Traveller's tales

Sunday, August 27, 2006

The forces of Nature: Lynmouth, 1952

The power of water in a river obeys logarithmic laws, not arithmetical ones; if the volume doubles, the power of the torrent increases by a factor of eight – the ‘cube law’. Ask anyone who was in Boscastle, Cornwall, on a dreadful day in 2003, or in the picturesque village of Lynmouth, North Devon, in 1952.

Ask anybody from a desert nation like the United Arab Emirates, or one with large deserts – rock or sand within its borders, like the Sultanate of Oman; ask them about the power of the flood in a wadi. Many has been the time when an unsuspecting ex Pat has all but lost his beloved 4 by 4 in the deluge that surrounds him and almost swarms over his Land Cruiser or his Range Rover. People have lost their lives in such flooded watercourses - wadis. Water on the move is hugely powerful.

Fortunately for most countries, soil and vegetation inhibits what is termed ‘run-off’, so that a heavy downpour of rain does not translate itself into an immediate rise in the water level of a river. Vegetation and soil, and sometimes permeable rock such as limestone, delays this rise, only allowing water to rise in a river bed once that water has percolated through layers of obstacles, be they organic or otherwise.

Typically in arid areas with little or no plant cover or soil of any kind, rivers react virtually at once to heavy rainfall. The resulting flooding of dried water courses – wadis – is immediate, powerful and potentially devastating to anything or anybody crossing that water course.

Several lives were lost in Oman’s aptly named “Snake Gorge’, known locally as Wadi Bani Awf, near the town of Rustaq. Heavy rainfall upstream produced a flash flood that was only detected when it was too late.

In Lynmouth, only a short distance downriver from Lynton, the effects of a sudden increase in the volume of water, both falling from the sky and filling the river, was devastating. Boulders the size of houses were dislodged and wreaked havoc on dwellings further down. The power of water, combined with the weight of rock forced downstream was sufficient to cause widespread destruction of buildings.
Robert Leslie Fielding

Visit My Website