|Date||15 and 16 August 1952, one night.|
|Location||Lynmouth, Simonsbath, Filleigh, Middleham (never rebuilt), Devon|
On 15 and 16 August 1952, a storm of tropical intensity broke over south-west England, depositing 229 millimetres (9.0 in) of rain within 24 hours on the already saturated soil of Exmoor, Devon. It is thought that a cold front scooped up a thunderstorm, and the orographic effect worsened the storm. Debris-laden floodwaters cascaded down the northern escarpment of the moor, converging upon the village of Lynmouth; in particular, in the upper West Lyn valley, a dam was formed by fallen trees etc., which in due course gave way, sending a huge wave of water and debris down the river. A guest at the Lyndale Hotel described the night to the Sunday Express:
From seven o'clock last night the waters rose rapidly and at nine o'clock it was just like an avalanche coming through our hotel, bringing down boulders from the hills and breaking down walls, doors and windows. Within half an hour the guests had evacuated the ground floor. In another ten minutes the second floor was covered, and then we made for the top floor where we spent the night.
The River Lyn through the town had been culverted to gain land for business premises; this culvert soon choked with flood debris, and the river flowed through the town. Much of the debris was boulders and trees.
Overnight, more than 100 buildings were destroyed or seriously damaged along with 28 of the 31 bridges, and 38 cars were washed out to sea. In total, 34 people died, with a further 420 made homeless. The seawall and lighthouse survived the main flood, but were seriously undermined. The lighthouse collapsed into the river the next day.
The root cause of the flood was heavy rainfall associated with a low-pressure area that had formed over the Atlantic Ocean some days earlier. As the low passed the British Isles, it manifested as a weather front which caused exceptionally heavy rainfall, the effect of which was intensified because the rain fell on already waterlogged land; the effect was further exacerbated over Exmoor by an orographic effect. The lack of satellite data in 1952 meant the weather could not be forecast as reliably as it can be today.
Similar floods had been recorded at Lynmouth in 1607 and 1796. After the 1952 disaster, Lynmouth village was rebuilt, including diverting the river around the village. The small group of houses on the bank of the East Lyn river called Middleham between Lynmouth and Watersmeet was destroyed and never rebuilt. Today, there stands a memorial garden.
On 16 August 2004, a similar event happened in Cornwall, when flash floods caused extensive damage to Boscastle, but without loss of life. The hydrological setting of these two villages is very similar.
The theory was fuelled by a 2001 BBC Radio 4 documentary, suggesting that the events of 1952 were connected to Project Cumulus. The programme alleged that "the infamous Lynmouth flood disaster came only days after RAF rain-making experiments over southern England", and that secret experiments were causing heavy rainfall. According to the programme, "classified documents on the trials that Project Cumulus contributed to the conditions that caused this flood have gone missing." A few days before the disaster a seeding experiment was carried out over southern England. Alan Yates, an aeronautical engineer and glider pilot who was working with the operation, sprayed salt in the air and was "elated" to learn of a heavy rainfall in Staines shortly after.
Experts have said the experiments could not have caused the accident. Meteorologist Philip Eden provides several reasons why "it is preposterous to blame the Lynmouth flood on such experiments". Eden notes that "there has never been unequivocal evidence of how successful these rain-making programmes have been" but that the technology was not secret. According to Eden, "rain-making experiments were talked about all over the place in the early-1950s and that The Royal Meteorological Society's popular magazine, Weather, devoted a whole issue to the subject in July 1952 – just a month before the Lynmouth disaster." Eden explains, that Frank Ludlam of Imperial College, described in detail the physical processes underpinning cloud-seeding research in the UK" but that "scientists involved in rainfall stimulation were only interested in seeding individual cumulus clouds" rather than large-scale experiments. Last, according to Eden, the rain clouds over the Southern U.K. in August 1952 were part of a large depression that was several hundred miles across. "Heavy rain fell over the whole of the West Country and South Wales, and it was caused by a depression which had stagnated in the Southwest Approaches for two days." Eden says, "Similar depressions have triggered serious flooding in southwest England at regular intervals, and previous devastating floods hit Lynmouth in the 18th and 19th centuries" and "prolonged heavy rain associated with it was caused by the large-scale lifting of very moist air." He does not believe cloud-seeding would have had much of an impact on the amount of rain released by the depression.
The conspiracy theory prompted local novelist Pamela Vass to write a mystery novel titled Seeds of Doubt based on the events. Vass commented "I'm a sucker for a mystery, and I think we all do get really absorbed by conspiracy theories and the idea that information is being withheld from us."
- Lynmouth Flood 1952
- Filleigh Village hall Memorial
- Mcginnigle, JB (2002). "The 1952 Lynmouth floods revisited". Weather. 57 (7): 235–242. doi:10.1256/004316502760195894. (subscription required)
- "Middleham Gardens". Visit Lynton and Lynmouth. Retrieved 7 July 2016.
- "Where is the next Boscastle?". BBC News. 7 October 2004. Retrieved 2008-06-14.
- Hilary Bradt; Janice Booth (11 May 2010). Slow Devon and Exmoor. Bradt Travel Guides. p. 249. ISBN 978-1-84162-322-1.
- "Weather Weapons to Attack Mankind". Greatest Conspiracy Theories (4/10). British Pathé. 21 August 1952. Retrieved 14 August 2016.
- Rain-making link to killer floods, BBC, 2001-08-30, retrieved 2007-07-21
- Vidal, John and Helen Weinstein, RAF rainmakers 'caused 1952 flood', The Guardian, 2001-08-30, retrieved 2007-07-21.
- The day they made it rain, Philip Eden, WeatherOnline
- "Flood 'mystery' inspires novelist". North Devon Journal. 12 January 2012. Retrieved 14 August 2016.
- Delderfield, E. R. (1953) The Lynmouth flood disaster. J. Atkins and J. Letheren, Exton.