what are the causes and consquences of flooding?
TRANSCRIPT
What are the causes and consquences of flooding?
What are the causes of floods?
• What is a flood?• When do rivers flood?• What factors cause
flooding?• Flooding in Boscastle
case study• What were the causes of
the Boscastle flood?• Homework: what were the
consequences of the Boscastle flood? 2004
Boscastle Flood 2004: Flood factors
• Higher than average rainfall, more rain in one day than normally falls in a month
• Human activity: tarmac’d car park increased surface runoff
• Relief: steep sided valley• Pre-existing conditions: ground saturated by previous
rainfall• Drainage density: small drainage basin, two rivers
(Valency and Jordan) converge, narrow drainage basin, rivers meet in centre of village
• High tide: prevented water leaving the rivers• Soil type: prob. Porous as saturated and collapsed -
landslide
Where will it flood?
• Are areas flood prone?
• Environment Agency flood map
• Rates an area’s risk to flooding
• Includes areas that are defended
Impacts of flooding
• Remember the risk equation?
Risk = hazard exposure + vulnerability - management
Why do the impacts of flooding differ?
• Contrast the impacts of flooding in the UK [Severn and Thames] and SE Asia [Ganges] August 2007