Boscastle Flashcards
when did the flooding occur?
16th August 2004
where is it located?
on the coast of cornwall at mouth of the river valency, in the south west of Britain
on which day did the meterological agency forecast heavy rainfall?
16th however couldn’t say where it would develop
how long for and how much rain dropped?
200mm in around 24 hours
how did the storm occur?
from a large depression of low pressure over the atlantic . warm air from the sea met with warm sunshine producing huge clouds
what type of rainfall occurred?
convectional
how does convectional rainfall occur?
warm moist air rising and cooling causing water vapour to condense and rain to fall
how much water flowed through Boscastle?
2 million tonnes
what was the peak discharge?
100 cumecs
how long was the lag time?
3 hours
what type of rock is in the area?
Millstone grit - sandstone however was impermeable due to antecedent conditions
size and shape of the drainage basin for the river valency?
small and round around 30km^2
physical factors?
topography - steep
high relief
antecedent conditions 50mm in 2 hours early afternoon
Human Factors?
cars - one trapped under bridge water build up
little flood defences
land use - urbanisation
how were local ecosystems affected?
debris from buildings may have damaged the ecosystems
