SIR - I would like to make a few comments on the discussion about the erosion of the cliffs at Sidmouth
I was born in Lowestoft, the most eastern point of England, where much of the coast is subject to erosion. I studied geography for Higher School Certificate, where erosion was part of the course. Our county surveyor was SW Mobbs, who published research papers on projects he had dealt with for various authorities. He was asked to prepare a scheme for protecting the town and the Rural District and suggested groynes, in front of a sea wall extending to the town boundary to help build up deposits of sand for protection. He proposed a scheme on either end of the wall, of groynes of various types which would slow down the north and south movements of the sea and raise the level of beach to protect the cliffs, beaches and dunes.
When the council was confronted by the estimated cost of the project they said they could not afford the whole scheme, just adopting the scheme in the area in front of the town. This left the coast to the north and south of the town to be paid for by the Rural District Council, who said they could not afford it. Mr Mobbs warned that while the smaller development would initially protect the town, the north and south flanks of the wall would be dangerously exposed by high tides, sea surges and storms. This happened in the North Sea Surge of 1953 when the sea scoured the land behind the wall and flooded the town.
In Sidmouth, the rock deposits are helping to build up the beach with sand which would have protected the cliffs and Alma Bridge. I have tried to get details of Mobb’s research papers which we studied, to no avail. Various formulae he developed showed the height of the waves depended on the depth of the water; the waves breaking against the cliffs depended on the height of the water at its base and the wavelength between the waves. He showed that solid structures remove most of the material which the tides erode along the coast, but various groyne-like structures slow down the coastal movement and allow a more equitable distribution of the protective material.
We also studied the Tennessee Valley Authority which was set up in 1933 to deal with the problems created by bad practices in the agricultural industry: the removal of hedges to make bigger fields for the large machines which were being used; filling in of ditches, ponds and reservoirs to cause a faster run-off of the rain water; ploughing against the contours and the use of chemical fertilisers without adding the compost which would help to give a structure to the soil. This allowed monoculture of one crop which left the soil open to the wind and rain when the soil was bare, and floods where roads and housing development added to the problem.
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