Study on the flood weakness of cities and the flood emergency management system

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The mechanism of inundation occurrence by heavy rainfall is studied for the Neya river basin in Osaka Prefecture. The studied river basin is divided into four parts ; (1) mountainous area (2) river network (3) sewerage network and (4) drainage basin. In (1), runoff discharge is calculated by the kinematic wave model.In (2), the method of characteristics is applied to one-dimensional unsteady flow analysis. In (3), the analysis based on the continuity equation, considering the upper limit of drainage is conducted. In (4), twodimensional inundation flow model by the unstructured meshes is applied. The validity of simulation results is confirmed by the comparison with the recent inundation records. Through the simulation analysis, the dangerous zone of inundation and the effect of flood control facilities are discussed.With regard to the inundation in underground space, a mathematical model based on storage pond is developed. In this model, underground mall and subway are treated by the c … More ombination of multiple storage ponds, and the water volume exchange between adjacent ponds is simply treated by overflow formula or discharge formula. This model is applied to Umeda underground mall and adjacent subways in Osaka. The results show that this model can be applicable to the real compound underground space. Also, by the simulation analysis, the effect of ground level and inundation water depth on water intrusion into underground space is discussed, and the inundation water spread in underground space is examined.As for the emergency management and countermeasures against urban flood, the heavy urban flood in Fukuoka and that in Nagoya (in Toukai district) are taken and the characteristics of these urban floods are summarized. Through the studies, it is pointed out that many of cities in Japan tend to suffer flood disasters by overflow from the river or the sea or by heavy rainfall under the natural and social severe conditions of their own, and that their flood weakness becomes more conspicuous as urbanization proceeds. While, the significance of non-structural countermeasures is discussed and emphasized such as warning system and information transmission, evacuation plan and educational activity. Less