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In Tokyo metropolitan area, flood risk is increasing due to social and environmental conditions including concentration of population and industry etc. Small urban watersheds are at a high risk of inundation by river flooding and/or inner water induced by heavy rainfall in a short time. To estimate river water level accurately in urban small rivers, it is critically important to conduct precise runoff analysis by using spatiotemporally distributed rainfall data. In this study, a runoff analysis was conducted with spatiotemporally densely distributed X-band MP Radar (X-band multi-parameter radar) data as input for storm events occurred in upper Kanda River, a typical urban small river in Tokyo. Then, SCE-UA method, one of global optimization methodologies, was applied to identify the parameters of the storm runoff model. The results revealed that urban storm runoff was predicted accurately using X-band MP radar map supported by optimized runoff model.

Wave forces on a structure installed on a submerged breakwater have been measured to investigate their characteristics. It has been observed that the impulsive wave force due to wave breaking acts on the structure located the vicinity of the leading crown of the breakwater. Them agnitude of the impulsive wave force has been revealed to be much larger than those of then on-breaking waves. Thet imev ariation of the impulsive wave force is well evaluated with the Morison equation by adopting the velocity and acceleration at the front face of the structure. Moreover, it has been revealed that the drag coefficients decrease for higher values of KC approaching the constanv talue. On the other hand, the inertia coefficients are almost constant for all the tested values of KC.