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Global issues revision
Flooding case study: Helston December 2012
Catchment size and shape: small catchment area containing small river so
flooding is unlikely. Catchment shape is long and thin so risk of flooding is
Geology types: mainly granite in upper course leading to higher surface
runoff as it's impermeable. Slate in middle/lower course which is more
easily eroded so risk of flooding is increased.
Urbanisation/rurality: flooding occurs most in the urban area of Helston as
surface run off is high due to impermeable surfaces and obstructions in the
river Cober such as arched bridges which slow the velocity of the river.
Rest of river is rural so little flooding as farmland intercepts rainwater.
Valley steepness: areas where valley is steep have higher rates of runoff
this is true of the lower region of Helston where flooding occurs the most.
Precipitation: high rainfall in winter often intense and spread over a long
duration leading to saturated ground and therefore higher risks of flooding.
120 homes in lower streets of Helston flooded, cars left stranded in the
High volume of emergency calls by worried residents so calls had to be
prioritised to life threatening cases
8000 litres of water pumped from St. Johns Street.
Travel around Helston disrupted as roads were flooded.
River levels rose to a high of 2.14m in places, the normal level is between
1.3m and 0.3m
Environment agency pumped water from Loe Pool using 3 temporary pumps
to prevent water backing up the river into Helston
Rescue centre set up to help those displaced by flooding
200 people evacuated from homes at 3am
23 fire engines work to save houses at risk from flooding
Met office issued amber weather warning for heavy rain which stayed in
place until Christmas eve
Severe flood warning issued, 1 or only 4 in the UK
Shelterbox charity provided blankets to evacuated residents
Specialist water crews carried out door to door visits to support local
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Food donated to residents from Helston's farmers market
Temporary homes offered to those who were unable to return to their
homes due to flood damage.
Flood management in terms of channel maintenance which is only carried out
where it's essential to control flood risks.
Investigation of links between land management, run off and flood risk.
Land management schemes considered to reduce flood damage in future.
Public meetings held to discuss approaches to coping with future flooding.…read more