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The Boscastle Floods 2004
 
Metrorological Phenomena
Topography
Rescue Efforts
Social Consequences
Economic Consequences
Environemntal Consequences
Redevelopment
Videos
 
         
 
Timeline

Click on the timeline to download a larger version. Source

 
Meteorological Phenomena
Analysis Chart
Synoptic situation for 1800 GMT on Monday 16 August 2004.
 
Radar Rainfall Accumulations
 
Rainfall Graph
Graph below showing 15 minute rainfall totals for Lesnewth TBR (Tipping Bucket Rain Gauge).
 
Met Office Radar
 
  • At midday, on the 16th August 2004, heavy, thundery showers had developed across the South West, these were the remnants of Hurricane Alex which had crossed the Atlantic. Bands of showers aligned themselves with winds that had converged along the coastal high ground around Boscastle, creating Cumulonimbus clouds 12192 metres high and kept them stationary for many hours. Source
  • The chance of such heavy rainfall in any given year was around 1 in 400. Source
  • A string of slow-moving thunderstorms caused localised extreme rainfall over north Cornwall. The rain was extreme in both its intensity and duration: up to 200 millimetres fell in 24 hours. Source
  • The storms grew out of a large depression (low pressure) area that dominated the eastern Atlantic that day. It had sucked in pulses of warm, moist tropical air, including the remnants of Hurricane Alex. Source
  • The moist air blowing in from the sea in the prevailing south-westerly wind and a morning of warm sunshine combined to produce clouds over the north Cornwall coast. Some of these grew in size and spawned ‘stormlets’, individual small thunderstorms. Source
  • The storms were small in size but produced very intense rainfall. That intensity came from the storms’ high moisture content and their ‘uplift’, the process of warm moisture-laden air being driven upwards, causing rain to fall as the air cools. Source
  • The storms were channelled along the coast by what weather experts call a 'strong line of convergence', a line where a moving airflow meets an opposing one and the air is forced upwards. As the south-westerly wind blew over the land, friction from the rough surface slowed the wind and swung it from south-west to south-southwest. Source
  • This south-southwesterly wind pushed up against the prevailing wind at the coast and created strong uplift. The uplift may have been reinforced by higher air temperatures onshore, caused by the earlier sunshine heating the land - air rises as it heats. Source
  • Storm showers along the whole north Cornwall coast all started at about the same time, 1pm. It is thought likely that this synchronised timing was due to the convergence along the coast. The storms moved slowly up the coast, shedding their load of thousands of tonnes of rain. Source
  • It’s estimated that two million tonnes of rainwater flowed through Boscastle that day. Source
 
Topography
Boscastle Topography
 
  • It has been estimated that the Boscastle valley’s catchment area exceeds 23 square kilometres, spanning inland to Bodmin Moor where many small rivers spring.
  • The steep sided valleys that converge down to the sea, known as “flashy catchments”, act as huge funnels and can produce true flash floods after a sudden cloudburst or prolonged heavy rainfall. Source
  • During the afternoon of the 16th,an incredible amount of rainwater fell, conservatively estimated to have been over 1422 million litres of rain in just 2 hours, that’s over 197500 litres falling per second. At its peak, nearly 25mm had been recorded in a 15 minute time span, that’s over 632000 litres falling per second, the equivalent of 100 tonnes or 21 petrol tanker loads flowing through Boscastle every second! Source
  • Consultants HR Wallingford concluded in their technical study that land use changes would have had little impact on the severity of the flooding in the centre of Boscastle. Source
 
Rescue Effort

Helicopter Rescue

 
  • 7 helicopters airlifted 100 people (including 6 firefighters) to safety. Source
  • 29 out of the 31 Cornwall County Fire Brigade stations were involved in the incident.They remained at Boscastle for 7 days, assisting in the clean-up operation. Source
 
Social Consequneces
  • Around 1000 residents and visitors are believed to have been affected in this devastating event. They witnessed the largest peacetime rescue in the history of mainland Britain. Source
  • Miraculously, there were no fatalities, with only 1 reported casualty - a broken thumb. Source
  • Residents moved into temporary accommodation while their flooded homes
    were dried out and repaired. Source
 
Economic Consequences
  • 58 properties were flooded, 4 of which were demolished, The Visitor Centre, Clovelly Clothing,Things and the Harbour Light. Source
  • A further 40 properties were flooded in Canworthy Water, Bude, Helebridge and
    Crackington Haven with severe flooding at Otterham,Week St Mary, Marshgate,
    Millook and Camelford. Source
  • 84 wrecked cars were recovered from Boscastle’s harbour and streets, 32 could still be out at sea. Source
  • The significant infrastructure damage to buildings and services, could cost North Cornwall District Council up to £2 million. Source
  • The number of day visitors is running near to usual levels, although fewer people are staying overnight. Source
  • There was also serious damage to Boscastle’s infrastructure, with water, power and telephone services cut and roads extensively damaged. Source
 
Environmental Consequences
  • Raw sewage contaminated floodwater at Boscastle and led to public health concerns after about 300m of sewer pipes were blocked or washed away. Source
 
Redevelopment
  • The village’s infrastructure was restored: water supplies, sewers and telephone lines which were put out of action were repaired, the electricity sub-station replaced and damaged roads reinstated. Source
  • Business owners set a deadline of Easter – the start of the tourist season – for reopening, but some were back in business much earlier, including Boscastle Pottery and the Cornish Stores mini-market. Source
  • Some 1,850 tonnes (150 truck-loads) of debris were shifted by our emergency
    workforce at Boscastle. Source
 

Vidoes

 
 
Metrorological Phenomena
Topography
Rescue Efforts
Social Consequences
Economic Consequences
Environemntal Consequences
Redevelopment
Images
Videos
 
Boscastle - The Flood
Boscastle - The Flood - North Cornwall District Council
Living with the Risk
Environmental Agency - Living with the Risk.
Flooding in Boscastle and North Cornwall
HR Wallingford - Flooding in Boscastle and North Cornwall, August 2004 - Studies Report.
 

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