Assessing pluvial flooding risk in urban areas with high spatial heterogeneity using a fused physically-based and data-driven framework

This study developed an integrated urban flood risk assessment framework for cities with significant spatial heterogeneity, combining differentiated hydrological-hydrodynamic modeling with complementary grid-based (ISM) and drainage zone-based (CM) risk assessment approaches.

The main conclusions from the study are as follows.

1.  Pronounced spatial heterogeneity across the urban area influences flood risk. Pipeline density shows marked directional variability, with regions Z3 and Z14 in eastern areas displaying highest densities while remaining sparse elsewhere. 
2. Drainage infrastructure exhibits substantial vulnerability even during frequent rainfalls, with 60.89% of pipelines experiencing hydraulic overload during 1-year return period, increasing to 64.89% under 100-year return period rainfall, according to the pipeline capacity analysis. 
3. Grid-based ISM risk analysis reveals a 94.47 ha expansion of very high-risk areas from the 1-year to 100-year return period, while low-risk zones decrease slightly from 92.19 to 88.24%. CM-based risk analysis shows that low-risk zones contract from 57.7 to 26.2% of the study area, with high-risk zones concentrated in the central-western regions.