Local-Scale Risk Analysis and Mitigation of Debris Flow Endangering a Densely Populated Urban Area - a Case Study from Tyrol, AT.

Innsbruck

2014

6 S.

Monographie

11227S

180494

Debris flows present a serious threat to Alpine settlements and infrastructure. A case in point is the city Innsbruck (Tyrol, Austria). In case of extremely heavy precipitation in the Höttingerbach catchment, located in the city s north-west, flooding and debris flow may endanger Innsbruck s district Hötting. The calcula-tion of the debris flow risk and the discussion of the type and impact of a potential risk mitigation measure, are presented in the following. The risk analysis consisted of the following steps: a) determining debris flow hazard potential; b) estimating damage potential of material assets and persons; c) combining a) and b) to calcu-late the societal risk. The results of the risk analysis revealed Hötting s high sus-ceptibility towards debris flow and flooding, with 542 houses and over 4100 per-sons potentially exposed. Therefore, a risk mitigation measure was elaborated, consisting of a water retention basin near the apex of the alluvial fan. An analysis of the potential impact of this measure on the risk situation showed a distinct re-duction of the potential damage to material assets and persons as well as a positive cost-benefit ratio.Risk management, Debris flow, Retention basin, Hydraulic engineer-ing, Höttingerbach Tyrol