By using radar raingauge images and its animation, a short-term prediction method of rainfall intensity is proposed, and the precision and applicability of Thiessen method to estimate the average-rainfall-depth over a watershed is investigated. The short-term rainfall prediction through judging the animation by eyes shows good agreement with the rainfall intensity observed by raingauges installed on the ground. Further, we estimated the average-rainfall-depth over a watershed from the radar, and compared its results with the average-depth calculated by the conventional method using Thiessen method. Finally, we clarified the effects of deviding numbers of a watershed in Thiessen method on the estimation of average-rainfall-depth.

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At first, the radar parameters (B and β) are identified under the criteria of least squares at each observation point for each rainfall event. The characteristics of the optimal parameters are analyzed. Secondly, a real-time prediction method of ground rainfall by the extended Kalman filter (EKF) using intensity of radar reflectivity factor is proposed. In this prediction method, the relation of the radar parameters obtained from above analyses is taken into account. To study the effectiveness and the various characteristics of the prediction method, it is applied to hourly ground rainfall data for 6 rainfall events. As the results, it is shown that the methodology is accurately able to conduct real-time prediction of ground rainfall using radar data.

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A geographic information system in hydrologic modeling, BGIS (Basin Geomorphic Information System) is presented for topographic modeling of a river basin. BGIS is a set of computer programs which model natural landscapes using TIN-based DEMs and partition a catchment taking account of the direction of water flow for dealing with water movement one-dimensionally. BGIS is applied to some watershed basins in Japan, and it is confirmed that the system is a powerful tool to examine the effect of spatial variability of topography on runoff characteristics.

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In a river bend, the bed is scoured deeply near the outside bank due to the action of relatively strong secondary current, which results in the bank erosion. In this study, a series of square bar elements were set diagonally on the side wall to generate secondary current artificially and the flow structure past the bars was measured extensively to clarify the structure of the generated secondary current. As a result, the original secondary current which is due to the centrifugal force in the bend was found to be controlled effectively if a series of bars are set on the ouside bank in bends. The possibility to prevent the local scour near the outside bank was verified.

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Flow fields of open channel flows with adverse pressure gradients were measured by a X-type hot-film anemometer. Mean velocity profiles of the inner- and outer-region are expressed by the log-wake law. The wake strength parameter ∏ was quantified experimentally as a function of the normalized pressure gradient parameter β. The equation of motion as well as the continuity equation, assuming that the velocity profile is similar at all distances downstream, are solved to obtain the Reynolds stress distribution. The proposed method can predict the Reynolds stress distribution satisfactory as long as the parameter β are moderately small.

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Open channel flows over a wavy bed are investigated theoretically by using the perturbation method for the open channel flow equations. The depth averaged momentum equation including the effect of vertical acceleration is applied to the analysis of free surface profiles and bottom shear stresses. Considering the irrotational condition of flow far from the bottom and the acceleration/de-acceleration effect near the bottom, the local change of the velocity distribution is introduced through the depth integration of the momentum equation in the flow direction. The 1st and 2nd order solutions are derived and are compared with the previous experimental results of depth and bottom shear stresses.

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It has been known that shear instability generates large horizontal vortices at the junctions of a main channel and flood plains in two- stage channel. A series of laboratory tests were performed by varying the main channel width, and the tests were conducted for 3 cases of water depth. Fluid velocity and water surface elevation were measured by using laser-Doppler velocimetry and capacity- type wave gage, respectively. It was found that two arrays of vortex streets become very stable at b/H=5, in which b is main channel width and H is main channel depth. The Reynolds stress at the junction shows a peak value at b/H=5 for all cases of water depth. The wavelength of vortices was predicted successfully in terms of linear shear instability analysis.

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Accelerating and decelerating flows, i. e., flows with the streamwise non-uniformity of bed boundary, are greatly affected by the pressure gradients. It is of both fundamental and practical importance to investigate the effects of various pressure gradient on the turbulent structures in open-channel flows in order that the statistical characteristics such as mean velocity, turbulence intensity and shear stress are largely different from the uniform open-channels and zero-pressure gradient boundary layers. Near-wall region which consists of viscous sublayer and buffer layer in open-channel flows over a sine-formed wavy bed was accurately measured by means of a two-component and fiber-optic laser Doppler anemometer (LDA); the effects of pressure gradient produced by such a bed shape and free-surface profile were discussed with respect to profiles of turbulence characteristics.

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The analysis of beach survey data collected from 1983 to 1993 on the Shizuoka coast showed the existence of a sand body propagating to downcoast by the velocity of about 233m/yr around detached breakwaters. A numerical model predicting the movement of sand body was developed. Sand movement in the shoreward and offshoreward regions of detached breakwater is modeled separately and time lag requiring for littoral drift to pass through the location of detached breakwater was taken into account. Predicted velocity of this sand body was 230m/yr and it agreed well to observed one. Predicted profile changes around detached breakwaters quantitatively agreed well with the observed ones.

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In this report, first of all, the method to deduce the biological class (saprobic zone) from physical and chemical items of water quality of rivers was developed. Then, the synthetic evaluation of water quality or water pollution level of rivers from both the physical and chemical indexes and the biological index was done by the principal component analysis method (PCA). The first principal component of PCA was proved to be available for the evaluation of water quality or water pollution level of rivers. Using the physical and chemical variables and the biological variable duduced by the manner described above, the synthetic evaluation of water quality of rivers was done by PCA, and the first principal component was found to be the same factor as mentioned above.

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Lately, Genetic Algorithms are used for optimization problems. This algorithm based on the theory of evolution creates the suitable individual by repetition of three operators of selection, crossover and mutation. This method is applied to the optimal refuse collection and transportation plan in which several refuse collection trucks transport the municipal solid waste to the treatment plant site in minimum time. The results shows the availability of Genetic Algorithm to determine the optimal transportation order.

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Experimental study of the effect of particles accumulation on the drag force in solid-liquid two-phase flow is made. The experiments are performed in a vertical tube in which particles have only fluctuation velocity due to the balance between gravity and drag forces felt by the particles in the flow. The experimental data are examined by using the formula of the fluid/particles interaction force developed by the authors, as the result, the relation among the accumulation effect, the particle concentration and relative density of multiphase flow is clarified.

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A new system to generate arbitrary-profile oscillatory flow has been developed with a piston-type closed conduit. To remove vibration due to inevitable friction between the piston and tank wall, the present system allows a small gap to exist between them. To theoretically predict the deformation of the output velocity profile due to the gap, unsteady Bernoulli's and continuity equations were used for the formulation. The analytical and numerical solutions of the formulated equations show good agreements with the experimental data. With this prediction method, an output velocity profile with arbitrary profile as a target signal was confirmed to be generated with high accuracy.

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