The encroachment and intrusion of the sea water wedge toward the underground caverns in coastal rock mass are investigated experimentally and theoretically. The theoretical analysis was done by using the boundary integral equation method. The experiments are conducted in the Hele-Shaw model with two different densities of fluids. Comparing theoretical results with experimental ones, the application technique of the boundary integral equation method for analyzing the fresh-sea water interface in coastal rock aquifer was confirmed. In addition, the process of sea water encroachment around caverns was made clear.

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The flood run-off form of medium and small rivers have been changing markedly with the improvement and expansion of public facilities such sewerage systems and roads. This paper describes the Urbanization Number, one of the urbanization indices which evaluate the relation between the progress of urbanization in the river basins in built-up areas and the change in the flood run-off form. The Urbanization Number is expressed by a linear model composed of percent impervious area, percent river improvement, percent sewerage improvement, etc. It is characterized in that it can quantify the degree of influence of the improvement of sewerage systems and rivers on the flood run-off form.
Moreover, the use of this Urbanization Number permits to easily estimate the run-off coefficient and effective rainfall in the national formula relating to the run-off characteristic of medium and small rivers in urban areas.

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Similarity of horizontal diffusion in hydraulic models is generally difficult to achieve because the diffusion law is often not known and small scale ratio is often used. It is generally accepted that use of roughness elements is necessary to generate turbulence in the small-scale hydraulic models. Quantitative assessment of such roughness elements, e. g. roughness bars or strips, with regard to the horizontal diffusion, however, has not been studied extensively. In this paper, a flume study is carried out to obtain the velocity defect law in the presence of roughness bars. Based on the obtained velocity defect law, the horizontal turbulent diffusivity is derived using the Prandtl's concept of mixing length and the Reynolds' analogy. Experimentally verified law of horizontal diffusivity thus is expressed in terms of flow velocity, radius of the bar elements and spacings of roughness bars in two horizontal directions.

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Unconfined groundwater behavior is generally complex in time and space due to variety of hydrogeological properties in the flow region. It is necessary for the simulation analysis to characterize the uncertainty about the head field and to evaluate the accuracy of observed hydraulic head. In the present paper, assuming statistical homogeneity, the variogram which expresses a spatial structure of the head field was derived analytically from the physical laws. This theoretical variogram was consistent with the variogram that was calculated using observed data. The head fields after a rainfall were stochastically estimated by using the Kriging method and theoretical variogram. It has been clarified from the result that an extent of the role of observed data for the estimation of the head field becomes gradually important more and more through a long-term recession process.

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In the flow over a rippled bed, there exists a systematic eddy motion over the crest or from the reattachment point etc., and so the turbulence structure is very complicated. Since the suspended-load in such a field is affected considerably by such an eddy motion, the characteristics of the suspended-load distribution are more complicated than that in a flow over a flat-bed and vary throughout the wave length. In this paper the simultanious measurement of the concentration and two components of the water velocity was made and both characteristics of the water flow and the suspended-load were quantitatively estimated. As a result, the mechanism of the suspended-load, particulary the effect of a systematic eddy motion on the suspended-load is revealed and it is found that only near the crest, the concentration distribution can be approximately estimated by the equation proposed by authors in the case of the equilibrium condidtion.

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Longitudinal and lateral transport rates of uniform sediment and heterogeneous mixtures are measured experimentally with a laterally inclinable wind tunnel, and the sediment transport rates are formulated in terms of Shields stress, critical Shields stress and lateral inclination angle. The critical Shields stress of uniform and heterogeneous materials in air flow are observed to be much smaller than those in water flow. The critical shear velocity for each fraction size of heterogeneous mixtures does not depend on the size, which indicates that the incipient motion of sediment in air flow is the impact threshold. The amount of sediment transport in air flow increases at very large rate against Shields stress in the vicinity of the critical Shields stress. The ratio of lateral sediment transport to longitudinal one for heterogeneous mixtures is found to depend on the sediment size, because larger sizes feel the lateral gravitational force more than the finer ones.

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This paper presents a finite element method for the analysis of linear water wave problems using the mesh optimization technique. The numerical model is based on the mild-slope equation. The hybrid element method is employed for the numerical treatment of the open boundary. The key feature of this method is that the approximation error based on the finite element discretization is estimated and the finite element mesh is redivided to minimize the total amount of the error. This follows that the accuracy of the numerical solutions is improved automatically. The numerical solutions obtained are compared with analytical solutions. The present method is shown to be an useful and effective method for the analysis of linear water wave problems.

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Numerical calculation techniques of turbulent shear flows are classified into two categories: one is κ-ε turbulence model and the other is large eddy simulation (LES). The standard κ-ε model has been established at present to predict turbulent structure in closed duct flows, while LES is being developed to predict coherent eddy structure in more simple duct flows. The standard κ-ε model cannot be, however, applied to open channel surface flows, because the turbulence near the free surface is more depressed than the closed duct flows.
In the present study a new modified κ-ε model is proposed to predict reasonably the turbulent structure in open channel flows with both of low and high Reynolds numbers. The numerical calculations indicate a splendid agreement with the experimental data which were obtained by making use of hot-film and Laser Doppler anemometers.

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A temperature gradient-type micro flowmeter has been devised to measure water particle velocity less than 1cm/s appearing in the flow condition in the tidal current field. The fundamental characters and applicability of the flowmeter for the flow condition mentioned above has been discussed theoretically and experimentally, especially on the problem such as its sensitivity, response character and calibration. Through the present paper, although there remains the difficulty due to the nonlinear response of the flowmeter to time variation of the velocity, it turned out that the flowmeter can be applied to measure the very low velocity. The flowmeter devised here can give us a useful tool to discuss the such problem as the hydraulic mechanism of the tidal and residual current fields.

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Based on systematic field observations of trichloroetylene (TCE) concentration at 27 wells in Taishi Town, Hyogo Prefecture during the period from January 1984 to August 1985, convection and dispersion processes of the groundwater contamination by toxic organic chemicals are examined hydraulically. Variations in the TCE-concentration are shown to be classified into two characteristic patterns; monotonically decreasing one with time and cyclically changing one with the seasonal variation. Calculations of groundwater flows by using simple potential theories show that the observed variations in TCE-concentration might be dependent of the variations in the surface level of unconfined groundwater. Furthermore, the convection velocity of TCE-concentration is found to be small as to be 5×10m/day in summer and 10⁰m/day in winter, which approximately agrees with field observation results.

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The effect of periodic two-dimensional excitation on the development of a turbulent mixing region in open-channel parallel coflows was investigated experimentally by making use of visual study and hot-film anemometers. Controlled oscillations of variable frequency were applied at the initiation of mixing between two parallel water flows. When the frequency of the forced oscillations was lower than the fundamental frequency (in the present case it was about 1Hz) which might describe the interaction of vortices, i. e. pairing, the spreading rate of flow was increased by enhancing the coalescence of neighbouring eddies. On the other hand, at the frequency higher than the fundamental one, the controlled and resonant vortices were generated in a single array of large vortices, which did not interact with each other. Consequently, the spreading rate of flow was depressed, and also the Reynolds stress became negative.

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This paper presents the reduction effect by entrained air to scour from plunging jet on the basis of the experiments and the numerical analysis. The experiments of scour were carried out under a shallower tailwater depth than the penetration depth of airbubbles which is observed under a fully deep tailwater. The characteristics values of scour profile, such as the maximum scour depth and the height of the ridge and so on, were compared with those in the case of the submerged impinging jet. On the other hand, equilibrium maximum scour depth for the asymptotic steady state are calculated by making use of the numerical analysis model. The calculated results agree well with the experimental results. And the reduction effect by entrained air is shown by the equations arranged the calculated results.

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In this paper, the simple method for the hydraulic analysis of the high velocity flows through curved open channels is shown with some numerical results which contain the longitudinal and transverse distributions of hydraulic variables. It is shown that the fundamental equations used here are equivalent to the previous studies by von Kármán and Lenau mathematically. The numerical results are divided into three groups qualitatively and compared with the analysis of von Kármán and Lenau. When R/B becomes lager, the numerical results will gradually approach to Lenau's solutions. It is also shown that the effects of the bottom shear stresses can be considered by extending the method used here.

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River mouth process is investigated at the Abukuma River. Firstly, topography change process with long time scales is discussed analyzing the maps since 1907 and the aerial photographs since 1947. Secondly, the short time scale process is reported basing on the field surveying since 1984, which includes the observations of floods on July 1, 1985 and August 5, 1986. It was concluded that the morphology is to be changed drastically by flood larger than 2500m³/s in case of the Abukuma River. The factors relating the process are also discussed in the paper.

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The main purpose of this study is to present and discuss the results of field observation and numerical simulation of deposition and resuspension of cohesive bottom sediment in a shallow lake. Field data taken in Lake Kasumigaura, such as lake current, wind over the lake, water wave, and turbidity of the lake, are shown. Based on these results, we discuss how sediments were suspended in this lake. We show the model to estimate the bottom shear stress causing sediment resuspension and the equations expressing the behavior of resuspended sediment in current which are used in the above simulation. The calculated turbidity showed a good agreement with that obtained by the field observation.

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Analytical solutions with respect to variation of river water levels in the tidal reach are presented for such boundary condition that the tidal oscillations of long period are given at a river mouth. The solutions are the approximate ones of the third order which are derived by a perturbation method and have the satisfactorily high accuracy compared with the ones of the second order. Based on those solutions, the relationships are theoretically investigated between the highest water levels along river channel and the hydraulic parameters, namely, amplitude and period of tidal oscillation at river mouth, river-bed solpe and river discharge. Highest water levels are also compared with water levels of the steady nonuniform flow when the water level at river mouth is kept constant at the peak level of tidal oscillation, in order to examine how safe it is to adopt the water level of nonuniform flow as the design high water level.

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The simulation of particle settlement in oscillating fluids, which motion is followed by the equation of motion derived by Tchen, is performed, and the results of simulation are verified by the experimental data obtained by Ho. It is revealed that the factors governing retardation of fall velocity are particle Reynolds number, Strouhal number and the ratio of the amplitude of flow oscillation to a particle diameter. Futhermore, when the suspended load in the channel flow is analysed by the simulation model, the criterion of the reasonable calculating time step is proposed based on the results of this study.

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A numerical method for precalculation of temperature and humidity distributions along air current in tunnel was established, in which sensible heat and material transfers from rock to air current related to non-steady heat conduction in rock around the tunnel are taken into consideration. Seasonal variations of surface climate were measured at the entrances of Abo tunnel where investigation tunnel is under excavation. The original temperatures and the thermal constants of rock along the tunnel were also investigated. And prediction calculation has been carried out, being based on the investigation results and assuming traffic conditions or the cases where sudden changes of surface climate happen.

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The purpose of this paper is to separate the total storm runoff into components by the following methods.
(1) The first method is to separate the total discharge, using bio-geochemical indicator (δ¹⁸O, NO^-₃) into overland flow, inflow and groundwater flow by the mass balance equations describing the fluxes of water and the tracers in the stream.
(2) The second methods are to separate the total runoff into each components by Filter separation AR method and Tank model.

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A stochastic typhoon model with three properties of central pressure, moving direction and moving velocity is constructed by using B-spline functions and multi-variate autoregressive models. This stochastic typhoon model generates hourly data of typhoon location, central pressure, moving direction and velocity. Predictors against the rainfall intensity and the storm surge at Osaka are selected by using a stepwise regression analysis. About 2820 typhoons for 600 years are generated, and rainfall intensities and storm surges associated with the simulated typhoons are generated at Osaka. The concurrent characteristics of rainfall and storm surge; such as the frequency distribution of time lags, the spatial distributions of typhoon locations, when the peak rainfall intensities and the maximum storm surges occurred. At the same time the joint return periods of heavy rainfall intensities and large storm surges, are evaluated by using observed and simulated data.

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It is important for evaluating water budget in river watersheds to develop more precise estimation of evapotranspiration. In this paper, a new method for estimation of daily actual evapotranspiration rate from forest watershed is proposed.
Being based on the observation data of daily evapotranspiration in a forest site, the Penman's method was extended to the cases having unsaturated ground conditions, and the parameters of the new method were determined by the observation data. The estimating calculation in the new method needs only conventional daily meteorological data.
The method was applied to various three experimental watersheds, and the annual evapotranspirations estimated by the method showed fairly good agreement with that by the water buget method in the watersheds.

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This paper presents a simple analytical model for predicting the transformation of a bore caused by the spilling breaker of a solitary wave over a horizontal bed. The basic equations used are the laws of mass and momentum conservation, in which the pressure terms are corrected to include the effects of a deviation from the hydrostatic pressure and a non-uniformity of the velocity distribution. The surface profile is evaluated on the assumption that the flow field of the bore is similar to that of a dam-break flow. The validity of the solutions is examined through comparison with the results of laboratory experiments. It is found that the present model is applicable to the bore transformation over a horizontal bed except for a short period after the formation of the bore.

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Characteristic equations are deduced for shallow water waves with velocity distribution due to bottom friction. It is shown that the effect of velocity distribution plays an important role at the wave front on dry bed. It changes the wave front path from the envelope locus of the characteristics to the nodal locus. Integration of the equations gives a bounded solution for certain range of the exponent α on the depth. The range varies depending on the singularity at the front. Hydraulic experiments have been carried out and velocity distributions are measured at the still water shoreline by the hydrogen bubble method. The time developement of the velocity distributions show a similarity.
Numerical analysis by using the characteristic equations and measured velocity distributions as a boundary condition shows a good agreement with the measured values of wave front path and spatial wave shapes.

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In this paper, an alongshore distribution of extremes of typhoon-generated waves around the Pacific coast of Western Japan is re-evaluated on the basis of a spectral wave prediction model for calculating shallow-water waves at a fixed location. First, the accuracy of the model is examined by comparing the computed and observed significant wave heights during many typhoons in recent years. Second, from wave hindcasting for 101 typhoons which attacked Japanese coasts in the past 50 years, alongshore distribution of maximum significant wave height and wave height for return period of 50 years is estimated and compared with the distribution of design wave height for coastal structures. The effects of the wave prediction model and mesh size used in the computations on maximum wave height are discussed by comparing the present results with the results previously estimated by the authors.

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A mathematical biofilm model was developed considering substrate decomposition and diffusion rates in a regime of consecutive reactions. By using the model, removal rates of propionate, butyrate and an acid mixture within anaerobic biofilms, as well as the rates of intermediate acetate, were analized to obtain biofilm parameters which specified treatment characteristics.
Variations of the biofilm parameters, i. e. dimensionless biofilm property (M_A, M_p, M_B) and operation parameter (Pe_A, Pe_p, Pe_B), were represented as a function of the attached biomass. By using these parameters, treatment characteristics of anaerobic biofilm reactors in the methane production phase were simply and accurately evaluated.

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A simplified equation for computing the backwater curve of steady flows in a wide rectangular channel is derived by using a perturbation method. The obtained formula is expressed in such a manner that water depth is given as a function of the distance from the downstream end, while most of the formulae previously proposed express the distance as a function of water depth. The results computed by the obtained formula are compared with those by the finite difference method, and it is proved that the formula has the satisfactorily high accuracy for practical computation of backwater curves. If neglecting the inertia term, or gradient of velocity head in the fundamental equation, the formula could be further simplified. But the omission of that term yields the large error of computation for such hydraulic condition that the ratio of normal water depth to critical water depth is less than about 2.

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Microbial aggrigate model discribed by double monod type and in which diffusion layer was taken into account was numerically analyzed by orthogonal collocation method. The model discribed by A. O. Lou et al. without diffusion layer was compared with our model with diffusion layer, in order to investigate effect of diffusion layer on the competitive growth of filamentous and floc former bacteria. It was reported that diffusion layer influenced the competitive growth in activated sludge floc.
The collocation number used in this study was ten, because the calculation of substrate removal flux converged at the collocation number.

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