A flood runoff model for small urban watersheds with detention basins is proposed. The proposed runoff model is based on the Nash model. The storage coefficients of the Nash model are estimated by the kinematic wave model for rural areas and built-up areas respectively. Outflow from detention basins are calculated by the storage routing method. We applied the present runoff model to two small urban watersheds and obtained good results. And we could estimate the flood control effects of detention basins by comparing the hydrographs calculated by the present runoff model for urban watersheds with and without detention basins respectively.

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Non-equilibrium bed-load transport model is constituted by pick-up rate and step length, and it is required to estimate these two against the hydraulic condition reasonably. This study deals with the pick-up rate, which is defined as the probability density for a bed-material particle to be dislodged from a bed per unit time. The pick-up rate is here formulated as the reciprocal of the time for a particle to be dislodged from a bed by using the equation of motion with probabilistic approaches to fluctuating tractive force and the bed surface irregularity. The present study particularly calrifies the effects of grain size of bed material and variation coefficient of tractive force on pick-up rate.

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Thermosolutal convection in heat-salt stratification system is numerically simulated by using a turbulence closure model. The density field considered here is a simple double-diffusive system composed of linear salinity gradient heated from below. Development of multi-layers structure, merging processes of neighboring convective layers, profiles of the turbulent second order terms and other characteristic convective motions are successfully reproduced. The present analysis enables us to predict and examine not only mean density fields but also turbulent structures which have not been discussed in preceding studies so far.

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The arrangement of groins in meandering rivers has been mainly determined on the basis of hydraulic model experiments and engineering judgement. These method have a weak point not to be able to determine groin arrangement to river courses with arbitrary bank alignment. At the standpoint that the numerical model and the hydraulic model test are complemental to each other, a three dimensional numerical model was developed to decide hydraulically optimum arrangement of the groin in meandering rivers. The result of calculation showed very good coincidence to that of the authors' large-scale hydraulic experiments with regard to the three dimensional flow field and the river bed variation, irrespective of flows with groins and without groins. This model also enabled us to decide the optimum arrangement of the groins to river with arbitrary bank alignment.

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The non-equilibrium bed-load transport process under the time-dependent shear stress is explained well by the convolution integral model along the temporal axis proposed in this paper, which is constituted by the pick-up rate and the moving period. In order to evaluate the constituent elements of the model, first, the numerical simulation of the dislodgment process is executed. Based on such a simulation, the effect of acceleration on the pick-up rate is clarified. Secondly, the numerical simulation of the moving process is executed to estimate the characteristics of the moving period. Finally the simulation are applied to the oscillation-current coexisting flow. The transformation process from the pick-up rate to the deposit rate is simulated accurately by the present simulation, and the applicability of the present study is emphasized.

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Horizontal, periodic vortices generated at the boundary of vegetated area along river bank was studied in terms of linear stability analysis using Rayleigh equation. A dimensionless angular frequency, at which an infinitesimal disturbance takes the maximum growth rate, is found to be uniquely correlated with a dimesionless parameter for the vegetation density. Laboratory tests were also performed, in which the periodic vortices were observed by dye injection into the flow field and the period was measured using a wave gage. The measured period of vortex generation was explained very well by the linear stability analysis. The present study reveals that the periodic vortices are generated by instability induced by the existence of an inflection point in the lateral distribution of depth-averaged flow velocity.

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Coherent structure in turbulent open channel flow in corners is investigated using flow visualization. In the flow visualization, a sheet of laser light, which illuminated fluorescent dye tracer in streamwise, transverse, and plan view, was used. Some new aspects of the coherent structure are inferred from this experiment. The “wall streamwise vortices” on both walls are arrayed alternately, and concentrate to the original regions respectively, where the region of low wall shear stress are formed. And the wall streamwise vortices seem to play important role to form instantaneous secondary flow.

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This study proposes the new model for calculating the changes in a probability distribution of irregular wave height on sloping beaches. Experimentally measured properties of irregular wave height changes in all the processes such as shoaling, breaking and decay after breaking on different slopes are taken into account in the model. The technique of applying the wave height contour map on deep water wave height vs. water depth plain is newly introduced. Integration of modified Rayleigh distribution multiplied with the normal distribution, which introduces the effect of mean water depth change in the model, over the equal wave height area on the contour map gives a probability distribution of wave height on slopes very simply.

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Strong interaction between a solitary wave and a submerged rectangular dike is studied, using the numerical solutions of BIM for fully nonlinear irrotational free surface flows in two-dimensional domain. The interaction takes a variety of deformations including forward or backward breaker, depending on the parameter ξ'_s which means the rate of the depth change due to the dike to the incident wave-height.
Some regression equations are derived from the simulation results and found to govern i) the critical incident wave-height for the occurrence of the wave breaking caused by the dike, ii) the location of the onset of the breaking and iii) the breaking wave-height at the location.

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The purpose of this study is to make clear the nonlinear effects accompanying resonant interactions on the wave height distribution of unidirectional irregular waves having arbitray spectral bands width and finite wave heights. The hydrodynamic equations of two-dimensionally irrotaional flow are solved numerically but very accruately, and then numerical simulations describing the long-time evolutions of the waves are carried out. Based on the simulated results, the nonlinear effects on the wave height statistics are investigated. As a result, it is found that the wave height distribution strongly suffers from the influence of nonlinear interactions higher than the 3rd order and changes its form in the propagation process. Further, a regression equation is derived to estimate the wave height distrigution of the waves suffering from the nonlinear effects.

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The cake filtration theory of the cross-flow ultrafiltration was discussed in this paper. The flux of kaoline suspension under coagulation was investigated and the improvement effect of permeability flux under coagulation and backwashing was estimated using the cake filtration theory. The property of the coagulated flocs changes because of the circulation of the concentrated suspension. Although the floc density becomes large under high mixing intensity of circulation, the sedimentation efficiency of the floc separation changes according to ALT ratio. The permeability flux is improved by the addition of Alum. The effect of coagulation especially appears over the ALT ratio range, 0.01 and this Alum dosage is coincided with the optimum dosage of Jar test. Although the filtration rate R_f of kaoline suspension (ALT=0) without Alum and backwashing is 1.4m/d, R_f with backwashing of 10 minutes interval becomes 2.3m/d. This R_f value is equal to the R_f value of the coagulation condition of ALT=0.05 without backwashing.

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In this paper the fuzzy linear programming model considering multipurpose is proposed for the municipal waste collection and transportation planning. This model gives the transportation routes and also the design waste amount of each area, considering the conflicting purposes (economy and safety), and taking the uncertainty of future waste amount of each area into fuzziness. The economic efficiency is evaluated to minimize the total transportation cost, and the safety to minimize the total risk of remained waste amount of the whole area. The sensitive analysis and the case study show that this model can help to decide the transport system of municipal waste, giving results that are a good balance of the two purposes. Furthermore, this model is available for the regional waste treatment and disposal planning.

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This research aims to evaluate the uncertainty in field permeability test and its corresponding generation structure, from hydraulic and stochastic point of view. It is assumed that the randomness in the test results is caused by the heterogeneity of hydraulic properties in the aquifer. By considering the spatial distribution of the actual permeability as a stationary random field, the variance of permeability value tested is theoretically formulated in terms of the head variance under a steady pumping condition. This paper shows that the accuracy of the steady pumping test is extremely improved when the observation well is located far from the pumping well. This is because the variance of head at the observation well reduces rapidly.

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