Coastal Flooding (Edexcel IGCSE Geography): Revision Note

Causes of coastal flooding

• Coastal flooding results from several factors:

  • Storm surges – a rapid rise in sea level caused by really low-pressure storms (e.g. tropical storms) 

  • Storm tides - occur when there is a combination of high tide and low-pressure storm

  • Tsunamis – large waves resulting from underwater earthquakes

    • The closer to the coast, the bigger the impact

  • King tides

  • 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

  • Sea level rise due to global warming

    • The standard height of the ocean rises with rising sea levels

    • Normal tides and waves now reach further inland than in the past

    • Low-lying coastal areas that were above the high tide line may now regularly flood with water from the sea

    • Floods are worsened by higher sea levels and storm waves because water starts at a higher position and will travel further inland

• These may all lead to coastal defences being overwhelmed and the flooding of coastal areas

• The worst flooding arises from a combination of any of these

• The biggest impacts are felt by developing and emerging countries, although the greatest economic cost is to developed countries

Prediction & prevention of flooding

Prediction

• Early warning systems allow communities to prepare (evacuate or take shelter) before flooding occurs

• Two methods are used to help forecast coastal flooding:

  • Records of past events (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

    • Tracking a tropical storm's path and associated storm surge

    • Monitoring tectonic activity to track any potential tsunamis

• 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 floodwaters can pass underneath

    • Floodproof buildings with raised foundations (fixed or mechanical)

    • Reinforced barriers

    • Dry floodproofing – sealing a property so that floodwater cannot enter

    • Wet floodproofing – 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