Research on a Dynamic Flood Risk Evacuation Model Based on Flood Information and Road Network Reconstruction

Static flood evacuation plans frequently fail during levee breaches because dynamic floodwaters rapidly submerge pre-designated routes, trapping affected populations. This study aimed to develop a dynamic evacuation route planning model by coupling hydrodynamic flood simulation with road network reconstruction for levee breach scenarios. A coupled one- and two-dimensional hydrodynamic model simulated breach flood dynamics, while road network topology and travel-time weights were dynamically updated based on water-depth-dependent vehicle speed attenuation. Using the Dijkstra algorithm to calculate stage-specific optimal routes, the framework was evaluated in the Huayang River Flood Retention Area (HRFRA) along the Yangtze River under a 300-year flood scenario. Results show that: (a) Static routes failed at a rate of 51.5% within 24 h, with 22.7% failing within 6 h. Dynamic route failure rates were 4.5% and 31.8% over the corresponding periods. (b) For 66 villages requiring external relocation, the model dynamically adjusted shelter destinations as roads became inundated. For Tongxing, switching shelters from Qianling (0–21 h) to Chengling (21–57 h) and Liangquan (57–63 h) extended the available window to 63 h, compared with 21 h under static planning. (c) Ten villages, including Qiaobei, scheduled for evacuation after 24 h, lost all viable routes within 9 h, highlighting the need to schedule evacuation batches based on route cutoff times rather than flood arrival times. By integrating network accessibility with flood dynamics, the model improves evacuation planning and supports emergency management.