Amount of water inflow into a dam reservoir is estimated from the increment of hydrostatic water level in the constant time intervals. The data of water inflow is important for efficient dam operation. Therefore, the measurement of hydrostatic water level with high accuracy is important work to know the exact amount of water inflow. However, the data of water level is disturbed by the signals of wind wave, seiche and so on. The estimation method of hydrostatic water level is demanded from a dam administrator. This paper proposes the new estimation method of hydrostatic water level using IIR digital filter, and the effect of this filter is discussed. It is confirmed that the water inflow can be estimated using the new method. And the accuracy of estimation is discussed by investigating the variance of filter output.

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Construction of tunnels and caverns affects not only groundwater flow and groundwater table over a wide area but also runoff in some cases. Changes in groundwater and runoff conditions during and after such construction should, therefore, ideally be estimated simultaneously by a hydraulic model that can reflect wide area topography and geology. In this study, methods for estimating surface discharge after the construction of tunnels was proposed, and the capacity of conventional quasi three-dimensional groundwater flow analysis methods was enhanced so that calculation of groundwater inflow into caverns due to changes in groundwater level could also be made possible. The proposed method was applied to the granite bedrock around an actual reservoir, and it could accurately evaluate the groundwater and surface discharge conditions during rainfall over a wide area. Applicability of the method to the study of groundwater inflow in caverns and surface discharge was confirmed by numerical simulation.

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Turbulent shear flow in a corner formed by a solid wall and a free surface is investigated using many flow visualization techniques and DPTV which combines Dye steak injection with Particle Tracking Velocimetry. The “wall streamwise vortices” are formed on the side wall and then developed to a free surface. And the vortices are moving away from the wall at the free surface. The vortices induce the secondary flow to the side wall and to the fine surface. Parts of the vortices tube agree with streaks on a free surface. The vortices form the boils on the fee surface.

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Turbulence measurements in open-channel flows with adverse-pressure gradients were conducted by making use of a laser Doppler anemometer(LDA). Hydrogen-Bubble technique was also used to measure the spanwise spacing scales of the bursting phenomenon. It was found that the bursting period normalized by the outer variables decreases with an increase of the adverse pressure gradient and also that the spanwise spacing scales normalized by the inner variables decreases with an increase of it. The contribution rates of the sweep event increases in comparison with those of the ejection event at near half depth.

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Instantaneous flow fields in open-channel flows with a horizontal dead zone, in which the aspect ratio (=streamwise length/spanwise length of the dead zone, i. e., L/B_w) is changed to 3, 5 and 10, were measured by making use of PIV (Particle Image Velocimetry). In the case of the aspect ratio of 3, the horizontal vortex exists stably. In contrast, in the case of the aspect ratio of 5, the vortices which are generated by the shear instability, i. e., Kelvin-Helmholtz instability, become larger in the downstream direction. In the case of the aspect ratio of 10, the reattachment phenomenon can be seen. The space-time correlation of the spanwise turbulence components decreases with an increase of the aspect ratio L/B_w.

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The fine component greatly influences the flow characteristics in the viscous debris flow occurred in the China. In this study, the debris flow composed of coarse particles and sluny (water and clay) was generated in laboratory experiments. It is found that the front of debris flow flows intermlittently by the jamming of sediment particles and subsequent failure and remobilization of the jammed particle even in the case that the viscosity of interstitial liquid is 80 times larger than that of water. The viscosity of interstitial liquid decreases the percolation through accumulated layer in the flowing stage. As the results, the transportation capacity of coarse particles decreases and the flow depth decreases.

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Formative process and domain of a self-formed stream in a straight river channel are studied by means of flume tests and numerical analyses. The results suggest that a self-formed stream can be produced on the conditions of steady water- and sediment-discharges and flat initial bed, and that it is produced easily in the generative domain of so-called multiple bars. In developing stage of a self-formed stream channel, multiple bars are produced firstly, and then transformed into alternate bars. Furthermore, the possible existence of multiple bars approaching an equilibrium stage is investigated by means of numerical analysis under a wide range of hydraulic condition. The numerical results suggest that any multiple bar changes into a self-formed stream under the studied conditions.

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In order to prepare the guide for designing rich-in-nature type of bank protection, we examined the stability of dry-laid masonry type of revetments in river bends experimentally, and investigated the flow action on the outer bank of bend using 2D numerical simulation model. It is shown that the index v_toe/v_avg (v_toe the maximum depth-averaged velocity over the toe of the outer bank, v_avg: the average velocity in the approach channel) is useful for evaluation of exerting force on bank, and that some kinds of parameters such as r/B (r: the radius of curvature, B: the width of river), dimensionless shear stress in the approach channel τ_*0, Froude number F_r, etc. have an influence on the value of index v_toe/v_avg. Finally, based on the above, we propose a method of evaluating the exerting force on bank.

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It is demonstrated theoretically that the characteristic wave u-c of shallow water equations is splitted into two waves on the erodible bed with the bed deformation. Such behaviors of the waves eliminate the flow analysis problem at Fr=1. The results of the theory are applied to the three types of numerical calculations using FDS method. 1. Rigorous calculations of the bed deformation; For Fr<1, main bed wave propagates downstream and reverse for Fr>1. 2. Flow calculation without bed deformation; Flow including the point Fr=1 is calculated successfully without any adjustment of the control section problem. 3. Simplyfied version of the bed analysis; The traditional way is modified in which the efficiency of calculation is more compared to the rigourous method.

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The long-term bar behavior was investigated with beach profile data obtained nearly daily for eight years at the Hasaki Coast, Japan. The position of the bar crest repeatedly moved seaward with a return period of a year. The cross-shore sediment transport, on the other hand, periodically fluctuated seaward and shoreward during the seaward migration of the bar crest. The relationship between the cross-shore sediment movement due to the bar crest migration and the wave energy flux in deep water was also investigated.

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A field measurement was conducted on Banzu intertidal sand-flat in Tokyo Bay, Japan, for 16 days in February 2000, aimed at investigating hydrodynamics, sediment suspension and short-term morphodynamic responses on the flat. The results of a 16-day measurement and a 6-year survey of bed levels have demonstrated that the Banzu flat has a morphological process consisting of a long-term gradual accretion, short-term episodic erosions and the following accumulations. The topography of the tidal flat fluctuated by approximately 8cm during the 16 days with the significant wave height in excess of 0.8m, which was relatively large for shallow waters in Tokyo Bay, although the long-term accumulation rate is estimated to be only about 3.8cm/y. Episodic erosions appeared to occur with high turbidity, which was caused by the combination of relatively high wave and strong tidal current accelerated by the wind between the high water and the mean water during the ebb tide. The tide fluctuation, as well as wave action and wind forcing, plays a key role in hydrodynamics and associated morphological process on the tidal flat.

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A dynamic model associated with water depth has been developed to simulate the growth dynamics of Phragmites australis. The biomass of shoots and rhizomes are analyzed with respect to various water depth. Phragmites australis have to grow over the critical height beyond the water depth while early season growing by stored material of rhizomes. There exists a severely influenced zone that aboveground and underground biomasses are sharply decreased as the water depth increases over the critical height. The severely influenced zone is varied with respect to initial rhizomes biomass. The density ratio per one shoot is decreased as the water depth increases, and the strength is also decreased. Morphological change of rhizomes contributes so as not to decrease the biomass under the critical height

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Periphyton population dynamic model was designed by considering growth patterns of the speicies and detachment effect of shear stress on their communities. The modell allowed us to simulate the vertical disparities of biomass, nutrients within the periphyton mat, and morphological competition between filamentous and non-filamentous algae. The validity of the model was confirmed by comparing the computed algal biomass of three algal species, Spirogyra, Achnantes minitissima, and Synedra with the experimental data. It was found that high nutrient concentration in the overlying water does not always stimulate periphyton accumulation, that overlying velocity and light condition mainly drove net growth rate and peak biomasses, and that decomposition of detritus contributed to a balance of nutrient resource in basal layer.

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Estimation and observation of SST by NOAA/AVHRR were carried out in the Ariake-kai bay and the Shimabara bay that are located in the west of Kyushu island to understand the heat movement. Local coefficients of estimation equation (MCSST) for SST in the Ariake-kai bay were calculated. The Fourier analysis of SST from NOAA/AVHRR was done to obtain the spatial distribution of annual variation of SST. Results show meteorological and geographical effects on heat environment of shallow and closed bay. A calculation of heat exchange using heat balance model gave us the results. which express the interesting movement of heat.

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Results of field and aerial photograph surveys are described on the behavior of backshore dunes during the period from 1984 to 1999 at three coasts facing the Kashima Sea, Japan. Data obtained through the field survey shows that the change in backshore height has positive correlation with the ground covering ratio due to vegetation. The aerial photograph survey shows that continuous longshore dunes are split into small dunes roughly 100m in length during a period of around 10 years, and backshore sands are blown into land-side coastal forest through gaps between small dunes. As found from both the surveys, total sand volume around the dunes in the Tsuno-ore area gradually decreased until 1987. However, it remained unchanged since then, as the shoreline was stabilized.

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This paper proposes a new approach using the Equivalent Frequency Response Method (EFRM) for analyzing St. Venant model for unsteady one-dimensional flow along with its related models such as kinematic wave, diffusion wave and gravity wave models with two different lower stream boundary conditions. It is possible to calculate the gain, time lag, and impulse response function by the proposed method. Moreover, a new criterion is presented for evaluating the validity of each model for a range of Froude and kinematic wave number based on the obtained impulse response function. Finally, this paper suggests the possibility of applications of EFRM to real runoff analysis.

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Formation process of gully-headcut has been simulated through numerical methods. 2-D depth-averaged flow model with non-orthogonal boundary fitted grid system is employed to describe discharge distribution around gully-headcut. The heterogeneity of unit discharge along headcut promotes gully development process. Simulated result shows initial shape of the gully-headcut is very important for its further development and advancement. Headcut convex shape from up-stream side is a necessary condition to develop gully, while the concave shape is disadvantageous in gully development process. Higher convexity, especially around gully-head, makes the gully development process faster.

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In this study, a model for computing water temperature in the Lake Yanaka is established. The main feature of the model is the use of secchi disk depth to better estimate the heat budget. Secchi disk depth observation is incorporated with empirical relationship to calculate more accurately the solar radiation fraction coefficient and the extinction coefficient. Besides, the eddy diffusion coefficient, under the assumption of complete mixing, is calculated from the wind shear, density stratification, and inflow and outflow rate. Model results are compared with the observation data.

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