MASS MOVEMENT IN NORTHEAST AFGHANISTAN

Mass movements of nearly all types occur in Afghanistan but in the rocky and rugged, high-relief Hindu Kush and eastern Pamir mountains of Badakshan Province in northeastern Afghanistan, rockslides and rock falls are commonly intermixed into 20 large sized slope-failure complexes with many other types and times of movement. Many smaller rock falls and rockslides occur that were not included in this study. Where higher altitudes prevail in the region, ice-cemented and ice-cored rock glaciers commonly overlie or are intermixed into the landslides. At lower altitudes in western Badakshan, covering mantles of Quaternary loess, which were deflated from the Karakumsky Desert of Turkmenistan and steppes and deserts of northern Afghanistan, thicken from close to their western sources and thin into eastern mountain repositories. Some 24 loess slides and flows were mapped and measured. Inasmuch as seismic energy sources are maximal in southern Badakshan, and relief, slope angles, low temperature and precipitation all increase from west to east as well; causes of the pervasive mass movements are plentiful. Some weak sedimentary lithologies of late Tertiary age that were downfaulted into crystalline rocks or draped across them also contribute to instability.

Using high resolution satellite imagery and digital elevation models, we delineated all large landslides. Landslide morphometric characteristics were then assessed using global parameters, parameter-area and parameter-altitude functions. We then segmented each landslide into terrain units based upon geomorphometric characteristics in order to characterize the spatial-organization structure related to zones of erosion and deposition. Geomorphometric and object-oriented analyses indicate that many of the massive slope failures can be uniquely characterized and differentiated into various types that are reflective of their potential impacts upon the landscape. Results suggest that mass movements can exhibit unique topographic signatures that can be used to better assess hazards in many areas. Development of roads, bridges, buildings, and irrigation networks should be done with care in these regions.