A real-time stage prediction system which takes account of backwater effect is developed. The system is made up of a real-time runoff prediction system and a flood routing system. The real-time runoff prediction system is used to forecast the discharge which flows into the upstream end of a channel reach. This system is based on the filtering and prediction theory developed by Kalman and others. A lumped runoff model is transformed into a stochastic model by incorporating noise terms. The resulting stochastic differential equations are solved by an iterative difference method with the aid of a statistical linearization technique. In the flood routing system, the flow of the channel reach is modeled using the one-dimensional equations of unsteady flow and these equations are solved with the four-point implicit method. The upstream boundary condition is given by the predicted discharge and the downstream boundary condition is given by the stage-discharge relationship as provided by the rating curve. As a case study, this system is applied to the prediction of the stages at the sluice ways located along the Ueno Retarding Basins.

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The objective of this work is to evaluate a mathematical model of heat and mass transfer through a sand layer under constant meteorological conditions. The mathematical models of evaporation in sand under the temperature gradient are compared with experimental results of temperature profile, vapor pressure profile and evaporation flux density. The computed results agree with the experimental results for all tests.
It is found that if arbitrary meteorological conditions and moisture content profile are given, the only set of evaporation flux density and temperature profile can be decided in the thermodynamically equilibrium condition.

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In-situ tests for measuring unsaturated permeability of shirasu are carried out by means of two methods. The first is the method that measures the variation of infiltration rates from the doublering infiltrometer. The other is one that does the variation of water depth in the recharging holes. Unsteady infiltration in the tests are numerically simulated to identify the parameters of Mualem's equation. The parameters are also identified from the laboratory test values that measured from the undisturbed soil. These results are compared and confirmed to be coincide with each other. However, evident difference is revealed in the numerical simulation; i.e. the computation for the recharging hole needs great amount of running time. From the results, it is cleared that infiltration test with infiltrometer is easy handling and useful method for the measurement in many locations.

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The authors proposed a new method for calculating the orographicaly induced wind field. Several methods to calculate the general wind field in mountainous area have been compared. We adopted as the model for comparison, Kao model, MASCON model, potential flow model and the modified potential flow model including Coriolis effects, which has been newly proposed by the present authors. Using these four models, the characteristics of wind field numerically calculated for a isolated mountain as a simple case of topography were investigated, and it was confirmed that only the modified potential flow (Ekman-Potential flow) model can explain the existence of strong ascending wind at the right of a mountain, which has been often observed by radars. The effects of complex topography on wind field were verified, and it was found that the Fourier components with wave length shorter than about 5km of the topography has not significant influence to wind field. By comparison of the results calculated using Ekman-potential flow model with the observation results using VAD method, it is confirmed that Ekman-potential flow model can represent actual wind field very well.

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Through field observations and hydraulic experiments we have revealed the mechanism by which common reed and ditch reed growing along river banks reduce bank erosion by mitigating erosive forces acting on natural banks of, for instance, flood flow and waves produced by boats. We also theoretically assessed critical velocities at which bank-protecting functions of reed can be brought out, the engineering validity of the theoretical approach were proved in field investigation.

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The conditions of the self-excited vibration observed in long span shell roller gate can be determined by both the model test and the field test. This self-excited vibrations have been observed under the small gate opening and both in the free flow conditions and slightly in the submerged flow at the model test. And this vibration have been observed also in the submerged flow in the field test. The condition for self-excited vibration occurs can be determined as the maximum discharge condition to take into account the deflection of the gate beam. By this condition, the zone of self-excited vibration can be determind at the designing stage by consultant engineers. After the theoretical analysis has been done by the unstable problem for the vibration of bending beam by takeing account the maximum discharge condition, this vibration is defined as the coupled vibration of two directions such as vertical and horizontal direction. So this is so called Flatter type vibration. And the measures to aboid the self-excited vibration can be offerd from this analysis.

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The boundary mixing coefficient of the shear stress which atcs on an interface between river flow and vegetation near river bank is determined analytically by applying 2 D-flow computational model. In this analysis, depth averaged currents are separated into main flow and deviated flow whose components can represent flow field with large eddies. It becomes clear that the values of boundary mixing coefficient evaluated from this analysis agrees with the experimantal values measured by FUKUOKA and FUJITA. Mechanism determining the boundary shear stress are examined in detail.

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The hydraulic transient with the propagation of an interface between open channel free surface flow and pressurized pipe flow is investigated numerically. The fundamental numerical simulation model is firstly described by means of the control volume method. Then, the simulation model is applied to the intrusion process of an air cavity into a horizontal duct, which was studied theoretically by Benjamin. The calculation is carried out under the hydraulic conditions of laboratory tests. It is pointed out through the comparison between the calculated results and the laboratory tests that the effects of vertical accerelation for the pressure distribution should be included in the momentum equation of open channel flow to reproduce the free surface profile near an moving interface and the following undular bore.

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In fluvial stream with vegetation zone along side wall, low frequency fluctuation of transverse velocity brings alternate lateral bed-load transport. Since the bed shear stress near vegetation zone changes rapidly in the transverse direction, net lateral bed-load remain after the average of one period of fluctuation. It causes longitudinal sand ridge formation; furthermore it accompanies a longitudinal sorting in case of graded materials. In this paper, flume experiment is conducted to demonstrate the above phenomena, and they are explained by using of the model of non-equilibrium bed-load transport.

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Runup of irregular waves on beaches has been studied on the basis of field and laboratory data. The long-period waves called infragravity waves predominate in an inner surf zone, when the slope of a sea bottom is gentler than about 1/20. They result in long-period runup waves on a beach. In the present paper, the breakpoint-forced long wave generation theory by Symonds et al. is modified so that the height of long-period waves can be calculated reasonably at the shoreline. Empirical formulae to estimate the height and period of long-period runup waves are also proposed for given conditions of the sea bottom slope and deep-sea waves.

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This study is intended to establish the estimation method of the stable weight of armor units of a submerged breakwater with wide crown, based on wave force characteristics. The wave force acting on armor units is, first, investigated and it is shown that it attains maximum around offshore-ward crown edge. Then, the theoretical model of the stable weight is derived by considering the mechanism of motion of armor units. Based on these results, this paper presents the stable weight diagram of the armor unit taking the acting wave force into consideration. In addition, it is revealed that the stable weight can be decreased with the increment of the distance from the crown edge.

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A numerical model is developed to predict the flow characteristics in a swash zone for obliquely incident wave trains. The two-dimensional shallow water equations are de-coupled into independent equations each for on-off shore motion and for longshore motion. A front of swash wave train is treated as a moving boundary to predict the motion for landward region of the still water shoreline. The results show non-vanishing longshore velocities and volume flux at the still water shoreline. These quantities are found to increase with the beach slope and incident wave period. The two-dimensional uprush and downrush motion near the front are found to be skew symmetric both in direction and in magnitude which may cause zig-zag longshore sediment transport inherent in swash zone.

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The results obtained from this study were summarized as follows; (1) The granulation mechanism of this process included three steps, i. e., small granule of about 100μm diameter were created at first, then they stuck together to increase in size, and finally granule of about 2mm diameter were formed; (2) The removal rates of TOC and T-N were nearly 97% and 70% respectively; (3) It was confirmed that, the Start Up of this process was longer than that of normal UASB process, but it could be significantly shortened by inoculating seeding sludge.

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Single high-loaded denitrification reactor has been developed and applied to treatment of night soil. Degradation of organic compounds, nitrification and denitrification occur concurrently in the reactor by the creation of both aerobic and anoxic zones and circulation of mixed liquor. In this study, a mathematical model is developed, in which the reactor consists of 3 zones (2 are aerobic and 1 is anoxic) and degradation of organics, nitrification, denitrification and growth of bacteria associated with each process are incorporated. The model is verified by the comparison of the simulated results with the tracer experiment and the performance results of the reactor operated in practice to treat night soil. The optimum operational conditions of the reactor for night soil treatment is discussed by the model. It is shown that the hydraulic retention time of 4.5 days in the reactor and DO concentration of 1mg/l in the middle zone between anoxic zone and higher DO zone are optimum for both fine and stable treatment.

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Biological nitrification can be inhibited by free NH₃ in wastewater containing high concentrated ammonium. Bio-zeolite reactor is developed in this study. It is a combined physical and biological reactor, in which zeolite is used as both adsorbent of ammonia and attached growth medium for nitrifier. In this reactor, concentration of ammonium nitrogen is kept by ion-exchange under the threshold level which causes the inhibition, and the ammonium nitrogen is nitrified by bacteria grown on the medium (zeolite). It is experimentally shown that ion-exchange and biological nitrification mechanisms occur concurrently, and that adsorption of ammonium nitrogen prevails when its load is larger than the nitrification activity. However, adsorbed ammonium nitrogen is released and nitrified after sufficient growth of nitrifier on the medium, then ion-exchanging capacity of zeolite is regenerated. Thus, stable removal of high concentrated ammonium nitrogen can be obtained, and successful response to stepwise shock loading is also shown without any serious increase of concentration of ammonium nitrogen. Ammonium-nitrogen loading per unit weight of zeolite is shown to be an important design parameter of this reactor, and more than 90% removal of ammonium nitrogen can be accomplished until the loading is increased to 0.15mgN/(g-zeolite·h).

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Recently, a vacuum extraction method is expected as the recovery method for the polluted groundwater by chlorinated hydrocarbons (CHC). In order to make an effective in situ remediation, it is indispensable to understand the mechanism of transport of CHC by the gas diffusion and the volatilization as well as the transport through water phase in the unsaturated and saturated zones. At first, in the present paper, the one dimensional column experiment and the numerical simulation have been carried out to evaluate the CHC transport in the unsaturated zone and the volatilization-dissolution rate between water and gas phases. Secondly, the CHC transport has been simulated for the infiltration of CHC from the natural river bed to groundwater by the two dimensional numerical model taking account for the gas diffusion. As a results, it was found that the gas diffusion and the volatilization influenced the CHC concentration in the unsaturated zone more than that without the gas diffusion.

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The purpose of this study is to estimate the influence of development activity on river ecosystems, especially as regards to fish. Fish preference was formulated based on experiments using shiner. A new formula was introduced with two strong points: First it is not required to change the values of the preference parameters when a new factor that influences fish behavior is introduced. Second, parameter values for the preference equation and weight values for the factors can be decided separately. By using this formula in a Shallow Sea Ecological Model (SSEM), shiner behavior in a model river was successfully simulated.

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By taking Hakata Bay as the example, and on the basis of the accumulated data on the water quality and the secular change of in flow load, it was pointed out that there is the nonlinearity between the inflow load and the water quality. Further, as the practical models, the improvement of the ΔCOD model taking the nonlinearity of internal production in consideration and the mass circulation model was carried out. Besides, as the simple forecasting technique for the water quality in eutrophic water areas, the simple conversion method by developing and expanding die concept of ΔCOD method was newly proposed, and it was shown that this model is useful as the purpose needs it, for example the case of evaluating the water quality on yearly average and so on. Moreover, by using these models, examination was carried out on the water quality control for eutrophic sea areas.

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A large amount of driftwoods flow into a dam reservoir during heavy rain or typhoon. These driftwoods are not only troublesome for the hydroelectric power generation, but it can cause the secondary disaster in a flood by obstructing the river flow. For this reason, it is one of the important tasks in dam maintenance to salvage these driftwoods whenever necessary. Salvaging driftwoods is very costly, and it is even more embarrassing to find the way of disposing them by burning or landfill. Now, based on the recognition that “the best way of driftwoods is to convert them into a usefulresources”, the research of turning these driftwoods into charcoal has been embarked because of the specifie characteristics of driftwoods in reservoirs. An experimental kiln of traditional clay type has been constructed, the carbonization methods, carbonizations on driftwoods and its properties have been investigated. It has also been attemped to extract organic compounds solution in the process of carbonizing the driftwoods. The charcoal and the organic solution obtained from driftwoods were proved to have sufficient commercial value based on chemical analyses and physical tests.

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Field observations were conducted at Ara-river in 1993 summer to evaluate the effect of heat balance on water temperature. The observation in the river course consists of measurements on long-and short-wave radiations, heat and vapor fluxes at water surface and measurements on vertical distribution of water temperature, saline concentration and transmissivity of solar radiation through the water body. The development of thermocline in the water body associated with net radiation was observed. It was found that the short-wave solar radiation dominates the balance of radiation, and it was also found that the heat convectively transported by flowing water is much larger than the heat generated by the radiation.

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How a zero-mean-flow turbulence decays after a turbulence-producing source was removed has been investigated numerically by using the κ-ε turbulence model. It has been also found theoretically that characteristic quantities of the turbulence decay in proportion to powers of the time elapsed from the stoppage of the energy supply. A time series of turbulent energy has been obtained experimentally in a decaying turbulence originally generated by the grid oscillation. The theoretical solution for the decay of turbulent energy agrees well with the experimental results.

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