Human activity causing subsidence

• Natural subsidence is the gradual sinking of land

  • E.g due to Isostatic readjustment —> Britain is experiencing Isostatic readjustment
  • Southern Britain is lowered by 1mm a year
  • Whilst Northern Britain is uplifted by 1.5mm a year
  • The UK is pivoting with the South sinking and the North rising
• Human activity can also cause subsidence due to 3 main reasons

  • The weight of Cities
  • Over abstraction of water
  • Vegetation removal
• Weight of Cities - In causing subsidence

  • Cities and built environment can compress sediment leading to subsidence
  • E.g Venice, the cities ground level has been gradually sinking by 1mm a year —> The weight of the city combined with its soft and shifting geological terrain means that sea level around Venice is rising
• Over abstraction of water - In causing subsidence

  • North Jakarta in Indonesia is subsiding at 4.9cm a year —> research found that the main cause of this is overuse of groundwater - as a result of developments in the area
• Vegetation removal - In causing subsidence

  • Bangladesh - exacerbated their vulnerability to flooding through deforestation of their mangrove forest
  • A 100m belt of mangrove forest is estimated to reduce wave height by 40% —> Vegetation absorbs wave energy, reducing wave impact and erosion