Why structural solutions for flood control should be adapted to climate change?

Anthropogenic activities in intensively managed landscapes have altered mechanisms of runoff generation and flood regimes. Despite utilizing hydraulic structures for decades to control floods, their expected performance under the varied frequency or intensity of extreme precipitations due to climate change may be less certain. This study aimed to examine this hypothesis by employing both remote sensing and field data in the Imamzadeh Davood watershed in Central Northern Iran, which experienced a devastating flash flood in July 2022. To this end, we collected data on river morphology, the structural characteristics of 18 check dams, and sedimentation patterns by surveying the main river path. We also processed satellite imagery to track long-term land-use and land-cover change. Finally, we explored the distinct role of extreme precipitation in intensifying the occurred flood incident using recorded data from synoptic stations. Our findings revealed an unprecedented > 100-year return period precipitation event in the catchment, with devastating consequences that underscore the escalating impact of heavy rainfall due to climate change in many regions. In-situ observations revealed that all 18 check dams were destroyed between 17 and 100% during the flood event, while upstream check dams showed a higher degree of destruction. The external stability analysis demonstrated that under static forces, 100% and 62% of the check dams were potentially resistant against sliding and overturning, respectively. However, given the observed destruction of all check dams and high deposition depth of sediment in the river corridor, our further analysis by considering dynamic forces and rock impact indicated that the shock imposed by the unprecedented debris flow was responsible for the cascade failure of check dams from upstream to downstream. These findings highlight the need to revisit the design principles of hydraulic structures under the impact of climate change to increase the resiliency of flood control systems.