Coverack Flood 2017

Flash flooding shocks Coverack in middle of summer

In News by Ambiental Environmental Assessment

Flash flooding shocks Coverack in middle of summer

A flash flood swept through the Cornish Village of Coverack last month filling homes with water and causing extensive damage. Through analysis, Ambiental’s flood maps were successful in predicting the flood hazard at this location and modelling the impact the flood had on properties.

Floodwaters, as high as four feet in some places, poured through the village and over the sea wall below. Rain and hailstones as wide as 50p pieces lashed the town as the storm lasted an hour and a half leaving the main road underwater with an almost instantaneous flood that cut the village in half.

The main road has been completely destroyed by the volume of water surging over it, meaning residents could not get in or out of the village. Some 50 properties have been affected, with the cost of repairs and insurance already estimated at more than £1m, given the structural damage to roads and buildings in the area.

The flash flooding in Coverack is the worst to hit Cornwall during the summer since the Boscastle disaster in 2004. The storm was part of a series of highly localised systems that crossed the UK on July 18th. Some areas received more than two weeks’ worth of rain in one hour. The heaviest recorded by the Met Office was at Reading University where 36mm fell in the evening.

Data obtained from the Centre for Ecology & Hydrology’s (CEH) COSMOS-UK soil moisture monitoring station on Goonhilly Downs just 7km to the west of Coverack – shows the rainfall that led to the flooding was very much localised.

The CEH rain gauge recorded just 0.12mm on the same day, which is corroborated by soil moisture data which shows no significant increase.

John Curtin from the Environment Agency tweeted an image the following day confirming just how localised the most severe rainfall was within the same storm system:

Coverack storm

During and after flooding events Ambiental is able to use information from the media and government sources to assess the predictive accuracy of our flood map products. An analysis was run on UKFloodMap4™ to establish if the pluvial flash flood layer had predicted a hazard at this location. The data showed a clear flood hazard flow path at the affected location which matched with observations from the event. Our sister company, Ambiental Risk Analytic’s UK FloodScore™ was also shown to have accurately predicted the number of properties affected.

This data validation exercise demonstrates that having high precision flood hazard data is vital for insurers, governments and asset managers wishing to identify at risk locations. 

This analysis also highlights the importance of not just relying on fluvial flooding (from rivers) and tidal flooding (from the sea) as the risk of pluvial flooding (from intense rainfall) affects many more areas which would otherwise be missed.

With extreme events such as this flood in Coverack predicted to rise through climate change the need for a dependable view of flood risk is ever more necessary. Ambiental has recently developed an innovative new product in response to the unpredictable nature of a changing climate. Our  FloodFutures™ datasets have been developed in collaboration with Landmark Information Group and enables easy interpretation of flood risk resulting from climate change. To find out more about Ambiental’s products visit our website and contact us.

Steven Brown Ambiental Associate

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