A Prototype Warning System for Surface Water Floods at Swiss Campgrounds

Surface water flooding (SWF) results from heavy precipitation that cannot penetrate the ground and thus flows over open terrain until it reaches a watercourse or drainage system. It poses a major hazard and can significantly damage houses and infrastructure. In Switzerland, 62% of all buildings are vulnerable to SWF, and nearly 50% of all flood-related insurance damage claims can be attributed to SWF. Despite the clear relevance of SWF and its potential high impact, it has not received the same attention as fluvial floods.

Mitigating the high risk of SWF requires not only improved forecasting capabilities but also solutions that are effectively embedded in real-world decision-making contexts. Campgrounds serve as an ideal environment to explore user-centered warning solutions due to their high exposure to flooding and limited protective infrastructure. The presence of foreign guests, who are often unfamiliar with local weather risks, further highlights the need for clear, actionable communication. To lay the foundation for a system that meets the actual needs and decision-making processes of the end users, we conducted interviews with campground managers across Switzerland. These conversations provided valuable insights into their experiences with past flood events, current strategies for monitoring weather conditions, practical challenges faced during heavy precipitation events, and expectations towards useful warning systems. This qualitative phase also helped identify relevant precipitation and probability thresholds, and supported campground managers in interpreting forecast information through a better understanding of the underlying science.

In the summer season 2025, a real-time test phase will evaluate the practical effectiveness of the warning system under operational conditions. Automated alerts will be triggered for participating campground owners when forecasts exceed the predefined precipitation thresholds. To assess the system’s accuracy, post-event surveys and site inspections will be conducted to evaluate whether these forecasted conditions aligned with actual surface water impacts, such as site accessibility, infrastructure damage, and evacuation decisions. The data collected from these assessments will enhance our understanding of the precipitation thresholds most relevant to operational warnings and help refine the system’s effectiveness.