Brief communication: Stay local or go global? on the construction of plausible counterfactual scenarios to assess flash flood hazards

Abstract

Spatial counterfactuals are gaining attention to address the lack of robust flood frequency analysis in small catchments. However, the credibility of counterfactual scenarios decreases with the distance rain fields are transposed across space. We limit that distance by a local counterfactual search design and compare the corresponding scenarios to recently published results from long-distance transpositions. We then put all scenarios into context with 200-year return levels and with flood peaks simulated for the June 2024 flood event in southern Germany. We conclude that local counterfactual scenarios are transparent and credible and could complement the anticipation of low-probability events.