Interaction of Human & Physical Processes (Edexcel GCSE Geography B)
Revision Note
Written by: Jacque Cartwright
Reviewed by: Bridgette Barrett
Coastal Flooding
Coastal flooding results from a number of factors:
Storm surges: a rapid rise in sea level caused by really low-pressure storms (e.g. tropical storm)
Storm tides: occur when there is a combination of high tide and low-pressure storm
Tsunamis: large sea waves due to underwater earthquakes. The closer to the coast, the bigger the impact
King tides
Sea level rise due to sea temperatures increase from global warming, putting low-lying coastal land at increased risk of flooding
High river discharge after a storm: when combined with a spring tide, water in the estuary cannot discharge into the sea causing a backflow of water and flooding
Global warming and climate change is increasing the frequency and intensity of storms through increased evaporation and rainfall
This increases the height and strength of waves and increases weathering, erosion and mass movement
Erosion may increase which adds to coastal retreat and risk of further cliff collapse
Depositional features such as spits and bars can be destroyed
Impacts are varied from moving people from towns and villages to defences against storm surges and rising tides
Flooding of roads and damage to railways make travel difficult and are expensive to repair
The worst flooding arises from a combination of any of these
The biggest impacts are felt by emerging countries, although the biggest economic cost is are to developed countries
Examiner Tips and Tricks
Areas most at risk for coastal flooding in the UK include:
East Anglia
Towyn and Rhyl, North Wales
Aberystwyth, Mid Wales
Liverpool
Carlisle
Holderness Coastline
Jurassic Coastline
Bristol
Hard Engineering
The aim of any coastal management is to protect the environment but mostly people from the impacts of erosion and flooding
Not all coastal areas can be protected or managed as there are economic constraints
Prediction
Early warning systems allow communities to prepare (evacuate or take shelter) before flooding occurs
Two methods are used to help forecast coastal flooding:
Past records (diaries, newspapers, government/council records etc)
These will identify areas that are at high risk of flooding and their frequency
Modern technology - GIS, satellite and computer monitoring, weather stations (local and national) etc
These allow for forecasting and tracking potential hazard events i.e.
Tropical storms - track the storm's path and associated storm surge
Earthquakes - size and position if underwater and possible tsunami outcome
Both these methods of forecasting help officials to say when and where the event will occur
It indicates the possible strength and scale of the flooding, and the likelihood of damage and death
Prevention
Prevention is about taking action that reduces or removes the risk of coastal flooding
Actions include:
Flood defences
These are built along high-risk stretches of coast
Emergency centres
Centrally placed on higher ground where people can be safe from flooding
Early warning systems
Allows for preparation or evacuation of an area
Education
Informing local people on what to do if and when a flood occurs
Planning
Planning any new development away from high-risk-areas
Designing buildings to cope with low levels of flooding
Elevating buildings so that flood waters can pass underneath
Flood proof buildings with raised foundations (fixed or mechanical)
Reinforced barriers
Dry flood proofing - sealing a property so that floodwater cannot enter
Wet flood proofing - allows some flooding of the building
Buffer zones
Areas of land are allowed to flood before reaching settlements
This allows the energy in the surge to dissipate slowing down the distance the floodwater will travel
It can mean moving people away from the coast which could be controversial
Hard engineering methods
Hard engineering involves building some form of sea defence, usually from concrete, wood or rock
Structures are expensive to build and need to be maintained
Defences work against the power of the waves
Each type of defence has its strengths and weaknesses
Protecting one area can impact regions further along the coast, which results in faster erosion and flooding
Hard engineering is used when settlements and expensive installations (power stations etc) are at risk: the economic benefit is greater than the costs to build
Hard Engineered Defences
Strategy | Description | Advantages | Disadvantages |
|---|---|---|---|
Sea Wall | A wall, usually concrete, and curved outwards to reflect the power of the waves back out to sea | Most effective at preventing both erosion and flooding (if the wall is high enough) | Very expensive to build and maintain It can be damaged if the material is not maintained in front of the wall Restricts access to the beach Unsightly to look at |
Groynes | Wood, rock or steel piling built at right angles to the shore, which traps beach material being moved by longshore drift | Slows down beach erosion Creates wider beaches | Stops material moving down the coast where the material may have been building up and protecting the base of a cliff elsewhere Starves other beaches of sand. Wood groynes need maintenance to prevent wood rot Makes walking along the shoreline difficult |
Rip-rap | Large boulders are piled up to protect a stretch of coast | Cheaper method of construction Works to absorb wave energy from the base of cliffs and sea walls | Boulders can be eroded or dislodged during heavy storms |
Gabions | A wall of wire cages filled with stone, concrete, sand etc built at the foot of cliffs | Cheapest form of coastal defence Cages absorb wave energy Can be stacked at the base of a sea wall or cliffs | Wire cages can break, and they need to be securely tied down Not as efficient as other coastal defences |
Revetments | Sloping wooden or concrete fence with an open plank structure | Work to break the force of the waves Traps beach material behind them Set at the base of cliffs or in front of the sea wall Cheaper than sea walls but not as effective | Not effective in stormy conditions Can make beach inaccessible for people Regular maintenance is necessary Visually unattractive |
Off-shore barriers | Large concrete blocks, rocks and boulders are sunk offshore to alter wave direction and dissipate wave energy | Effective at breaking wave energy before reaching the shore Beach material is built up Low maintenance Maintains natural beach appearance | Expensive to build Can be removed in heavy storms Can be unattractive Prevents surfing and sailing |
Soft Engineering
Soft engineering methods
Soft engineering works with natural processes rather than against them
Usually cheaper and does not damage the appearance of the coast
Considered to be a more sustainable approach to coastal protection
However, they are not as effective as hard engineering methods
Soft Engineered Defences
Strategy | Description | Advantages | Disadvantages |
|---|---|---|---|
Beach replenishment | Pumping or dumping sand and shingle back onto a beach to replace eroded material | Beaches absorb wave energy Widens beach front | Has be repeated regularly which is expensive Can impact sediment transportation down the coast Removing material from the seabed damages fragile ecosystems such as corals and sponges |
Dune regeneration | Planting vegetation helps to create or stabilise sand dunes and beaches Reduces wind erosion | Sand dunes act as a barrier between the sea and land. The wave energy is absorbed, preventing erosion and flooding Cheap method of stabilising dunes | Hard to protect larger areas of coastline cliffs with this method |
Cliff re-grading | The angle of a cliff is reduced to reduce mass movement | Prevents sudden loss of large sections of cliff Regrading can also slow down wave cut notching at base of cliffs as wave energy is slowed | Does not stop cliff erosion |
Managed retreat | Existing coastal defences are abandoned or removed, allowing the sea to flood inland until it reaches higher land or a new line of defences | No expensive construction costs Creates new habitats such as salt marshes | Disruptive to people where land and homes are lost Saltwater damages existing ecosystems Cost of relocation can be expensive Compensation to people and businesses may not be paid |
Sustainable Strategies
There are conflicting views about using a particular type of engineering for coastal defence
Most coastal managers aim to use a range of methods depending on the value of what is being protected
This method is known as Integrated Coastal Zone Management (ICZM)
ICMZ aims to use a combination of methods to best reflect all stakeholder's needs
Coastal strategies
Management of coastal regions is done through identifying coastal cells
This breaks a long coastline into manageable sections and helps identify two related risks:
The risk of erosion and land retreat
The risk of flooding
Identification allows resources to be allocated effectively to reduce the impacts of these risks
The 'cost to benefit' is easier to calculate using coastal cells
Shoreline management plans
Shoreline Management Plans (SMP) set out an approach to managing a coastline from flooding and erosional risk
The plans aim to reduce the risk to people, settlements, agricultural land and natural environments (salt marshes etc.)
There are four approaches available for coastal management, with differing costs and consequences:
Hold the line
Long term approach and the most costly
Build and maintain coastal defences so the current position of the shoreline remains the same
Hard engineering is the most dominant method used with soft engineering used to support
Advance the line
Build new defences to extend the existing shoreline
Involves land reclamation
Hard and soft engineering is used
Managed realignment or retreat
Some or all coastal defences are removed, allowing the coastline to move naturally
Over time the land becomes flooded marshes, effectively protecting the land behind
Most natural approach to coastal defence as it doesn't need maintenance and creates new habitats for animals and plants
However, the land is lost to the sea, which brings conflict, loss of livelihood and saltwater damages existing ecosystems
Mostly soft engineering with some hard engineering to support
Do nothing
Cheapest method, but most controversial of the options
The coast is allowed to erode and retreat landward
No investment is made in protecting the coastline or defending against flooding, regardless of any previous intervention
Decisions about which approach to apply are complex and depend on:
Economic value of the resources that would be protected, e.g. land, homes etc
Engineering solutions: It might not be possible to 'hold the line' for moving landforms such as spits, or unstable cliffs
Cultural and ecological value of land: Historic sites and areas of unusual diversity
Community pressure: Local campaigns to protect the region
Social value of communities: Long-standing, historic communities
Worked Example
Study Figure 10 and Figure 11, photographs showing soft engineering strategies.
Discuss the costs and benefits of soft engineering strategies in protecting coastlines. Use Figure 10 and Figure 11 and your own understanding.
(6 marks)
Do not get distracted and discuss hard engineering, keep your focus on the two soft engineering strategies shown in the figures, and include other soft engineering methods that you have studied
Figures 10 and 11 show beach nourishment and dune regeneration
This is a levelled question and to gain Level 3 you will make sure you discuss the costs and benefits of named soft engineering strategies
Use geographical terminology throughout
Answer
Advantages:
Soft engineering works with nature rather than against it, blends in with the environment and can improve it e.g. adding sand to beaches, doesn’t interfere with processes elsewhere and affect other areas; is more sustainable
Disadvantages:
Areas can just be left at the mercy of the sea, more gentle intervention may not be effective, people can lose their homes and livelihoods
Beach nourishment -
Replaces beach or cliff material that has been removed by erosion or longshore drift. The main advantage is that beaches are a natural defence against erosion and coastal flooding. It usually looks natural and can improve the attractiveness of a stretch of coast. It creates a useful amenity for tourism, it is a relatively cheap option and easy to maintain
However, it does require constant maintenance to replace the beach material as it is washed away. This is particularly the case after winter storms. People may be prevented from using the beach for several weeks during maintenance
Beach reprofiling is the artificial re-shaping of a beach using existing beach material. For example, after winter storms, bulldozers may move shingle back up the beach. The costs and benefits are similar to those for beach nourishment. The disruption caused by reprofiling may have negative impacts on beach habitats
Dune regeneration -
The artificial creation of new sand dunes or the restoration of existing dunes using strategies such as marram grass planting or fencing them off from human impact. Sand dunes act as a physical barrier between the sea and the land. They absorb wave energy and water and in doing so protect the land from the sea. This strategy is considered natural by most people and can produce an attractive amenity for tourists. They may also increase biodiversity, providing a greater range of natural habitats for plants, animals and birds.
However, they can be easily damaged by storms, and it can be time-consuming to plant the grass and maintain the area/it can also deter tourists at this time
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