took place, which created 5 breaches to the sea wall. This allowed new salt marshes to form inland.
This has a number of benefits:
Owners of Abbots Hall farm got the market price for their farm.
Very high costs of hold the line policy but flood risk was reduced.
Water quality in the estuary improved.
New paths and waterways were created.

Question 48

Coastal management in the developing world

Answer 48

In many parts of the developing world, coastal erosion is often rapid because:
Upstream dams reduce sediment supply
Rapid unplanned development at the coast
Widespread destruction of mangrove forests

Question 49

Soft engineering methods

Answer 49

Beach nourishment- costs £2 million per km of beach but ongoing costs are high and sediment must be sourced sustainably.
Cliff regrading/ drainage- cliff slope angles reduced to increase stability and revegetated to reduce surface erosion. Costs £1 million per 100 m. Can be disruptive.
Dune stabilisation- fences are used to reduce wind speeds. Replanted with marram grass and lyme grass to stabilise the surface. Dune fencing is around £400-2000 per 100m and replanting dunes is about £1000 per 100m. This means it can be very cost effective.

Question 50

Hard engineering coastal defences

Answer 50

Rip-rap- large boulders break up or dissipate wave energy. This reduces wave energy.
Offshore breakwater- forces waves to break offshore, rather than at the coast. This can interfere with longshore drift.
Sea wall- a physical barrier against erosion. Also act as flood barriers. If reflective it can reduce beach volume, and cause the destruction of natural cliff face.
Revetments- absorb wave energy and reduce swash distance by encouraging infiltration. Reduces wave power and can encourage deposition.
Groynes- they prevent longshore drift which encourages deposition, building a wider and higher beach. This can lead to sediment starvation and increased erosion downdrift.