Modeling Direct Economic Loss of Residential Building Contents Induced by River Flood and Storm Surge: A Case Study on Typhoon Rammasun in Haikou City of China

Typhoon often brings heavy rainfall, floods and storm surges to estuaries and may cause devastating disaster loss, especially in the downstream coastal urban areas, so a timely modeling of disaster loss is of great importance to emergency management. However, the complexity of interaction between river flood and storm surge imposes great challenges to the simulation of coastal flood in urban cities. At the same time, the local characteristics of building contents such as their types, values and vulnerabilities in different cities may also vary greatly. Haikou city, located in Hainan Island of China, was flooded due to the cascading effects of the upstream flood from Nandu River basin and the strong storm surge caused by strong winds of typhoon Rammasun during July 18 to 20, 2014.

In this study, firstly, the water from Nandu River was simulated with hydrological model and one-dimensional hydraulic model, and the coastal storm surge was modeled with a numerical surge model. The outputs of these models were used as the boundary conditions of two-dimensional hydraulic model, coupled with SWMM to reflect urban surface flow. Based on the above models, the maximum flood depth in Haikou city were derived. The inundation depth of Nandu River Estuary and riverside area is about 4 meters, while it of urban areas is relatively shallow. Secondly, the boundary of all the buildings in Haikou city and their geographic distribution were collected, and the values of contents were estimated building by building based on questionnaire survey data. Finally, based on the vulnerability curves developed in the past study, the direct economic loss of residential building contents were estimated. The results can provide a firm basis for the prediction of future loss before TC landing.