Optimization of Stormwater Security Patterns in a Hilly City Informed by Runoff Processes: A Multi-Scenario Land-Use Simulation Approach

Rapid urbanization alters natural runoff processes in hilly cities and increases flood risk, yet translating runoff-process understanding into coordinated land-use decisions remains challenging. Multi-scenario land-use simulation for 2035 linked runoff-process understanding with stormwater security pattern optimization. In Changsha, land use, natural runoff channels and low-lying areas informed flood-control constraints in the Patch-generating Land-Use Simulation (PLUS) model. Inundation was simulated by coupling the Soil Conservation Service curve number (SCS-CN) model with an equal-volume inundation algorithm. Qualitative comparisons of simulated inundations with historical records showed good spatial agreement. Under a 100-year, 3 h rainfall scenario, new construction land within high-risk zones covered 20.58, 6.14 and 21.70 km2 in the baseline, flood-safety, and economic-development scenarios, respectively. An integrated plan balanced flood safety and economic development, reducing this overlap to 6.45 km2, 68.7% below baseline. Its high-risk area was 319.24 km2, with a total inundation volume of 715.89 million m3. The optimized pattern comprised seven corridor levels, 26 lakes and reservoirs, 27 low-lying control zones and 197.78 km2 of other inundation zones. The latter two categories had an estimated combined storage requirement of 386.57 million m3. These comparisons provide a planning basis for optimizing stormwater security patterns through blue–green infrastructure in hilly cities.