Debris-flow risk analysis in a managed torrent based on a stochastic life-cycle performance

Area of Science:

• Hydrology and Natural Hazards
• Civil Engineering
• Climate Change Adaptation

Background:

• Protection structures in mountain torrents face challenges from aging infrastructure and changing debris-flow activity due to climate change.
• Existing infrastructure requires significant maintenance, with many structures nearing the end of their service life.
• Climate change is projected to alter debris-flow frequency and intensity, impacting the effectiveness of current protection measures.

Purpose of the Study:

• To assess the applicability of stochastic life-cycle performance analysis for evaluating debris-flow risk in managed torrent systems.
• To quantify expected economic losses associated with debris-flow events, including infrastructure maintenance and potential failures.
• To compare different management strategies under various climate change scenarios for debris-flow activity.

Main Methods:

• Utilized a stochastic life-cycle performance model to assess debris-flow risk at the Wartschenbach torrent in Austria.
• Incorporated maintenance costs for infrastructure restoration and assessed the probability of check dam failure.
• Analyzed two management strategies and three climate-driven debris-flow activity scenarios.

Main Results:

• The study site experienced an average debris-flow frequency of 21 events per decade (1950-2000).
• Projected changes in debris-flow activity range from +38% to -33% based on climate scenarios.
• The current mitigation strategy effectively reduces expected damage (89%), but maintenance costs are projected to increase by 57-63% to maintain safety levels.

Conclusions:

• Stochastic life-cycle performance analysis provides an integrated approach for assessing long-term effects and costs of torrent prevention structures.
• Maintenance costs are a critical factor in risk assessments for managed torrent systems, influenced by both gradual deterioration and event-related damage.
• Adapting management strategies and accounting for increased maintenance costs are essential for ensuring the long-term safety and functionality of mountain torrent protection infrastructure under changing climatic conditions.