A complete river and coastal disaster prevention analysis should include comprehensive hydrological analyses from the upstream tributaries to the downstream estuary of the basin. The analyses are carried out by using the digital elevation model for watershed geomorphologic characteristics extraction and then developing the watershed runoff routing model for rainfall-runoff simulation, one-dimensional channel-flow model for flood wave transport simulation, two-dimensional inundation model for floodplain inundation simulation, and the storm surge model to provide the tide level forecasting. Considering that the flooding in the downstream urban areas will start from the surcharge of the drainage sewer, a combined drainage model, including a one-dimensional underground sewer-flow system and a one-dimensional street-flow system, is also developed for urban flooding simulation. Since providing immediate warning information is the most important thing for a flood early warning system, we strive to develop computational efficient models to meet the requirement of the competent authorities. Currently, we have built up the kinematic-wave-based geomorphologic IUH model for watershed runoff simulation, an implicit-Preissmann dynamic-wave model for flood channel routing, a 2D non-inertial wave model with modified MacCormack recurrent algorithm for inundation simulation, a street-sewer 1D/1D combined model for urban flooding warning, and a back-propagation neural network model for storm surge forecasting. An operational system will be developed to integrate all the models on a platform in the near future for real-time disaster prevention work.
