This study focuses on developing new design principles for flood protection in small, rainfall-driven catchments of the Weinviertel region (Lower Austria). Due to climate change, with increasing heavy rainfall and droughts, the retention and infiltration of surface runoff are becoming more important than traditional drainage systems. The goal is to design retention basins that provide flood protection equivalent to a 100-year event (HQ100), based solely on infiltration. Current models and design methods, which were primarily developed for channel-based (fluvial) flood events, do not sufficiently capture hillslope processes. The study integrates empirical data from the Hydrological Open Air Laboratory (HOAL) in Petzenkirchen and additional monitoring sites with stochastic simulations to better estimate event probabilities and runoff generation mechanisms. Based on these findings, applicable design rules will be developed for the Weinviertel and may inspire cost-effective, decentralized solutions that also support agricultural water management.