Interaction of Human and Physical Processes (Edexcel GCSE Geography: B (1GB0))

• 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

• 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

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

• 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