boscastle flood case study pdf

Case Study – Boscastle Floods

Floods devastate village.

On 16 August 2004, a devastating flood swept through the small Cornish village of Boscastle.

Very heavy rain fell in storms close to the village, causing two rivers to burst their banks. About two billion litres of water then rushed down the valley straight into Boscastle.

Residents had little time to react. Cars were swept out to sea, buildings were badly damaged and people had to act quickly to survive. Fortunately, nobody died – thanks largely to a huge rescue operation involving helicopters — but there was millions of pounds worth of damage.

Physical Impacts

Responses to the flooding, what happened to cause this event.

Flooding On the day of the flood, about 75mm of rain fell in two hours — the same amount that normally falls in the whole of August. Huge amounts of water from this sudden downpour flowed into two rivers, the Valency and Jordan (which flows into the Valency just above Boscastle). Both overflowed, and this caused a sudden rush of water to speed down the Valency — which runs through the middle of Boscastle.

Destruction of houses, businesses and gardens Floodwater gushed into houses, shops and pubs. Cars, walls and even bridges were washed away. The church was filled with six feet of mud and water. Trees were uprooted and swept into peoples’ gardens. The weight of water eroded river banks, damaged gardens and pavements.

Human Impacts There was a huge financial cost to the floods. This included:

• the rescue operation – involving helicopters, lifeboats, and the fire service.
• the loss of 50 cars
• damage to homes, businesses and land
• a loss of tourism, a major source of income for the area

The flooding also had several other key impacts on Boscastle and its inhabitants. These included:

• environmental damage to local wildlife habitats
• coastal pollution caused as debris and fuel from cars flowed out to sea.
• long-term disruption to the village, as a major rebuild project had to be carried out.
• long-term stress and anxiety to people traumatised by the incident.
• John Prescott, the Deputy Prime Minister, and Prince Charles visited members of the emergency services and the local GP surgery, which acted as the emergency centre, in the days following the disaster.
• Prince Charles, who is the Duke of Cornwall, made a large donation to a fund to help rebuild parts of Boscastle.
• The Environment Agency is responsible for warning people about floods and reducing the likelihood of future floods. The Environment Agency has carried a major project to increase flood defences in Boscastle, with the aim of preventing a similar flood happening again.
• We are investing in new ways of predicting heavy rainfall events on a small scale to produce better warnings.

In Pictures

Weather chart

Radar imagery

Fig. 2 shows radar pictures at 12 p.m. (midday)  on 16 August.

The rainfall rate key shows how the colours in the image relate to the rate the rainfall is falling. For example, the red areas indicate that rain is falling at between eight and 16 mm per hour.

A line of very heavy rain starts at about 1 p.m. on the moors close to Boscastle. It remains over the area for about six hours. Rainfall rates of at least 32 mm per hour are being measured.

There is more about  rainfall radar  in the weather section of the Met Office website.

Satellite imagery Fig. 3 shows an animation of satellite pictures from 12 p.m. (midday) to 7 p.m. on 16 August.

The thickest cloud is shown by the brightest white areas on the picture. The pictures show cloud forming over Boscastle at about 1 p.m. and staying there for much of the afternoon.

Further information on other websites BBC News website covering the Boscastle flooding BBC News article – Boscastle one year on

Boscastle 16 August 2004 the day of the flood , 2006, Galvin, 61, 29

Web page reproduced with the kind permission of  the Met Office

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Flood Management Scheme – Boscastle

A flood management scheme following the 2004 floods.

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?

Social 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.

Economic issues

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.

Environmental issues

Biodiversity has improved as have the river habitats. Vegetation in the area is now managed.

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3.13 Case Study - Boscastle Floods (2004)

Flash floods occurred in the valleys of the River Valency and the River Jordan on 16th August 2004.

The village of Boscastle is situated:

in a narrow valley with interlocking spurs which acted like a funnel

in a steep valley which encouraged rapid run-off

on a flat flood plain

in an area where the soil is impermeable clay which does not allow much infiltration

185 mm if rain fell in five hours

The soil was saturated from recent rainfall so no more rain could infiltrate

The collision of winds on a very warm day caused the excessive rainfall (the air mass from the south met the air mass from the south-west and converged on Bodmin which led to towering cumulonimbus clouds. The air was very unstable and the clouds were up to 10 km high).

The natural channel of the river had been walled (for the construction of the B3263 and a pedestrian area) which prevented it from adjusting to a variation in the discharge of the water.

The village had been built on a flat flood plain.

There was no flood control system.

Cars, trees and boulders became stuck under the bridge and created a temporary dam which caused the water to build up behind it.

The sewers and drainage systems were old and small in capacity; they broke and the water that was in the, took an overland route.  

50 cars were swept into the harbour.

The bridge was washed away and roads were submerged under 2.75 m of water, making communication difficult.

The sewerage system burst.

For health and safety reasons Boscastle was declared inaccessible. 

The Museum of Withcraft lost 50 per cent of its artefacts.

Four buildings were demolished and 58 flooded and the High Street was badly damaged.

 The visitors' centre, a clothes shop and two gift shops were badly damaged.

The youth hostel was flooded.

People were in shock and there were concern about hypothermia or being swept away.

There was no power in the village for some time (an emergency generator had to be blown in). 

90 per cent of the economy in Boscastle is based on tourism and there were still three weeks of the summer holidays left; twenty accommodation providers were shut.

Visitors whose cars had been washed away were not able to leave.

A speedy, well-co-ordinated and well-resourced rescue operation ensured that remarkably there was no loss of life. Even by the standards of developed countries, this was outstanding and a tribute to Britain's rescue services.

Emergency workers rescued residents and holiday-makers from a 32 km stretch of the north Cornwall coast.

Hundreds were evacuated from homes, rooftops (120 from rooftops), trees and vehicles.

Seven helicopters from the Coastguards, Royal Navy and RAF were used.

People took emergency shelter in The Rectory, which was on high ground. 

The village was cordoned off by building inspectors for the clean-up operation.

People dug out guttering and removed rubble so that the water could flow away.

Sandbagging was used as a form of defence.

People came to see the catastrophe.

Prince Charles and the Deputy Prime Minister at the time, John Prescott, came to see the damage.

There was a church service to give thanks that no one had died.

The repairs were very costly and time consuming.

There was a huge fund-raising effort to help rebuild the village.

Insurance is now costlier in Boscastle. 

Flood Control and Prevention

The Environment Agency carried out a major investigation.

A £2 million grant was given to Boscastle to help with flood prevention.

No more schools or old people's homes are built in the valley.

The Environment Agency removed debris from upstream, which meant there was more room for the water to flow freely under the new bridge.

A flood defence system (building a flood wall, widening the River Jordan, raising car parks, removing bridges and using relief channels) was planned and is now complete. This also included building a high-arched single-span bridge which would not impeded flood water debris.

Boscastle Floods - 10 Years On

Only watch the first 11.07 minutes of the video.

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Resources you can trust

The Boscastle flood of 2004 – A case study of cause, effect and response

Using the Teachit Geography template, this sorting exercise provides a framework for investigating cause of, effect of and response to the 2004 Boscastle flood.

Extract from the resource: 

The flood on 16 August 2004 in Boscastle in Cornwall was the worst in local memory and an Environment Agency report concluded that it was among the most extreme ever experienced in Britain.

There was a combination of human and physical causes contributing to a series of effects and impacts.  The responses to the flood were both short and long term. Sort statements to show these causes, effects and responses, e.g. loss of businesses, water gauging stations were installed, Boscastle is at the confluence of three rivers, etc.

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