Storm Hans was a significant system that impacted Norway and Sweden between 8th -12th August 2023. Estimated damage form the storm is estimated at just under 1 billion euros. A key event during the storm was the overtopping and failure of a dam at Braskereidfoss.
Braskereidfoss hydroelectric dam, owned by Hafslund Eco overtopped during daylight hours on 9th August 2023 when the flood gates remained at 20% capacity, despite increasing water levels overnight. The dam was unmanned and the operations centre in Lillehammer was overwhelmed by multiple situations in the rain event. Attempts to rescue the situation were abandoned as overtopping also inundated the hydroelectric plant, removing back up power systems. During the day, the Norwegian Army was deployed with consideration given to a controlled failure through explosives. The dam overtopped and the embankment subsequently eroded.
A 2018 risk assessment noted the scenario that evolved as a risk and accepted that risk just 7 months prior. There was no technical failure according to the final investigation report with a lack of redundancy, staffing and system testing identified as key elements of a systemic failure. The case study has a full investigative report with over 30 learnings available.