Development of a novel spatiotemporal propagation function for flood risk prediction in the Daqing River basin, China

Study region The Daqing River basin in China has been frequently affected by floods. Flood risk exhibits both temporal and spatial interdependence, driven by hydrological memory effects and cascading flood processes within spatially connected river systems. Study focus The study elucidated spatiotemporal propagation patterns of flood risk and developed a novel spatiotemporal propagation function for risk prediction. Initially, flood risk in twenty-two subbasins of the Daqing River was evaluated by integrating hazard, exposure, vulnerability and mitigation capacity. Markov-based state transition diagrams were subsequently employed to calculate flood risk propagation probabilities, distinguishing temporal and spatial risk propagation patterns. Moreover, a spatiotemporal risk propagation function incorporating risk propagation effect and flood control infrastructure interference was proposed to predict flood risk. New hydrological insights Results indicate pronounced spatial heterogeneity in flood risk across the Daqing River basin during 2000–2020, with high-risk areas concentrated in northern region and eastern edge. Temporally, interannual flood risk variation in each subbasin was driven by mid-high and high, and low and medium grade transitions. Spatial propagation between adjacent subbasins was dominated by risk attenuation across 44.8% of adjacent subbasins. The spatiotemporal propagation function achieved an average prediction accuracy of 90.5% and disentangled temporal and spatial propagation contributions to flood risk. Additionally, five reservoirs and flood detention areas in the central-eastern basin reduced risk propagation by 26.4% and 30.3% via their buffering capacities.