Discussion on ‘Towards the prediction of subsidence risk upon the chalk outcrop’ by C. N. Edmonds

Abstract

E. J. Wilson write: Figure 1 of Edmonds' paper suggests a geographical distribution of solution features which is highly distinctive yet apparently defies geological or climatological explanation. One is reluctant to accept such distribution as a starting point for the analysis of a problem, unless either it can be explained, or it can be shown that it is not due to any other spurious factor. It is immediately obvious that the lowest density of solution features recorded is for Salisbury Plain, a large proportion of which, as a military training ground, has a land use which would be expected to have a very low sensitivity to solution features. It is also obvious that most areas of high density lie within the Home Counties. This suggests the hypothesis that solution features are more likely to be discovered, and hence to become the subject of available data, in more highly-developed areas. To put this hypothesis to the test, a comparison was made between population density as shown in the Ordnance Survey Atlas of Great Britain , and the density of solution features as shown by Edmonds. A direct and reliable comparison would be difficult, however, without much more detailed analysis, since there is considerable overlap between areas from the two sources. Furthermore, there are many small areas of high population density, but these are mostly concentrated in valley bottoms, which Edmonds' Fig. 2 shows are not a preferred location for solution features; therefore they have been ignored on the basis that they would