Improved urban flood risk assessment based on spontaneous-triggered risk assessment conceptual model considering road environment

Abstract

Urban flood risk assessment is an important tool for urban disaster management. The current research mainly considered area itself as the evaluation object. Urban road networks are extremely vulnerable to floods as a basis for all socio-economic activities in the city. However, most studies on road environmental risk assessment only took road itself as the evaluation object and did not consider potential regional system risks such as traffic jam caused by road inundation. Based on this, this study proposes a spontaneous-triggered risk assessment (STRA) conceptual model that comprehensively considers the spontaneous risk (SR) caused by the subregional hazard, socio-economic exposure, and triggered risk (TR) from the cross-subregional traffic jam or interruption caused by the road inundation in the evaluated subregion. Taking Haidian Island in Haikou as an example, six indices were selected for the SR assessment based on the combined weight-gray fuzzy comprehensive risk assessment method. The maximum mean inundation depth of road (RMD), maximum inundation duration of road (RID), road betweenness centrality (RBC), and number of road bus lines (RBL) were selected for the TR assessment. Total flood risk (FR) of the study area was obtained by combining the two. The results indicate that, compared with the traditional SR, the highest and higher risk subregions are more concentrated in the study area center, and the risk of the outer ring subregions is reduced overall after considering the TR. According to statistics, the FR level of 68 subregions is lower than the SR level, most of which are in the outer ring of the study area, and the FR level of 17 subregions is higher than the SR level, most of which are located around the intersection of Haidian Fifth Road and People Road. The study outcomes provide a novel approach for flood risk assessment.