A prototype warning system for surface water floods at Swiss campgrounds

Surface water foods (SWF) regularly cause significant damage in Switzerland, particularly during high-intensity rainfall events associated with thunderstorms. Despite their impact, operational warning systems that address SWF at the local scale and meet the needs of specific user groups remain scarce. This study presents a co-creation approach to developing an impact-based, location-specific warning system for SWF at Swiss campgrounds. Collaborating with nine campground managers, we established a value chain from meteorological forecasts to end-users by linking forecast data with location- and vulnerability-specific thresholds to identify damage-relevant precipitation events. Two interview rounds and a test phase in summer 2025 guided the iterative development of a prototype warning system. Interviews revealed diverse risk perceptions, differing action thresholds, and the need for accessible, user-friendly communication. The final prototype issued SMS alerts when local thresholds were exceeded and provided a mobile-friendly website for further information. User feedback indicated that warnings were generally timely and relevant, although preferences and information needs varied considerably across participants. The co-development process was key to defining thresholds, lead times, and visualizations that convey uncertainty effectively. It highlights the need for user-tailored systems and provides a transferable framework for participatory, impact-based early warnings using open forecast data and real-time geoservices.