ICARIA: Impacts of compound storm and flooding events in a mountainous region

Globally, natural disasters have increased significantly in recent decades, with the CRED and UNDRR reporting 7,348 events between 2000-2019 [1]. These disasters caused 1.23 million deaths, impacted over 4 billion people, and resulted in economic losses of approximately $2.97 trillion. A large proportion of these disasters were climate-related, such as heatwaves, droughts, and floods. If the current warming trajectory continues, failure to meet the Paris Agreement goals could lead to a 10% loss in global economic value by 2050 [2]. In response, the ICARIA project aims to enhance understanding of climate-induced, complex disaster impacts and develop sustainable adaptation strategies. Focusing on critical infrastructure at risk from climate change, we study the Pinzgau region of Salzburg, with particular emphasis on fluvial flooding and storm hazards under changing climatic conditions. To assess these hazards, global CMIP6 models were dynamically downscaled using two regional climate models (WRF and CCLM) with resolutions of 5 km and 2 km, respectively, for the scenarios SSP1-2.6 and SSP5-8.5. Climate indicators, such as maximum precipitation (rx1day) and wind gusts (wsgsmax), were analysed to capture both historical (1981-2010) and future hazard trends. Observations were validated against the high-resolution CHELSA reanalysis dataset. Hydrological modeling of fluvial flooding used the physically simplified SFINCS model to simulate high-resolution flood dynamics (up to 1 m) for extreme rainfall events. Future projections will incorporate downscaled climate scenarios to estimate hazard shifts under varying emission pathways. The frequency of compound events will be analysed in the historical period as well as in a changing future. Furthermore,  the change in the regions vulnerability after such an event (dynamical vulnerability) shall be investigated and exploited. Initial results indicate significant discrepancies in temperature and precipitation patterns between models for the Salzburg region. For 1981-2010, both models show cold biases compared to CHELSA, with deviations of 1°C in the north and up to 5°C in the southwest. The underestimation of maximum temperatures aligns with a notable overestimation of annual precipitation, particularly in the coarser WRF model (5 km resolution). Precipitation patterns are more consistent in CCLM (2 km resolution), which shows smaller deviations overall. Climate change signals (CCS) for Salzburg project substantial increases in maximum temperatures, with localized rises exceeding 6°C under SSP5-8.5. CCLM driven by EC-EARTH shows more pronounced changes compared to WRF driven by MPI. Annual precipitation trends differ: while WRF predicts increases of up to 15% under SSP5-8.5, CCLM outputs suggest slight decreases. Preliminary hydrological modeling of an extreme rainfall event shows a 12-hour lag in peak flood depths compared to local station data but achieves strong alignment in maximum flood depths, demonstrating SFINCS’s potential for accurate flood impact assessments. These findings underline the importance of multi-hazard climate risk assessments to inform disaster risk reduction and adaptation strategies, particularly for critical infrastructure in vulnerable alpine regions. 

[1] https://www.undrr.org/publication/human-cost-disasters-overview-last-20-years-2000-2019

[2] https://www.swissre.com/institute/research/topics-and-risk-dialogues/climate-and-natural-catastrophe-risk/expertise-publication-economics-of-climate-change.html