Storm surges from tropical cyclones, as one of the most devastating natural hazards in Shanghai, have caused considerable personal injury and property damage in the history. A scenario-based study that investigated the storm induced flood potentials in Shanghai coastal area was conducted. Based on the probability analysis for several gauge stations, the findings show that due to the high standard seawall, it is less likely to occur overtopping inundation in the short term. Therefore, two vulnerable sections of seawall and six kinds of storm surge barrier bursts scenarios were built. Comparing the local land elevation with the flood levels of different return periods, flood scenarios with return periods of 20, 50, 100, 200, 500 and 1000 years were designed to cover the probable situations. The shape of the flow hydrographs at the boundary gauging stations for various return periods was derived based on 9711 typhoon induced flood event where hourly flow boundary conditions were available. To reduce the computational costs of the simulation, the design flood scenarios were represented with 20 hours tidal hydrographs, which include two rising phases and two falling limbs. The topographic contours (0.5 m intervals) of Shanghai were interpolated to generate a DEM with a grid cell resolution of 50 m. These provided the flow and topographic boundary conditions for the model simulations. A well-established 2D flood numerical model (FloodMap) was used to predict the flood dynamics and inundation process. Subsequent analysis using Geographical Information Systems (GIS) was employed to illustrate the spatial and temporal distribution of flood-prone areas under different scenarios. The results indicated that, 1) maximum inundation depths were reached in all simulations at approximately the second to third hour, decreasing afterwards as the stage recedes. 2) Inundation area for each scenario increased throughout the simulation, even during the receding limb of the hydrograph. 3) The maximum inundation extents and depths increased with the increasing return periods. 4) Flooding from levee breach only caused local inundation. It can be concluded that the impact of storm flooding was not particularly high in Shanghai at present situation with the protection of high standard dike systems. However, extreme events caused by global climate change should be considered in future studies.

Scenario modeling and risk assessment of natural disaster is one of the hotspots of disaster research. However, urban natural disaster risk assessment, so far, is lack of common procedures and program. This paper selects rainstorm water-logging as research disaster, which is one of the most frequent occurring hazards in most cities of China, and sets up a small-scale based integrated methodology for hazards risk assessment of rainstorm water-logging, taking Jing\'an District in Shanghai as an example. Based on the basic concept of disaster risk, this paper applies scenario modeling to express the risk of the small-scale urban rainstorm water-logging disasters in different return periods. Through the analysis of hazards, vulnerability and exposure, we simulate different disaster scenarios and propose a comprehensive analysis method and procedure for the small-scale urban storm water-logging disaster risk assessment. A grid-based GIS approach, including urban terrain model, urban rainfall model, urban rainfall model and urban drainage model, was applied to simulate inundation area and depth. And then, stage-damage curves for residential buildings and contents were generated by the loss data of water-logging from the field surveys and the insurance company, which were further applied to analyze the vulnerability, exposure and loss assessment. Finally, the exceedance probability curve for disaster damage was constructed by using the damages of each simulated event and its respective exceedance probabilities. A framework was also developed for coupling the water-logging risk with the risk planning and management through exceedance probability curve and annual average of water-logging loss. And this is a new exploration for small-scale urban natural disaster scenario simulation and risk assessment.