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  • Created by: Rosa
  • Created on: 27-04-13 17:14

Dynamic nature of Coasts


  • As wind blows over the ocean friction occurs and energy is transferred creating waves.
  • Stronger the wind the greater friction making waves higher & more powerful
  • Waves move in a circular motion
  • As they move to shallower water the frictional drag of the seabed slows down the base of the wave making it increasing eleptical in shape which reduces wavelength and increases wave height until the top of the wave breaks due to it moving faster that the base
  • Longer fetch (uniterrupted water over which waves are generated) bigger waves (PAGE 48 FIG 2.2)

Constructive Waves

  • Wavelength are long , wave height less than 1m- high swash, little backwash-beach develops creates berms  (swash = pushes sediment up beach)-

Destructive Waves

  • result from storms- wavlength is short but waves are high, so breaks from high creating energy which cannot be absrbed easily be beach - powerful backwash removes sediment
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Dynamic Nature of Coasts

Tides = caused by gravitational pull of the moon. Moon pulls water towards it causing a swell which creates a hightide. Twice a month sun , moon and earth are aligned causing high tide - can be predicted

Storm Surge (high onshore winds and tides combine to give unusually high sea levels)- they are created when:

  • high tides
  • strong onshore winds creating high levels of wave energy
  • low pressure weather systems (allowin sea to expand)

Can cause extreme flooding 

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Coastal Processes

MARINE EROSION (action of sea on coastal landform)

Hydraulic Presure = breaking waves exert a force (up to 40 tonnes) on to cliff faces , they force air into joints and cracks in the cliffs , this compressed air has the power to loosen and breeak away pieces of rock

Abrasion/corrasion= waves pick up sand particles and pebbles and hurl them at the cliff face - it gouges at the cliff

Attrition = rocks and pebbles colliding with eachother as moved by waves , which reduces size of beach material and increases roundness and smoothing away rough edges


Corrosion/Solution = saltwater evaportaion from sea-spray leads to the growth of salt crystals in rocks, as they develop they expand forcing rocks to disintergrate especially limestone

Wetting/drying= rocks prone to expansion and contraction as become wet and dry out- so becomes weak and erode easily

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Human Activity/Mass Movement

Human Activity = leasiure and recreation can put pressure on coastal environmnts . Human erosion of cliff-top paths weaken rocks structure  and removal of vegetation leaves rocks surfaces more prone to weathering and erosion

Mass Movement= occurs due to wave action weakening the base of the cliff and sub-aerial processes (processes active on the face and top of cliffs), they include weathering processes and effects of rainfall erodign cliff surfaces or weakening rocks by percolation (water soaking into rocks). Resistant rocks create rockfalls due to undercutting and corrosion and wetting and drying . Landslides and slumping associated with weaker rocks  and are triggered by heavy rainfall. Ground becomes saturated due to the extra weight , slope , and lubrication.

Rock type and structure can have a significant imapact on coastal landforms , more resistant rocks such as chalk and limestone erode more slowly and produce cliff and headland features , as weaker rocks such as clay have less sturctual strength and erode easily. Coasts were rock type runs parallel are called concordant coasts and are often straighter coastlines. Not in straight lines calles discordant and produce headlands and bays












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Landforms associated with resistant rocks - headlands = beacuase of the position of headlands they are under constant attack from marine processes.and results in ditinct land features, stack , stumps , cave (Page 53 fig 2.9)

Landforms associated with weaker rocks- landslides are prone in these areas and thy happen when the force of gravity acting on the slope is greater than the resitant strength of the rocks. Clay coastlines are prone as it becomes unstable when wet.

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Features of Coastal depostion

Swash-aligned beach= when waves approach the coastline parallel to the beach, swash and backwash move sediment up and down the beach , creating a stable straight beach. During  storm conditions sediment can be moved out to sea creating sand or shingle bars

Drift-aligned beaches = when waves approach the coastline at an angle and sediment is moved along the coast by the action of long-shore drift - can be slowed by groynes, they allow beaches to build up and become wider however they can starve other beaches.

Spits and Bars= ridges of sand or shingle that have been deposited by the sea, often are created when there is a change in the direction of the coastline or a break in the land where a river enter the seas. At these points material is deposited in the same direction as the coastline. Material is shaped by the wave action , a spit is joned to land at one end and a recurved tip is the other end in the sea. A bar is formed when a spit extends across an opening and connects two headlands. A tombolo where a deposition of sediment joins an island to a mainland-

Hurst Castle Spit (hants)- shingle ridge developed due to longshore drift in Christchurch Bay- due to change of direction in coastline - spit 2km out from coastline-curved end due to wind and tidal currents







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Coastal System

Needs to be a balance of inputs (deposition by rivers , weathering and erosion of cliffs) and outputs of sediment(sediment loss to open sea, sediment removed by human intervition), if there is a balance there is equlibrium.

  • Positive Sediment Budget - beaches are developping and are stable
  • Negative Sediment Budget- loss of beach material
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Managing Coastal Areas

Why do coastlines need to be managed :

  • many people live nerar the sea without protection millions pounds of property would be lost
  • Rising sea levels mean coastal areas will be flooded
  • if areas are flooded they have important industrial areas and ports with jobs
  • Costal tourism is a massive industry and need to be protected (and anmals)

Shoreline Management Plan - it examines the risk associated with costal processes and presents a policy to manage the risks. In the sub-divided cells the following things have to be considered:

  • identify the economic and environmental assests that would be affected by flooding
  • propose a coastal defence plan
  • whether to hold the line (mainain existing defences) or advance the line (build new defences) , managed retreat (allow land to flood with careful monitoring) or no active intervention (no investment in providing any management)

Intergrated Coastal Management - is a method of managing not only shoreline but also the whole coastal zone it was set by the EU,'environmentally stable, economically fair, socially responsible, culturally sensitive'-alongside SMP

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Managing Coastal Areas

Hard Engineering ; 

  • sea walls - curved (reflect wave) , straight concrete structures
  • groynes- wooden or concrete structures designed to break wave and slow LSD
  • Cliff drainage - piped drainage in cliffs to prevent landslides
  • Rock Armour - large rocks placed at the foot of sea walls - absorb wave energy
  • Offshore Bars - rows of boulders built up offshore to break waves before the beach

Soft Engineering : 

  • beach repldnishment- pumping sand or shingle back on beach to replace material 
  • fencing/hedging - preseverse beach by reducing amount of sand being blown inland
  • replanting vegetation- planting grasses or salt-resistant plants help to stabilise
  • beach recycling - moving material from 1 end of a beach to other to counteract LSD 
  • ALL METHODS try to work with natuarl processes in area - less money - environmentaly friendly 

Managed Retreat - abandoning exisiting coastal defences and allowing sea to flood inland. Allows low lying area to become salt marshes and is a natural defence  - good habitiat - not expensive - (farmland or where few houses) 

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CASE STUDY-Multi-engineered Coastline - Vetnor to

Geology in this area is a mix of chalk , green sand and clay and has no real unifromity- has a range of landslide features: 

  • rotational slumping - creates linear benches 
  • mudslides where clay is exposed & vunreable to movement - wet conditions
  • rock falls and coastal landslides where exposed areas of cliffs not protected from wave attack 

Coastline is vunreable to wave attack due to the following reasons:

  • storm conditions Atlantic waves from south-west create a powerful storm surge over 1m higher than normal levels 
  • limited supply of drift material in area so beaches are narrow or dont exist and offer little protection for cliifs from wave attack 
  • during storms waves pick up gravel and atttack the cliffs or exisitng coastal defences  
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During the last 25 years a no. of heavy engineering schemes have been put in place to protect whole of the coastline between Vetnor and Bornchurch- the main one being a sea wall - environment impacts have been considered such as habitats however it is clear that hard engineering options are the only viable option to protect area from wave attack. 

Wheelers Bay; 

  • slope stabilisation - area of previous landslide
  • straight edged sea wall 
  • rock aromour - large boulders places in front of sea wall 
  • metal reinforcement - backed by concrete
  • concrete tetra pods infront of sea wall 
  • lipped sea wall to referact and reflect sea wall 
  • cliff drainage
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Southampton is one of the best natural harbours as , it is sheltered from channel storms ,deep water channels for large ships and is surrounded by flat land. 

Many conflicts can arise , such as at Dibden Bay the company ABP have put forward plans to construct a new container terminal - wanted this site in Southampton as: 

  • Southampton location on South Coast is on a major international route from Europe to rest of the World 
  • it can be accessed by rail and road by much of the UK without going through London
  • helps southampton and reigon with economy and remains internationally competive

Key feature of plan:

  •  deep water Quay of 1.8km of length - and a deep water channel connecting to exisiting deep water
  • 202 hectare port handling area for container transfer , storage and distribution 
  • 1.4km of a 10m wide access road linking the terminal to A326 

Project also proposed some environmental improvements :=- construction of tidal creek and conservation area - interdidal recharge of Dibden Bay- 3.8 hectares open space
ABP produced staements saying they could deal with impacts - employment , transport , conservation and nature and pollution however there was a massive protests including local residents , group was formes 'Residents Against Dibden Bay Port'- RSPB against it - wildlife main problem - not build due to environment impact

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Fawley Oil Refinery = The largest refinery in the UK , it employs 3000 people and handles 2000 ships and 22 million tonnes of crude oil & has 1.5km dock frontage , however there are environmental impacts - loss of salt marsh SSSI , liquid waste can be up to 30 degrees which affects sea temp. , there is metal pollution (lead . mercury). 

In Southampton there is pressure on the water due to Residential expansion of Southampton and surrounding villages which is happening rapidly. - also pressure of sailing and leisure activiities too. 

Environmental impacts of industry sewage , including: 

  • 300m litres of treated sewage released in to the solent
  • more housing = more sewage
  • raw sewage threat to swimmers and eco-systems (clams and oysters)
  • POLLUTION - oil spills - 20 tonne spillage in 1989 on calshot spit + solid waste 

Dibden Bay is now a SSSI and is a Protection Area , its of wildlife area of national and international importance- both habitat and feeding ground for species  

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Florida is known as the 'sunshine state', in the USA as it has tropical climeate (especially in Florida Keys). High temperatures and cool sea breezes make it an attractive place for resident and holiday makers. Florida has fastest growing GDP of any US State (7% between 2000 and 2006), and has the 3rd fastest rate of populationg growth (9.7 million in 1980 and 19 million in 2007). Comfortable Climate ,economic oppurtunities , high living standards and leisure activities are major attractions for working population as well as a magnet for second home owners and retired.  Florida has many tourist attractions including internationally known theme park such as Walt Disney and Universal. It attracts millions of visitors and tourism is the largest sector of employment. However due to this there have been a number of pressures on coastal areas: 

  • algae blooms (red tide) due to water pollution 
  • damage to fragile marine eco-systems linked to tourism 
  • sediment loss due to dredging for construction materials 
  • urbanisation of coastal with increasing demand for space
  • vunreability to flooding as sea levels rise 

Miami - 5th largest Urban Area in USA - called 'cruise capital of the world'- linear city and inland growth is limited due to Everglades National Park- centre financial headquaters to Disney , American Airlines- most of built environment is less than 10m above sea level - main part of city on shore such as Miami Beach 

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Monks Bay - cliff failure resulted from a combination of high energy destructive waves and high rainfall during storms. As a result there are many coastal defences 

  • construction of off shore break water 
  • six rock groynes 
  • beach norurishment 17,000 cubic metres of sand and gravel
  • 25,000 tonnes of Swedish Granite - rock wall & tetra pods 
  • installing land drainage 

Wheelers Bay - due to landslides property on cliff cannot be sold- a scheme to stabalise slope 15,500 tonnes of Norweigan granite was placed at were exisiting sea wall was to reinforce it & land drainage- 1.6 million - propert value of houses have now recovered

Western Cliffs - below western Vetnor consist of blocks of chalk brought down by landslide activity have acted as a natural sea defence for the houses behind. However high-energy waves and sub-aerial processes have been removing chalk and there is a danger that lateral erosion could reactivate landslides- limestone from Somerset has been brougth in to construct a 700m long rock revetment along the base of the cliffs- Upper Greensand natural chalk cliffs have been reinforced by construction of limestone rock groynes at 100m intervals at base of the cliff 

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