Geomorphological, hydrological and sedimentary control of an artificially induced debris flow

Artificial infiltration of additional water induces a debris flow of 65 m(3) in the tills of the Lainbach catchment, Northern Limestone Alps, Under natural conditions pore-water pressures and moisture conditions are close to failure, The supply of water primarily causes a rise in sediment water contents and a loss of cohesion in the clay-rich glacial deposits. The till material is dropped onto a funnel shaped slope by an active rotational landslide, which has been active for about 50 years. Forming shallow, slow-moving debris slides, the material is transported downslope, across a pre-existing shear plane of glaciolimnic clays. The geometry of the clay surface controls the sediment outburst and movement tracks. The positions of the glaciolimnic clays were identified by geophysical soundings. For debris flow initiation a water content of about 21% by weight and pore-water pressures of up to 15 kPa were measured. (C) 2000 Elsevier Science Ltd. All rights reserved.