Debris-flow risk assessment and land management at municipal scale

Abstract

Natural-risk levels assessment related to debris-flow and flood occurrence is a crucial process for the development of proper land management policies in densely urbanized alluvial-fans of the Alpine region. Mitigation measures are built to protect edified areas lowering natural-risk level below defined thresholds and to allow socio-economic development at local scale, especially in mountainous areas, where urban expansion is strongly conditioned by local morphology and natural processes dynamics. In 2009, SEA Consulting was instructed by Bruzolo Municipality (Susa Valley, Piedmont Region, NW Italy) to assess the efficacy of a levee along the Pissaglio riverbanks designed to protect a densely populated area. The study was conducted considering debris-flow hazard by following two different approaches: monodimensional ("Colate detritiche", that implements Voellmy and Takahashi equations) and bidimensional (RASH3D code, assuming a Voellmy rheology) models. Flood hazard was assessed by means of the program HEC-RAS. The results of the study are presented in this paper. © Springer-Verlag Berlin Heidelberg 2013.