Causes of flooding and frequency of flooding in the UK

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  • Causes of flooding
    • Physical
      • prolonged rainfall
        • after long period of rain, soil become saturated. further rainfall can infiltrate ground.
          • increasing surface run off and the discharge = flooding
      • Heavy rainfall
        • means a lot of runoff
          • increases discharge quickly = flood
      • Snowmelt
        • when lots of snow/ice melts means a lot of water goes into river in short space of time
          • increases discharge quickly = flood
      • Relief (how height of land changes)
        • if river is in a steep-sided valley, water will reach river channel much faster bc water flows quicker on steeper slopes
          • increases discharge quickly = floods
    • Human
      • Deforestation
        • trees intercept rainwater on their leaves, which then evaporates.
        • trees take up water from the ground and store it
        • means cutting down trees increases volume of water that reaches the river channel
          • increases discharge, makes flooding more likely
      • Building construction
        • buildings often made from impermeable materials e.g. concrete
          • impermeable surfaces increase runoff and drains quickly take runoff to rivers
            • increases discharge = floods
    • river level increases when discharge increases- high discharge= more water
    • The UK
      • some rivers in the UK have been flooding more recently over the last 20 years
      • 2004, river Valency. Cornwall affected
  • impermeable surfaces increase runoff and drains quickly take runoff to rivers
    • increases discharge = floods

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