Coasts

What is equilibrium in relation to the coastal system?

Energy input = energy outputs (over time! Despite the short-term changes). Negative feedback balances energy input and outputs.

What is the difference between a tombolo and barrier beach?

A tombolo is a landform connecting an island to the mainland, formed by deposition of sediment, while a barrier beach is a spit that extends across a bay, joining two headlands, and can trap water behind in a lagoon

Open system

Energy and Matter are transferred

Name the sources of energy in the coastal system

Wind

Waves (constructive + destructive)

Tides (rise and fall of ocean surface)

Currents (general flow of water)

Sediment source

1. The sediment inputs into a coastal system:

2. Rivers

3. Sea level rise

4. Erosion

5. Crushed shells of marine organisms

6. Offshore deposits

Sediment budget

The difference between the amount of sediment that enters the system and the amount of sediment that leaves the system.

Sediment cell

Each cell is a closed coastal system that is self-contained (the processes in one cell wont affect the movement of sediment in another cell).

What is the difference between high energy coasts and low energy coasts?

High energy coasts: destructive waves due to high energy wind, more erosion and transport and mass movement = more wave cut platforms and cliffs. E.g. atlantic coasts of Norway.

Low energy coasts: constructive waves due to lower energy wind = more deposition and transport = more beaches, spits, estuaries. Sheltered and lowland coasts. E.g. mediterranean coast.

Exception= Chesil beach, Dorset. Shingle tombolo from LSD on a high energy coastline (faces south)

Geomorphological processes

Weathering: mechanical, biological, chemical

Mass movement: soil creep, mud flow, landslide, rockfall, rotational slip

Types of weathering

Mechanical: freeze-thaw, ice crystals, wet+dry

Biological: burrowing or roots

Chemical: carbonation (weak carbonic acid), oxidation (iron minerals + oxygen = breaks bonds)

Types of mass movement

1. Soil creep (slow - rock particles rise due to wetting + drying)

2. Mudflow (weak rock w/ pores. Particles forced apart)

3. Landslide (material remains in tact)

4. Rockfall (caused by mechanicl weathering. E.g St Oswalds Bay 2013 = saturated chalk + strata dipping seaward) - scree at bottom becomes input for sediment cell

5. Rotational slip (curved slip plane - permeable rock over nonpermeable rock = buildup of PORE water pressure)

Distinctively marine processes

Erosion (abrasion, solution, hydraulic action, attrition)

Deposition (accumulation faster than removal) - aeolian deposition = by wind (traps, transports, deposits)

Transportation (traction, saltation, suspension, solution)

Factors affecting the rate of erosion

1. Wave energy, fetch and presence of a beach

2. Terrestrial factors: Rock resistance (isle of Purbeck = clay eroding to leave resistant chalk + limestone), Physical and chemical composition of the rock (seven sisters, Dorset), geology

3. Subaerial processes: weathering + mass movement

4. Coastal management: groynes deprive beaches further down (e.g. Bournemouth and Appleton farm), sea walls reflect wave energy elsewhere, etc

Process of deposition

Waves slow after breaking —> water pauses at top of swash —> water percolates through the beach material

Coastal erosional landform examples

1. Cliffs and wave cut platforms

2. Cliff profile features

3. Blowholes and geos

Explain the formation of cliffs and wave-cut platforms

Destructive waves (steep + high energy) break at foot of cliff and concentrate high energy into small area (hydraulic action and abrasion). This undercuts the cliff, forming a wave cut notch. Further undercutting leaves the ROCK ABOVE unsupported, causing it to collapse UNDER GRAVITY. Over time, this repeatedly happens, CAUSING THE CLIFF TO RETREAT BACKWARDS, to create a wave cut platform.

Explain the formation of cliff profile features

Waves refracted due to headland shape, so are concentrated on the sides. Joints widened by HA and abrasion to form a wave-cut notch, which is further widened into a cave, then further undercutting breaks through to the other side of the headland to form an arch. Weathering and gravity cause the arch to collapse, forming a stack and then a stump.

Explain the formation of a blowhole and geo

A joint reaches from the top of a cave to the top of the rock. The joint is widened by hydraulic action, to form a widened joint/crack. (Compressed air by waves released = air expands = shock wave)

If the roof of the cave collapses, a geo is formed - a thin long inlet.

Name some coastal depositional landforms

1. Beaches

2. Simple and compound spits

3. Tombolos

4. Offshore bars

5. Barrier islands

6. Sand dunes

7. Estuary mudflats and salt marshes

Explain the formation of beaches

Constructive waves carry sediment towards shallow water, lose energy and deposit sediment.

Swash - aligned beach = low energy, parallel waves (SAND)

Drift - aligned beach = high energy, waves at an angle, LSD

Flocculation

The process of individuals clumping together to form a heavier particle which sinks to the sea bed.

Explain the formation of a simple or compound spit.

LSD carries sediment along the coast, until a change in direction of coastline. LSD carries sediment a little way, loses energy, deposits it. Area behind = sheltered + salt-tolerant plants grow = salt marsh (AREA OF DEPOSITION).

Spit end curves due to tides + currents + wind direction = recurved spit

Explain the formation of a tombolo

2 methods of formation:

1. LSD carries sediment from mainland to island

2. Refracted waves merge behind island

Explain the formation of bars and offshore bars

Bars: a spit forms between 2 headlands, forming a lagoon behind

Offshore bars: sediment deposited as sea level rises and it the sediment moves closer towards the coast

Explain the formation of barrier islands. What conditions are required for them to form?

2 theories of formation:

1. Offshore sand bars moved towards land

2. Sea levels rose after the last ice age + partially submerged old beach ridges

Required conditions:

• shallow gradient

• Surplus sediment

• Low tidal range

Explain the formation of sand dunes.

Sereal stages:

1. Embryo dune (pioneer species = couch grass)

2. Yellow dune (marram grass)

3. Fixed dune (dead marram = hummus = acidic (and salt alkali = dunes become more acidic further from sea)

4. Dune heath (organic matter = more biodiversity)

5. Dune slack (wetland organisms)

6. Woodland trees (birch, alder, pine - not conditions for oak, so sub-climax reached)

Eustatic change

Change in the volume of the ocean due to changes in climate (ice melting, thermal expansion or ice sheets forming as oceans freeze) or tectonic movements (sea floor spreading).

Global effects

Isostatic change

Vertical movements of the land relative to the sea due to:

• uplift or depression (accumulation or accretion of ice sheets)

• Subsidence (shrinkage of ground as groundwater is abstracted)

• Tectonic processes (plates subducting)

Local effects

Describe the tectonic sea level change over the last 10,000 yrs in the UK

Last glacial period = water stored in cryosphere = sea level was 130m below preset sea level.

As temps rose, ice melted = sea levels rose + has fluctuated over last 4000 yrs but rising since 1930

Coastlines of emergence

From sea level fall

• raised beaches = vegetation = relict cliffs

• Marine platforms (old wave cut platforms exposed)

Coastlines of submergence

From sea level rise

• rias (submerged river valleys)

• Fjords (submerged glacial valleys)

• Dalmatian coasts (valley + coast = parallel)

What TYPE of landscapes form along coastlines?

A mixture of active and relict landforms - reflect different periods of change (can be short and episodic periods, or can be long and gradual changes) e.g. storms or sea floor spreading

How can barrier island be useful?

They form a natural sea defense as waves break over them, lose energy and deposit sediment. But,

Holiday homes can be built on them which stops natural island building up. E.g. 400km along east coast of USA: Office for Coastal Management haad 3 strategies:

1. Beach nourishment $$)

2. Pay compensation to treat

3. Accept building losses

Succession

Sediment accumulating and coastline gradually advancing out to sea

What conditions are required for sand dunes to form?

Conditions for formation:

1. Sand

2. Wide beach @ low tide

3. On shore prevailing wind

4. Obstacle to trap sand

5. Low flat backshore zone

An example of Sand Dune management

Oxwich Sand dunes:

Destroyed by WW2

Management strategies introduced 1973 - 1980, but worked too well and heather started dominating = overfixation = reduces biodiversity

People encouraged to trample, goats introduced, dune slacks dug up (kick started willow)

Outline processes of mass movement at the coastline. (4 marks)

There are different routes to credit depending upon the chosen type of mass movement eg

• Mass movement is the gradual or sudden movement of sediment downhill under the force of gravity (1).

• Rockfall occurs typically where weathering causes pieces of rock to break away from a slope of cliff and fall to the bottom (1). Some may link this to scree (d). Rock slide is a similar concept but involves the collapse of an area along a joint or bedding plane (d).

• Some may legitimately consider solifluction, the slow movement of soils downslope in permafrost areas (1). The process here is linked to the melting of surface layers of soil in the active layer (d) which are then lubricated and move under gravity, usually more slowly (d). The movement is always along the plane where the active layer meets the permafrost (d).

• Also allow rotational slip in the same regard (up to 4 marks for clear outline of process).

To what extent do natural processes account for the changes in a local scale coastal landscape that you have studied? (20 marks)

AO1

• Eustatic, isostatic and tectonic sea level change.

• Recent and predicted climatic change and potential impact on coasts.

• Case study(ies) of coastal environment(s) at a local scale to illustrate and analyse fundamental coastal processes, their landscape outcomes as set out above and engage with field data and challenges represented in their sustainable management.

AO2 •

• There are essentially three potential lines of response depending on the focus of the coastal landscape:

• Some will argue that natural processes are having a substantial effect on shaping their chosen coastline. A combination of erosion, deposition and weathering are likely to feature along with associated landscape development and or threat to local communities. Case studies such as Holderness or specific known erosion or depositional landscapes may feature. In this regard the main change is likely to be the impact of process on the landform / landscape development which if unchecked will lead to significant changes in the coastline.

• Others will challenge the assertion of the question and take the view that it is climate change and associated sea level rise which accounts for major aspects of change at the chosen local scale case study coastlines. Changes to lowland coastlines and estuaries are likely to feature in this regard. Some may link this to isostatic adjustments as well as eustatic change. There may be reference to the Dalmatian Coastline or raised beaches in Scotland for example. • The third approach will be to argue that it is human interference which remains the dominant force shaping coastlines. Such arguments are likely to focus upon the impact of management decisions and policies as the dominant force. Support may consider some assessment integrated coastal management or shoreline management plans. Credit any other valid approach. Evaluation should be based upon preceding content.

With reference to a coastal landscape from beyond the UK, assess the role of human intervention in shaping the physical environment. (20 marks)

AO1

• Case study of a contrasting coastal landscape beyond the UK to illustrate and analyse how it presents risks and opportunities for human occupation and development and evaluate human responses of resilience, mitigation and adaptation.

• Human intervention in coastal landscapes. Traditional approaches to coastal flood and erosion risk: hard and soft engineering. Sustainable approaches to coastal flood risk and coastal erosion management: shoreline management/integrated coastal zone management.

• Recent and predicted climatic change and potential impact on coasts.

AO2

• Expect many responses to consider coastal management as part of the intervention in shaping coastlines. Case studies are likely to focus on The Sundarbans and / or Odisha though others may feature.

• Bangladesh lies, in large part on the Ganges Delta. This low-lying land is highly susceptible to flooding and erosion. Sea level change is a serious threat to the viability of coastal Bangladesh. Without concerted, integrated and consistent action, Bangladesh’s existence would be under serious threat.

• Expect to see reference to Integrated Coastal Zone Management (ICZM). This is a holistic approach which brings together all stakeholders. It sees the whole coastline as one unit rather than the more dated approach which historically failed to see that actions in one part of the coast could have devastating impacts elsewhere.

• Bangladesh has the combined issues of land subsidence, sea level rise and a growing population occupying ever more marginal land.

• The Bengali people have years of experience of adapting to changing environmental conditions caused by shifting river channels, land creation and erosion, and the impacts of floods, cyclones and storm surges. The country’s government, too, has long experience of managing change, including measures to cope with natural disasters. Bangladesh is not helpless, therefore, against coping with sea-level rise. A number of interventions are being used to counter foreseen impacts of sea-level rise during the 21st century.

• The country aims to maintain freshwater flow to western parts of the Ganges Tidal Floodplain in order to prevent the salt-water front from moving further inland. The most direct method has been to divert additional water from the Ganges River down the Gorai-Madhumati River by means of a barrage across the Ganges in Bangladesh.

• Embankments have been raised and strengthened as sea-level rises.

• Bangladesh has been experimenting with raised mounds or banks on which to grow crops. This adaptation is designed to retain farmland in the event of a saltwater ingress.

• In the Meghna estuary, land reclamation is providing new land for cultivation and providing fresh water for domestic use.

• In rural areas, work has been undertaken to raise house plinth levels above the highest predicted storm-surge levels and increase cyclone shelter capacity as population grows.

• For Chittagong and Cox’s Bazar, the two major coastal cities most exposed to sea-level rise and to storm surges, the creation of artificial raised land using material from nearby hills is being investigated.

• In the longer term, too, investigate the practicality of constructing barriers across river mouths in the south-west to prevent salt-water intrusion, as in The Netherlands.

• Assessment is likely to consider cost benefit as well as effectiveness of such strategies. Any assessment is permissible provided it is based upon preceding content.

Outline factors leading to the formation of fjords. (4 marks)

• Fjords are an example of coastal landforms of submergence (1). They are primarily a product of glacial erosion (1). As glaciers advanced towards coastal locations in Norway for example, they carved out vast glacial troughs (1), through processes such as abrasion and plucking (1) (d). A combination of localised isostatic re-adjustment and global eustatic sea level change has led to the flooding of these valleys (1).

• An example of Sogne Fjord in Norway (1).

• Reference to interglacial period is a factor leading to formation to fjords(1)