The contribution of human activity to landslide was also being questioned
(Ramsay, 1985, 1986). Also some studies, such as that of Fleming (1983), were
indicating that soil erosion on cultivated slopes was not as high as was thought.
Above all, it was recognized that reliable and accurate data with which to test the
various components of the ‘Theory’, both at the hillslope and catchment scales, were
largely unavailable (Ives & Messerli, 1989).