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Development and Application of Coupled One-Dimensional Unsteady River Flow Model and National Taiwan University Cellular Automata Flood Inundation Model
Unsteady flow,2D flood inundation model,Coupled model,Levee overtopping,
|Publication Year :||2021|
|Abstract:||近年來流域內的河川水位因暴漲而溢堤，導致堤內地區的嚴重淹水災害增加。若能有快速且精度良好的流域淹水模式，將可提升流域尺度的災害應變能力。現有的NTU-CAFIM模式(National Taiwan University Cellular Automata Flood Inundation Model)經過發展，已可提供快速且精度良好的都會區地表淹水模擬，如能將其與一維河川變量流模式進行耦合，便可提供即時的流域淹水模擬，對於防災應變有所助益。|
In recent years, serious flooding in areas near the river due to river embankment overflowing is increasing. To promote disaster prevention and protection for the whole river basin, a fast and accurate inundation simulation model is required. The existed National Taiwan University cellular automata flood inundation model (NTU-CAFIM model) can fastly and accurately provide a prediction of flooding in urban areas, thus it is appropriate to be coupled with the 1D unsteady river flow model to provide real-time forecasting of flooding in the river basin.
In this study, the 1D unsteady river flow model (RFM) is coupled with the NTU-CAFIM model (OFM), so that water can be dynamically exchanged through embankments of each river reach. Rules to describe exchanged water are developed for coupling the RFM and OFM, including the correspondence of different spatial resolutions between riverbank cells in the OFM and river reaches in the RFM, and the calculation of exchanged volume between riverbank cells in the OFM and river reaches in the RFM. In particular, the exchanged volume between the RFM and OFM through embankments along each river is calculated by either free or submerged weir flow formulas.
To verify the water exchanging rules in this study, two case studies are selected, and the coupled model is compared with the HEC-RAS model by indicators such as Nash-Sutcliffe efficiency (NSE), accuracy (ACC), and sensitivity (TPR). Based on the simulation results of a small-scale ideal case and the case of the Severn River Basin in the United Kingdom with an area of 24km2 and actual complex terrains. The simulation results of the coupled model in the hydrographs of water level in river sections, the hydrographs of flow rate in river sections, the hydrographs of water levels in two-dimensional overland flow, the hydrographs of water overflowing, and the maximum flooding area are very similar with the HEC-RAS model. Furthermore, in the ideal case and the real case of the Severn River Basin, the coupled model is 47% and 41% faster than the HEC-RAS model. The above results indicate that the coupled model is as accurate as the HEC-RAS model with a significant reduction in its computational time. Hence, it is concluded that the coupled model has considerable potential to be applied to real-time simulation of flooding in the river basin.
|Appears in Collections:||生物環境系統工程學系|
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