Causes of Flooding

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  • Causes of Flooding
    • Human Causes
      • removal of vegetation - deforestation etc - less interception and infiltration - more surface runoff
      • agriculture - demand for food increases - soil erosion and surface runoff - more sediment in river means reduced capacity and more flood risk
      • urbanisation - impermable surfaces - no infiltration and more surface runoff - enters drainage system, reduce lack time and increase peak discharge
      • floodplain drainage - fertile so good farmland but drying out the wetland destroys habitats and shrinks the area - increasing likelihood of flooding
      • river management - channelisation and straightening the river can increase flood risk e.g Mississippi - levees and man made channels restrict the river, more likely to burst
    • meteorological causes
      • flash flooding - quickly, w/o warning - low pressure systems create intense thunderstorms
      • prolonged and heavy rain - low pressure systems - saturated soil to stop infiltration and increase runoff
      • extreme monsoon rainfall - seasonal change in the direction of the winds as the ITCZ moves north
        • India and SE Asia are at risk to this - extreme rainfall in April-September
      • snowmelt - temperatures increase after winter - increased surface runoff
      • La Nina - warm water and low air pressure to Australia so rainfall increases

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