Geometric approach based tool for shallow landslides propagation assessment (ShaLPA) at basin scale

Hazard maps for shallow landslides at the basin or regional scale often provide information solely about past events and/or potential source areas. Despite the availability of several propagation assessment software tools, runout maps for potential shallow landslides at the basin scale remain scarce. To address this gap, the ShaLPA runout GIS tool was developed as an easy-to-use and efficient solution. Based on a geometric approach, the tool consists of five distinct, sequential scripts that begin with defined source areas. By processing a detailed Digital Terrain Model, the first script identifies the starting points and the second traces the potential paths of shallow landslides. The third script calculates the runout, while the fourth estimates velocity distribution and kinetic energy along the paths. The fifth script assess the reliability of the model results using two different indicators. ShaLPA was first tested in the Giampilieri and Briga area (Sicily, Italy), providing encouraging results. The simplicity of the ShaLPA tool promotes the integration of runout and failure susceptibility analyses, enhancing the comprehensiveness of hazard and risk assessment and improving the effectiveness of landslide mitigation measures.