Page 232 - Fundamentals of Geomorphology

KARST LANDSCAPES 215

Plate 8.18 Helictites in Ogof Draenen, Pwll Ddu, South Wales.
(Photograph by Clive Westlake)

HUMAN IMPACTS ON KARST swiftly finds its way underground, where it blocks pas-
sages, diverts or impounds cave streams, and chokes cave
Surface and subsurface karst are vulnerable to human life.
activities. Caves are damaged by visitors, and agricultural The prevention of soil erosion and the maintenance
practices may lead to the erosion of soil cover from karst of critical soil properties depend crucially upon the
areas. presence of a stable vegetation cover. The Universal Soil
Loss Equation or its more recent derivatives (p. 179)
can predict soil erosion on karst terrain, but higher
rates may be expected on karst as compared with most
Soil erosion on karst
other soil types because features of the geomorphology
Karst areas worldwide tend to be susceptible to soil conspire to promote even greater erosion than else-
erosion. Their soils are usually shallow and stony, and, where. In most non-karst areas, soil erosion depends
being freely drained, leached of nutrients. When vegeta- upon slope gradient and slope length, as well as the
tion is removed from limestone soils or when they are other factors in the USLE. It also depends partly on
heavily used, soil stripping down to bedrock is com- slope gradient and slope length in karst terrain but,
mon. It can be seen on the Burren, Ireland, in the in addition, the close connections between the surface
classic karst of the Dinaric Alps, in karst of China, drainage system and the underground conduit system
in the cone karst of the Philippines, and elsewhere. produce a locally steeper hydraulic gradient that pro-
In Greece, soil stripping over limestone began some motes erosive processes. Moreover, eroded material in
2,000 years ago.The limestone pavement above Malham karst areas has a greater potential to be lost down joints
Cove (Colour Plate 4) may be a legacy of agricultural and fissures by sinkhole collapse, gullying, or soil strip-
practices since Neolithic times, soils being thin largely ping. An adequate vegetation cover and soil structure
because of overgrazing by sheep. Apart from resulting (which reduce erodibility) take on a greater significance
in the loss of an agricultural resource, soil stripping has in lessening this effect in karst areas than in most other
repercussions in subterranean karst. The eroded material places.