Why the Boscastle flood scheme required?
On the 16th August 2004, a devastating flood swept through Boscastle, a small village on the north Cornwall coast.
Very heavy rain fell in storms close to the village, with over 60mm of rainfall in two hours. The ground was already saturated due to above average rainfall during the previous two weeks. Combined with this the drainage basin has many steep slopes and there are areas of impermeable slate that led to rapid run-off. Boscastle is at the confluence (where tributaries meet) of three rivers – Valency, Jordan, and Paradise. About two billion litres of water then rushed down the valley straight into Boscastle within a short space of time causing the rivers to overflow. Additionally, the deluge of water coincided with a high tide.
As the flood happened so quickly local residents had little time to react. Cars were swept out to sea and buildings were badly damaged. Thankfully, no one lost their lives, which is largely due to a huge rescue operation involving helicopters. Million of pounds worth of damage was caused by the flood.
What was the management strategy?
In 2008 a flood management scheme for Boscastle was completed. The solution included both soft and hard engineering strategies.
The Environment Agency has made a considerable investment in flood defences in Boscastle to help prevent a similar flood happening in the future. Working with professional partners, more than £10 million of improvements were carried out. This included widening and deepening the Valency River, and installing a flood culvert to improve flow in the Jordan River.
River Valency Flood Management Scheme
The Met Office and Environment Agency have formed the first of several working partnerships, the Flood Forecasting Centre. Combining expertise in weather forecasting and hydrology has helped to prepare communities for flooding during times of extreme weather.
At the time of the floods, the operational forecast model had a resolution of 12 km, which was too large to be able to represent such a small scale collection of thunderstorms. Since 2004 the Boscastle case was re-run with a higher resolution research model which proved able to resolve the line of thunderstorms with much more accuracy and detail.
What are the social, economic and environmental issues?
The rebuilding projects and construction of flood defences took several years which meant the lives of local people were disrupted for sometime. The risk of flooding has been reduced making Boscastle safer. The defences would not protect against a flood the same size as the one in 2004. The new bridge is not popular with local people as it is out of character compared to the rest of the building.
The risk of flooding has been reduced. Therefore, there is less risk of damage to property and businesses. The flood-defence scheme cost over £4 million. However, the scheme could have been significantly better, though some options were too expensive.
Biodiversity has improved as have the river habitats. Vegetation in the area is now managed.