MASS MOVEMENT IN NORTHEASTERN AFGHANISTAN

Mass movement of nearly all types occurs in Afghanistan but in the high-relief Pamir and Hindu Kush mountains of northeastern Afghanistan, only rock falls, rock slides and massive slope-failure complexes were mapped. Velocities of movement ranged from high speed to imperceptible. Where higher altitudes prevail, extensive overlying ice-cemented and ice-cored rock glaciers occur, indicating considerable antiquity in some cases. Dominant rock types involved are fault-shattered crystalline gneisses and granites, but some weak sedimentary lithologies downfaulted into crystalline rocks, or draped across them, have also contributed slow debrisflow/earthflow failure types. Inasmuch as high-energy seismic sources are maximal in southern Badakhshan, and relief, slope angles and precipitation all increase into the mountains, the causes of the pervasive mass movement are plentiful. Some diamictons previously mapped as moraine or alluvium are actually large slope failures. Aspect plots of 20 slope failures show dominance of southeast and southwest movement directions, which are largely related to collapse of previously glaciated fault scarps. Sizes of some failures are large, with masses as much as 10-12 km³ in places, including the Lake Shewa landslide dam, which at 2.3 km³ is the second largest mass-movement valley obstruction in the world. High resolution satellite imagery and digital elevation models were used to characterize spatial-organization structures of slope failures. Results suggest that mass movements in Afghanistan exhibit unique and diagnostic topographic signatures that can be used to define their location, assess movement type, and allow analysis of hazard, especially where landslide-dam breakout floods threaten. Development of roads, bridges, buildings, and irrigation networks should be done with care in these regions.