Damming predisposition of river networks: A mapping methodology

Landslide dams may collapse within few hours/days after their formation resulting in destructive flooding wave. Due to the limited time available since their formation, forecasting tools able to assess the damming susceptibility over large areas are more advisable for prevention and setting up mitigation measures. A semi-automated GIS-based methodology is proposed in this work to map the spatial damming predisposition over large areas, to analyse consequence and risk scenarios. The procedure is based on a morphological index that use a statistical correlation between morphometric parameters to spatially assess the chance of a river obstruction through the reactivation of an existing landslide. This damming mechanism were tested on the Arno River basin (9116 km2) in Italy, where about 30,000 landslides are mapped. The highest mountain ridges in the Eastern part of the area resulted as the most susceptible to damming in the basin. The concentration of the historical landslide dams endorses the results for this basin.