Geoscience Reference
In-Depth Information
in the Peak District, or the Three Peaks area in the Yorkshire Dales, where excessive
trampling has worn away the vegetation cover and exposed the soil to gully erosion
by heavy rain. It was a surprise, therefore, to many people when the Soil Survey pub-
lished its warning that agricultural land in Britain was suffering serious erosion, and
set up a 5-year programme in 1982 to monitor it. A series of air photographs in fif-
teen areas was used to identify rills and soil outwash at the bottom of slopes. Field
surveyors then visited sample sites to check the photographic interpretations, and to
measure the amounts of soil deposited.
Water erosion of farm land in this country is not new, for Whyte mentions bald
areas in fields, piles of eroded soil on roadways, and the value of hedges and contour
trenches in arresting soil movement in hilly districts. However, it has become signi-
ficantly worse in the last twenty years as a result of farming innovations: first, the
ploughing up of old grassland, especially the chalk downland slopes and previously
uncultivated parts of Brecon, Radnor and Exmoor; secondly, the increase in field size
due to removal of hedges, which had often been placed at critical changes in slope,
and had served to check the downhill drift of soil; and thirdly, the introduction of con-
tinuous arable cropping, and the use of tramlines which, because of their compaction,
inhibit infiltration and start run-off.
F
IG. 64
Deposition of soil from water erosion in Cambridgeshire. (Photograph by R. Evans.)
Water erosion is a fairly local problem at present, affecting mainly light and
coarse textured soils on valley sides, but about one fifth of cultivated land in lowland
