An overview of controlled sediment flushing operations: Perception, issues and management strategies across the European Alps

Study region: European Alps Study focus: The increasing demand for water and renewable energy, along with climate-induced hydrological changes, is driving the development of strategies to counteract reservoirs siltation, including sediment flushing. This review first examines the social perception of this desilting technique, then outlines related current legislation, key research progress, and ongoing criticisms, with specific focus on the European Alps. It also compares alternative sediment management strategies, highlighting their pros and cons. New hydrogeological insights from the region: Due to societal concerns and stakeholder pressure, flushing operations have evolved into more controlled processes, reducing fish mortality and long-term impacts over river ecosystem. As a result, regulations have been updated, generally requiring environmental considerations in support of desiltation strategies. However, fragmented management of freshwater resources-particularly water and sediment flows-still hinders more ambitious environmental goals. While sediment flushing remains a key technical solution, further advancements are needed in flushing methods, post-flushing mitigation, and planning and monitoring practices. In the study region, research on this topic is limited, mostly focusing on specific operational aspects and case studies. To our knowledge, this is the first review offering a comprehensive analysis that integrates social, technical, and legislative dimensions, providing a foundation for improving reservoirs sediment management by flushing.