Landslides in the Yankalilla district of South Australia

Abstract

The anthropogenic factor is a recent addition to the science of geomorphology, although, as early as 1864 G.P. Marsh warned of the deleterious erosional consequences of the overclearing of vegetation. The Fleurieu Peninsula, eighty kilometres south of Adelaide, South Australia, affords the opportunity to study in detail the results of man's activity upon the landscape, wrought by settlement in the second half of the last century. Cleared initially for the growing of wheat, the area now shows the consequences of erosion. in the form of deep gullies and mass-movements. Gullying results from the concentration of run-off in the vertical furrows employed before the introduction of contour ploughing. Landsliding is considered the most significant process of mass-movement operating in the area and while there has not been a disaster in the sense of loss of life such as occurred in Hong Kong (So,1971 ) or Yungay , Peru, where twenty five thousand are known to have perished (Cooke &Townshend,1970), landsliding represents a serious economic loss of productive land. With gullying, it is estimated by Campana (1954) that landsliding causes a twenty percent reduction of arable land. These landslides pose a number of problems, first in relation to distribution, morphology and active and passive causes as suggested by Sharpe (1938) and second to the time lapse between the initial clearing and subsequent movement of the land. These problems are investigated in this study.