DefinePK

Abstract

Post-glacial geomorphological settings bearing vast amounts of colluvium as well as alluvial and moraine deposits are typical features in high mountainous environments such as the Himalayas, the Hindu Kush, the Pamir, the Karakoram and the Tien Shan. Due to a lack of alternative living space in narrow valleys, agglomerations are often located on these unstable grounds and regularly experience displacements across the ground surface and subsequent damage to building stock and infrastructure.
Hosting two post-glacial landslide deposits and one gravitational creep within its inhabited areas, the village of Tusion, South-Western Tajikistan, was chosen to conduct geophysical surveys with the aim to determine the geomorphological causes of regularly experienced slope deformations with a particular interest in the contribution of non-isolated irrigation channels crossing the mountain flanks. Over the last two decades, uncontrolled seepage from a network of small-scale irrigation channels is believed to be responsible for water infiltration to deeper horizons and–thereby–reactivate ancient sliding surfaces within the two landslide deposit zones. Also, the gravitational creep in one village part seems to be likewise triggered.
Using refraction seismics and Schlumberger geoelectrics, stratigraphic structures, properties of involved rock material and saturation patterns were assessed in order to provide complementary information about the underground of concerned slopes to a previously conducted hazard assessment by separate Non-Governmental Organizations. Results of the geophysical surveys show conclusive correlations with the hazard maps and local damage reports straining that one of the major destabilizing factors for all concerned slopes consists of uncontrolled water dissipation to the underground.