title: Debris-flow risk analysis in a managed torrent based on a stochastic life-cycle performance.
abstract: Two key factors can affect the functional ability of protection structures in mountains torrents, namely (i) infrastructure maintenance of existing infrastructures (as a majority of existing works is in the second half of their life cycle), and (ii) changes in debris-flow activity as a result of ongoing and expected future climatic changes. Here, we explore the applicability of a stochastic life-cycle performance to assess debris-flow risk in the heavily managed Wartschenbach torrent (Lienz region, Austria) and to quantify associated, expected economic losses. We do so by considering maintenance costs to restore infrastructure in the aftermath of debris-flow events as well as by assessing the probability of check dam failure (e.g., as a result of overload). Our analysis comprises two different management strategies as well as three scenarios defining future changes in debris-flow activity resulting from climatic changes. At the study site, an average debris-flow frequency of 21 events per decade was observed for the period 1950-2000; activity at the site is projected to change by +38% to -33%, according to the climate scenario used. Comparison of the different management alternatives suggests that the current mitigation strategy will allow to reduce expected damage to infrastructure and population almost fully (89%). However, to guarantee a comparable level of safety, maintenance costs is expected to increase by 57-63%, with an increase of maintenance costs by ca. 50% for each intervention. Our analysis therefore also highlights the importance of taking maintenance costs into account for risk assessments realized in managed torrent systems, as they result both from progressive and event-related deteriorations. We conclude that the stochastic life-cycle performance adopted in this study represents indeed an integrated approach to assess the long-term effects and costs of prevention structures in managed torrents.
authors.affiliation: Dendrolab.ch. Institute for Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland; Climate Change an Climate Impacts (C3i) Institute for Environmental Sciences, University of Geneva, 66 Boulevard Carl-Vogt, CH-1205 Geneva, Switzerland. Electronic address: juan.ballesteros@dendrolab.ch.
authors.forename: J A
authors.initials: JA
authors.lastname: Ballesteros Cánovas
authors.affiliation: Dendrolab.ch. Institute for Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland; Climate Change an Climate Impacts (C3i) Institute for Environmental Sciences, University of Geneva, 66 Boulevard Carl-Vogt, CH-1205 Geneva, Switzerland; Department of Earth Sciences, University of Geneva, 13 rue des Maraîchers, CH-1205 Geneva, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Stoffel
authors.affiliation: Centre National de la Recherche Scientifique (CNRS) UMR6042 Geolab, 4 rue Ledru, F-63057 Clermont-Ferrand Cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Corona
authors.affiliation: Institute for Alpine Hazards, University of Natural Resources and Life Sciences, Vienna (BOKU), A-1190 Vienna, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Schraml
authors.affiliation: University of Graz, Wegener Center for Climate and Global Change (WegCenter), A-8010 Graz, Austria; Central Office for Meteorology and Geodynamics (ZAMG), A-1190 Vienna, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Gobiet
authors.affiliation: University of Graz, Wegener Center for Climate and Global Change (WegCenter), A-8010 Graz, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Tani
authors.affiliation: Austrian Institute of Economic Research, A-1030 Vienna, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Sinabell
authors.affiliation: Institute for Alpine Hazards, University of Natural Resources and Life Sciences, Vienna (BOKU), A-1190 Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Fuchs
authors.affiliation: Institute for Alpine Hazards, University of Natural Resources and Life Sciences, Vienna (BOKU), A-1190 Vienna, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Kaitna
keywords: Check dams; Debris flow; Deterioration; Life-cycle performance; Natural hazard; Risk assessment; Wartschenbach