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Boscastle Flood :warning: - Coggle Diagram
Boscastle Flood :warning:
Background Info
The catchment area for the Rivers Valency and Jordan is quite small (20km sq) and quite steep (more than 300m tall)
200mm of rain fell in just 24 hours
An estimated 2 million tonnes of water flowed through Boscastle that day
At the peak of the flood, the flow rate for the River Valency was 140 tonnes per second
What Happened?
On the 16th of August, a warm, moist, tropical maritime air mass was approaching Boscastle from the South West. This caused a very strong thunderstorm and heavy rain in the South of England.
Causes of Floods
Steep Valleys can cause flooding because it channels the water into one specific place. In this case it was a river, which meant that all the rainwater from the heavy thunderstorm was suddenly all flowing into the river, causing it to flood
Heavy localised rainfall. 89mm fell in one hour
Saturated ground from previous rainfall
Topography of the land - steep sided valleys which acts as a funnel, channeling the water into the village
Narrow river channels in the village itself
Massive clouds were formed on the Cornish Coast right next to Boscastle
These clouds reached 40,000 ft into the air
The cloud remained stationary for 6 hours, causing 6 inches of rain to fall
Flood Hydrograph
From the Hydrograph, we can see that the lag time is quite short and hat the rising limb is very steep. This shows that the water front the thunderstorm was channeled into the river very quickly, which caused a surge in the river discharge
Timeline
3:30pm - Valency begins to spill over North Bank between the two bridges
3:45pm- Cars in the carpark begin to float. The water is a few inches deep
4:15pm - Flooding on Jordan worsens; main road bridge impassable
5:12pm - Fire service and coastguard declare a major incident
5:23pm - Rescue helicopters begin winching people up from buildings
6:00pm - Flood starts to recede
Impacts
Social
Many cars were destroyed
No deaths but one person suffered from a heart attack
Some people suffered from stress and anxiety
Economic
Property damage was high
Telephone, water, gas and electricity services were all interrupted
The 'Witch Museum' a very iconic attraction in Boscastle was flooded and many items inside were damaged
It took six months for homes to be repaired and people could com back home again
Environmental
Many trees were uprooted and wept away
RRR
RAF helicopters had to be called in to rescue residents
Firefighters joined the rescue operation
150 people were rescued from buildings that were flooded