Boscastle Cornwall Flood Case Study

Described in guidebooks as ‘absurdly picturesque’, the village of Boscastle has for at least 150 years attracted significant tourist numbers, drawn in largely by the striking physical setting of the village. The lower village and harbour sits within an Area of Outstanding Natural Beauty, a Conservation Area and the lower valley is largely in National Trust ownership. Changing patterns of use and development over the centuries have created a complex, characteristically Cornish, port settlement.

In 2004 a catastrophic flood tore through the village destroying 5 buildings and damaging 47 others. Remarkably no life was lost. Following this disaster the challenge was to reshape and enhance Lower Boscastle’s flood protection, creating a safe environment that maintained the community’s sense of place and identity.

Nicholas Pearson Associates (NPA) was appointed as landscape architects to the project team to work with Halcrow Group Ltd to deliver a flood alleviation strategy in a way that was responsive to this sensitive and heavily protected landscape. A full Environmental Impact Assessment was undertaken with NPA providing concept design inputs, consideration of high level design alternatives and preparing a Landscape and Visual Impact Assessment of the preferred solution. The project team worked within a challenging brief defined jointly by the Environment Agency, North Cornwall District Council, the National Trust and the local community.

The design process consisted of three main steps:

1) Identification of the distinctive characteristics of Lower Boscastle: the village can be divided broadly into three character areas. Landscape strategies were devised for each character area. Achieving flood alleviation, landscape conservation and landscape enhancement together was the overarching priority.

2) Assessment of the flood damage on ‘micro’ scale landscape elements: the condition and value of physical elements that remained post flood were assessed in order to understand the damage caused and what items retained historical integrity. This phase drew upon earlier character studies, photographic evidence, discussions with local people and historic map studies. The assessment showed for example that the constrained river channel had been wider in places during the eighteenth century, and over time the channel had been in filled and riverside land had been built on to allow port activities to expand. The scheme allowed for the restoration of some lengths of bank to their earlier positions.

3) To review and tailor the engineering design options to the location: A significant element of the process was to define how much change could be tolerated by the protected landscape. This understanding of acceptable change influenced the development of design options. The most significant design interventions were directed towards those parts of the environment that had the greatest capacity to accommodate change or which would benefit most from enhancement whilst coping with flood flow predictions.

All proposals were evaluated in terms of their potential for beneficially influencing the overall sense of place in order to protect the historic integrity of the village.

The widening and deepening of the river channel, a key element in increasing the capacity of the river to handle flood flows was facilitated through the preparation of a river walling design guide that identified and retained surviving, authentic stone walls, defined vernacular wall styles and walling techniques to be used. It also guided the selection of appropriate materials, stone sizes and colours to avoid any possibility of losing the key sense of detail, variety and authenticity.

The main car park access was improved and the parking area was moved away from the river edge incorporating the design of over land flow routes and vehicle escape routes, reducing the risk of flooding and improving the riverside environment. This improved river habitat and increased biodiversity potential through the use of native planting, meadow restoration and hedge replacement has been established on reinforced embankments beside new riverside footpaths.

The final element of the project was to reconnect the east and west banks by the harbour with a new foot and vehicle bridge to replace the one washed away by the flood. Considering the potential future flood flows, the picturesque protected setting and significant stakeholder influence, a number of options were developed and tested through the preparation of photomontages. The favoured bridge design, now complete, appears on post cards of Boscastle and has been recognised for the quality of its design.

Approximate Map Location


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Boscastle Floods

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

Floods devastate village

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

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.

Responses to the flooding

  • 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.

What happened to cause this event?

Weather map

Fig. 1 shows the weather map for midday on 16 August.

The wind is blowing anticlockwise about the low pressure area, so the air is arriving into Boscastle from a south-westerly direction. It is a warm and moist tropical maritime air mass.

The line labelled (known as a trough line) caused very heavy rain and thunderstorms. A trough is an area of localised rain and thunderstorms. A line of convergence formed near the coast line, where air moving in almost opposite directions collides, this helped to increase the rate of ascent and produced very heavy rain.

There is more about Key to symbols and terms in the weather section of the Met Office website.

Radar imagery

Fig. 2 shows an animation radar pictures from 12 p.m. (midday) to 7 p.m. 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

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