Case Study: Lynmouth
Lynmouth is a small town in Devon, England, on the north border of Exmoor. The small town is on the meeting point of the West Lyn and East Lyn rivers, in a gorge 700 pess ( 210 m ) below Lynton, to which it is connected by the Lynton and Lynmouth Cliff Railway. The two small towns are governed at local degree by Lynton and Lynmouth Town Council. Lynmouth is rural country with non much corporate activity traveling on. It is in the coastal portion of the United Kingdom Island, which makes it a big tourer attractive force topographic point. Peoples normally come to Lynmouth for Tourism and the activities they do are chiefly ahorse siting, fishing and boat drives.
Flood in 1952
On the 15th and 16th of August 1952, a storm of tropical started over in south-west England, precipitating 229 millimeters ( 9.0 in ) of rain within 24 hours on a coastal country, Exmoor. It is thought that a cold forepart started a electrical storm, and the storm worsened. An immediate surface run-off occurred and it caused a brassy inundation. Large sums of floodwaters moved down the northern portion, meeting upon the small town of Lynmouth ; in peculiar, in the upper West Lyn valley, a dike was formed by fallen trees. This caused possible energy to organize and after a while the H2O broke through the dike directing a immense moving ridge of H2O and fragments down that river. Overnight, over 100 edifices were destroyed or earnestly damaged along with 28 of the 31 Bridgess, and 38 autos were washed out to sea. In entire, 34 people died, with a farther 420 made homeless. Overall the rainstorm lasted about 14 hours and 300 million gallons of rain precipitated.
Cause of the Flood
The little but steep sided drainage basin in which Lynmouth was situated increased the hazard of deluging in the country. The steep sides encouraged greater surface overflow and combined with the little drainage basin size meant any H2O could make the river reasonably rapidly. This was made worse by the high drainage denseness of the country due to the impermeable stones of the country around Exmoor which formed the beginning of the river ; once more increasing the sum of surface overflow following rainfall. Prior to August 15th 1952 Lynmouth had received above norm rainfall for 12 out of the first 14 yearss of the month intending the dirts were already saturated and the river degrees high. On August 15th a heavy electrical storm resulted in 200mm falling in 14 hours, one of the three heaviest rainfalls recorded in the UK. This heavy rain combined with the saturated land and rapid surface overflow resulted in a immense volume of H2O fluxing down the river. As Lynmouth is situated at the meeting of the East and West Lyn rivers the volume of H2O was increased farther at this point and the was far beyond the capacity of the river channel doing the river to split its Bankss. This resulted in lay waste toing inundations as the West Lyn which had been diverted during the building of parts of Lynmouth recapture its natural class, fluxing straight through the small town.
Following the Lynmouth inundation catastrophe, inundation direction programs were put in topographic point to seek and guarantee such a catastrophe could non go on once more by pull offing any extra rain H2O so that the River could manage it in the in the hereafter.
A figure of flood direction schemes were put in topographic point:
& A ; bull ; The oral cavity of the East Lyn was widened to increase capacity and let H2O to rapidly go through into the Bristol Channel
& A ; bull ; The West Lyn was straightened to increase channel efficiency – unbending the channel reduces clash and increases speed, enabling H2O to go through the channel every bit rapidly as possible doing it more efficient in get bying with inundation Waterss ;
& A ; bull ; The West Lyn was non redirected, alternatively being allowed to follow its natural class
& A ; bull ; Floodplain zoning was used to place countries around the river most at hazard from deluging. Building limitations were so put in topographic point with countries near to the river which are most prone to deluging being left as unfastened infinites such as auto Parkss.
& A ; bull ; Bridges were made wider and taller to let inundation H2O to tr avel rapidly beneath them and to cut down the likeliness of dust going trapped and moving like a dike as had happened in 1952 ;
& A ; bull ; Embankments were built by the river to increase channel capacity and cut down the likeliness of implosion therapy ;
& A ; bull ; More trees were planted upriver in the beginning country to seek and cut down initial surface overflow through interception and the soaking up of H2O. Tree roots besides help to better infiltration by opening up the dirt and decelerating down the rate at which H2O reaches the land ;