Landslide-Dammed Mapping and Logistic Regression Modeling Using GIS and R Statistical Software in the Northeast Afghanistan

A complex terrain and topography resulted in an enormous landslide-dammed area northeast of Afghanistan. Moreover, debris, rock avalanches, and landslides occurrences are the primary source of lakes created within the area. Recently, instances have increased because of the high displacement and mass movement by glacial and seismic activities. In this study, using GIS and R statistical software, we performed a logistic regression modeling in order to map and predict the probability of landslides-dammed occurrences. Totally, 361 lakes were mapped using Google Earth historical imagery. This total was divided into 253 （70%） lakes for modeling and 801 （30%） lakes for the model validation. They were randomly selected by creating a fishnet for the study area using Arc toolbox in GIS. Four independent variables that are mostly contributed to landslide-dammed occurrences consisting of slope angles, relief classes, distances to major water sources and earthquake epicenters, were extracted from DEM （digital elevation model） data using 85-meter resolution. The result is a grid map that classified the area into Low （16,834.98 km2）, Medium （2,217.302 kin：） and High （2,013.55 km2） vulnerability to landslide-dammed occurrences. Overall, the model result has been validated by using a ROC （receiver operator characteristic） curve available in SPSS software. The model validation showed a 95.1 percent prediction accuracy that is considered satisfactory.

Dated deposition couplets link catchment erosion flux with storm discharge on the Chinese Loess Plateau

Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) serves as a valuable archive of past erosion history. Deposition couplets and annual freeze–thaw layers were firstly identified for the sedimentary succession of the Jingbian reservoir on the northern CLP with high-resolution XRF core scanning. The deposition couplets in the reservoir since 1963 A.D. were further dated with ^(137) Cs activity. We found consistent one-to-one correspondence between couplet specific sediment yield and storm intensity. The reconstructed soil erosion history highlights the control of storm intensity and frequency on loess erosion on the northern CLP in the past hundreds of years.

Modeling potential scenarios of the Tangjiashan Lake outburst and risk assessment in the downstream valley

This research is devoted to Taniashan Lake, a quake landslide-dammed lake, situated in Sichuan Pro- vince, China, which was formed by a landslide triggered by the Wenchuan Earthquake on 12 May 2008. A STREAM_2D two-dimensional hydrodynamic model of Russia was applied to simulate the process of two flood scenarios： 1, lake dam outbreak, and 2, dam overtopping. An artificial dam outbreak was made after the earthquake to lower the water level of the lake in 2008, which led to a great flood with a maximum water discharge of more than 6400 m3/s. The negative impact of the flood was reduced by a timely evacuation of the population. Flood hazards still remain in the event of new landslides into the lake and lake dam overtopping （Scenario 2）, in which case a maximum water discharge at the dam crest would reach 5000 m3/s, placing the population of Shabacun and Shilingzi villages in the zone of flood impact.