Saltation motion of blown sand is analyzed by coupling of solving equation of motion and the model fore irregular repulsion on the bed surface. Furthermore, the suppression of the Reynolds stress due to the additional force by which the blown sand is accelerated is taken into account to evaluate the wind velocity distribution. Under equilibrium, by using the fact that the Reynolds stress at the bed should equal the critical tractive force, the equilibrium transport rate and wind velocity profile with blown sand are predicted reasonably.

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Mixing effects on sediment discharge of sand and gravel are discussed based on experiments with mixtures of sand and gravels with uniform grain size. Gravel discharge in mixtures becomes larger than that in uniform gravels when the volumetric percentage of gravels in mixtures is less than about 50%. This is caused by the reduction of repose angle of gravels on sand as well as their excess exposure to the flow. Sand discharge becomes generally smaller in mixtures, but when the gravel discharge increases largely with the mixing effect, sand discharge increases due to the effect of collision of gravel with sand.

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This paper describes a new formula for the calculation of the maximum rate of bed-load transport on smooth and fixed beds. The transport rate in unit width is expressed as the product of the volume of the moving particles on unit area of bed surface and their mean advancing velocity. Both the factors are formulated by considering, more strictly than previous studies, the inter-ference between fluid and moving particles, the variation in friction coefficient of the particles with their velocity and so on. The results of calculation with the proposed formula show fairly good agreement with existing flume data.

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As a result of measuring the rheological properties of mud using a rotational visco-meter, the mud can be considered as structural viscosity fluid. We formulate a rheological equation of mud based on these properties. A hydraulic model of mud-flow under the flowing water is constructed by introducing the rheological equation. Computation using this hydraulic model can replicates the features of the velocity distribution of mud-flow which are recognized in hydraulic experiments.

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Resistance of pipe flow with a stationary bed and with bed load on sediment deposition in pipes is discussed theoretically and experimentally, in which water flow area and hydraulic radius in a cross section of the pipe is divided into two parts: area and hydraulic radius influenced by smooth pipe wall and those by rough sediment wall. Experimental results about mean velocity and sediment transport rate in a pipe proved that the division of hydraulic radius of the water flow area into two is useful for the estimation of flow resistance and bed shear stress

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The flow resistance and bed-load discharge in a circular pipe with deposit bed is investigated by numerically analyzing with algebraic stress model of turbulence. The present calculation has clarified shearstress along the boundary including the surface of the deposit bed, which distributes transversely. By applying Swiss-formula for bedload transport, the local rate of bed-load transport is estimated, and then the total bed-load discharge is evaluated by integrating the local rate. The results were well consistent with the previous experimental data.

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Non-steady process of transversal sediment transport in a straight sandy rivers with bank vegetation was experimentally investigated. Location of sediment deposition in a vegetated zone was determined by vegetation density, and it spreads to faraway region from the interface between vegetated and nonvegetated zones with decrease in vegetation density and with time. Thus, deposition rate of suspended sediments in the farway region increases relatively with time. In addition, a concentration profile of suspended sediments also varies with time corresponding to change in sediment suspension and deposition.

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In fluvial stream with vegetated zone, lateral bed-load transport is induced by low-frequency fluctuation of transverse velocity and a longitudinal sand ridge is formed along the boundary of vegetation zone. In case of graded material, it accompanies a longitudinal sorting, and a longitudinal stripe is characteristic where is covered by fine materials. Flume experiment is conducted to demonstrate the above sorting process, and it is explained by using the non-equilibrium bedload transport model for each grain size

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This study aims to develop a renewal or conservation method of the riverbank with or without bank protection works. As the first step, a trench test was carried out at the natural riverbank of the Tone River, where the riverbank was formed by the installation of several spur dykes in the 1960s, in order to investigate formative process of the natural riverbank. It is concluded through this field investigation that formative process and the developing velocity of riverbank strongly depend on changes in the water and bank lebel, and the enhancement of depositional effect of fine sediments due to the growth of vegitation on the riverbank.

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The estimation of resistance to erosion of levee and natural riverbank is very important to enhance the safety of levee and natural riverbank against erosion. A new technique by open channel flume experiment with large and undisturbed test pieces is developed to measure critical velocity and rate of erosion. Further a tension test apparatus is newly developed to measure a tensile breaking stress of cohesive soil. The measured results indicate the tensile breaking stress is proportional to the square of critical velocity and well characterizes the erosion process.

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The method of excluding the deposited sediment by dropping water level and increasing the tractive force in dam-reservoir was discussed. But, when this method is applying into the diffusive theory of river-bed variation, it is not clear that which boundary condition must be used for different width of excluding gate and river. This study is concentrated on finding such a suitable boundary condition. experimently and theoreticaly. The comparison between the theoretical curve and the experimental data shows fairly good agreement.

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A particle tracking velocimetry (PTV) for 2-D space has been developed and proved efficient through its application to turbulent measurement in thermal convection. It consists of the Kalman's filtering theory to estimate location of each particle image in the next frame, and the Chai-Square-test to evaluate the probability that a particle image in the next frame is identical to the estimated one. An auxiliary technique utilizing a generation method of the Delaunay triangular network is also employed to set initial estimates of velocities of particles which newly appear in the frame. The technology is now under improvement to be applicable to flow measurement in 3-D space. Some other efficient techniques to support the PTV under development are also presented.

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Many turbulence measurements have been ever conducted by point measurement techniques such as hot-film anemometers (CTA) and laser Doppler anemometers (LDA). Compared with these techniques, coherent vortex phenomena are easily recognized by flow visualization techniques.
In this study, images of very small 100μm diameter particles uniformly scattered in compound open-channel flows were taken using a CCD camera and 2W Argon-ion laser slit illumination. These images were stored through frame memory board from an optic disc controlled by a personal computer. Instantaneous velocities at many points in the laser slit plane were measured from these continuous four images of one particle. This new method is called the “Particle -Image Velocimetry (PIV)”, and seems to be very powerful to investigate coherent vortices in space and time because simultaneous velocities at every point can be obtained.

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All the three velocity components in unsteady flow inside and near an embayment, which was made on the flood plain of a compound channel, have been measured with electromagnetic probes. Unsteady flows were simulated by three hydrographs in a 25m long, lm wide tilting flume. Shown here are the temporal variations of the depths, as well as the longitudinal velocity component's variations with time and water height. The circulating flow's evolution with time during a hydrograph is clearly demonstrated by the experimental results.

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Instantaneous three-dimensional velocity fields of separated flow in a sudden expanded open channel are obtained by using multi-section flow visualization and the Mass-Consistent model. The three-dimensional distributions of instantaneous velocity, vorticity and Reynolds stress are given at a short time interval and their characteristics are investigated. The instantaneous flow at downstream is highly three-dimensional and unsteady. The end-view of instantaneous velocity (v and w components) at x/B=6 shows a counterclockwise rotating field. The upper portion of the separated shear-layer does not reattach to the channel side wall and its spanwise oscillation is larger at x/B>4-5.

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A P. C.-controlled automatic measuring system is developed for quantifying three-dimensional structure of open channel flows. Manual-controlled measuring systems require a great deal of time and labor as well as cause error in measurements. The proposed system allows us to obtain the velocity field of the considering flow with little manpower and high accuracy. In addition, an error inherent to spacing of two sensors, which usually occurs in measurements of velocity components by X-type Hot-film anemometer, is rectified on the basis of logarithmic velocity profile.

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Field measurements of turbulence was carried out at a bend in an artificial channel by electro-magnetic anemometers. Dimensions of the channel are 4.8 m in height and 5.5m in width. The velocity in the channel exceeds 1 m/s. Number of the measurement points is 83 at a section. Since the velocity is fast and the flume is large, the special cares were taken for the measurements. The frequency response of the anemometers must be quick enough for the turbulence, and the directional characteristics must be accurate. Moreover, the supporting apparatus of the anemometers should not influence the flow and should not vibrate with less than 8 Hz. The problems above are carefully examined by laboratory experiments. As the results of the field measurement the asymmetric secondary flow cell were found, probably due to the difference of the roughness.

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Field measurements of three-dimensional turbulent structures were conducted in curving river streams at a point bar and an alternating bar. Clear secondary currents were observed in the curved sections, but they were transformed by shape effects of the cross section. The structures of mean velocity and turbulent quantities indicated characteristic properties according to the developing stage of flow due to the stream curvature. Evaluation methods of bed shear stress using the log-law, Reynolds stress and turbulence intensities were investigated.

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An image analysis method for the calculation of two-dimensional velocity distributions of river-surface flows is examined. In this method, complicated water surface configurations, which are created by the confliction of boils to the water-surface or by the fluctuation of pressure influenced by turbulence, are considered to be convected with the water surface velocity. Water surface images are taken from the riverside using a video camera. Velocity distributions are calculated by the correlation method after the transformation of images to the non-distorted ones. The application of the method to the Nagara River indicates favorable velocity distribution for the downstream components.

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The three-dimensional configurations of river bed were measured by a echo sounder, and, at almost the same time, time series of photographs were taken of the patterns of tracers scattered on the flow surface during a flood stage in the Hii River.
Photograph data were analyzed by picture processing technique to obtain velocity vectors. The relationships among streamlines, vorticity and divergence calculated from the obtained velocity vectors were examined.
The characteristics of wave height and wave length of dunes and small scale bars measured during the decreasing stage of flood flow are examined. The height of small scale bars increases while one of dunes decreases during the stage.

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Between June and August, 1993 field observations and measurements of debris flows have been carried out at two locations on Mount Unzendake. One of the instrumented study sites was a downstream reach of the Mizunashi River, which is11.6m wide and have an average slope of about 2.9°. The other was a downstream reach of the Nakao River, which is 7.2m wide and have an average slope of about 1.4°. Radio current-meter and ultrasonic water level gauge were used to obtain surface velocity, depth and discharge for the several flows.
The value of nondimensional surface velocity u_s/u_* was found 5. Peak discharge was found Q=195m³/s at the Mizunashi River and Q=40m³/s at the Nakao River. Spectra of velocity and water-level variance shows maximum at f≈10^-2Hz.

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A physically based model which predicts rainfall distribution using three-dimensionally scanning Doppler radar is proposed.
Most of short-range rainfall prediction models using three-dimensionally scanning radar are based on time-extrapolating method. Since physical processes of rainfall phenomenon are not included i those models, the accuracy of prediction is difficult to be more improved.
So we offer the method which takes into account the water balance and its phase change in the atomosphere as well as the wind components estimated by VAD analysis using three-dimensionally scanning Doppler radar. The results from a numerical experiment indicate that this method is more effective for short-range rainfall prediction than time-extrapolating method.

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This paper reports characteristics of synthetic aperture radar (SAR) imageries obtained by two new satellites: the European Remote Sensing Satellite (ERS-1) and the Japanese Earth Resources Satellite (JERS-1). The authors compare the SAR imageries in terms of distributions of the CCT values and the backscattering coefficients for several kinds of land cover in a watershed near Nagoya, Japan. The results of comparison show:(1) In a water area, the mean backscattering coefficient is about -15 (dB) with the use of the ERS-1 SAR data and JERS-1 also. The value is smaller than the backscattering coefficients in areas except the water area;(2) The backscattering coefficients in areas except the water area by the ERS-1 SAR data are larger than the ones by the JERS-1 SAR data;(3) To delineate a water area, it is better to use the ERS-1 SAR data than the JERS-1 SAR data; and (4) To identify boundaries clearly between various land covers except a water area is difficult by the use of ERS-1 SAR data and JERS-1 also.

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We converted a small commercial X-band radar into an instrument for measuring three dimensional distribution of rain drops and/or snow flakes in the air. In this paper, we present the results of a test on its ability of measuring snow flakes distribution. The radar echo clearly shows that crows of snow flakes are advected by wind, which pattern corresponds to the results of observation on the ground in good accuracy. A consideration is made to rectify the nonlnearity of echo attenuation in distance.

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Assessment of the vegetation activity is essential to assess ecological environment. It is characterized by Net Primary Productivity (NPP). The relationship between NPP and the time integral of Normalized Difference Vegetaion Index (iNDVI) is studied. At first, land use is classified into some categories from Digital National Land Information. The value of NPP is compared with iNDVI derived from NOAAAVHRR at each land use. Appling this method, distribution of NPP is derived in the eastern Japan.

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This paper discussed the method for indicating the spatial distribution of vegetation amount in a watershed by means of LAI (Leaf Area Index) from a TM image data of Landsat-5. First of all, the relationships between LAI and vegetation canopy spectra were investigated on the basis of the obtained experimental data. As a result, a high correlation between LAI and NDVI (Normalized Difference Vegetation Index) was found. Next, the LAI image of a study basin was obtaind from a TM image data of Landsat-5 on the basis of the relationship between LAI and NDVI. The LAI image made it possible to estimate the spatial distribution of vegetation amount in a watershed.

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The hydrological information at the large area are important to know the interaction between the land surface and the atmosphere. Now the microwave sensors mounted on satellites such as E ERS-1 and J ERS-1 are expected to collect the new information. This study will focus mainly on the relationship between the soil moisture and the backscattering coefficient measured by the microwave sensors. The backscattering coefficient value is affected not only by the soil moisture but also by other factors such as polarization, incident angle, sensor's frequency, surface roughness, soil composition etc.
This paper examines effects of polarization and incident angles on the backscattering for two different experimental sites, using a C-band scatterometer system. In case of the bare soil, as the incident angle increases, the backscattering coefficient value decreases. As for the relationship between the soil moisture and the backscattering coefficient, as the incident angle increases, the soil moisture sensitivity increases while the correlation coefficient decreases. In the measurement of the soil moisture by the C-band scatterometer at FIELD, the better system combination is found to be the cross-polarization and the incident angles at 20°.

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The horizontal two-dimensional ocean currents in the sea surface were observed using two HF radar in the sea off Fukushima from March to April in 1993. In the far field over 4km off the coasts, the velocities derived by the HF radars were in good agreement with the field data by a velocimeter. The current variability was investigated horizontally by the current vectors, the divergence, and the rotation estimated by the HF radar.

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In order to carry out effective countermeasures for water quality in dam-reservoirs, it is necessary to observe water quality in detail. MSS on aircraft is useful for observation of horizontal distribution of water quality. The observation by MSS which has 12 bands was carried out for 3 dam-reservoirs and the distributions of water temperature, SS and chlorophyll-a were analyzed by the relationship between CCT count of specific bands and ground truth data for each item. As one of the results, a sinking point of inflow which has high density was identified clearly.

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The pieces of dyed filter paper were exposed to rain, and both the size and position of the drops were determined. Lovejoy et al.(1990) reported that the spatial distribution for raindrops was fractal. Therefore this inhomogeneity of raindrops will lead to the correction for the standard theory in radar rainfall masurement. In this study, the fractal dimension of spaital distribution for raindrops are calculated, and are extended to the rainfall rate and the dropsize. This calculation gives the suggestion that the spatial distribution has the pink noise.

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The hydrologic measurements are always affected by various types of errors. Fuzzy number may be used to express the uncertainties in rainfall and discharge data. In this paper, Fuzzified neural network model is capable of learning the complex runoff process ongoing in a basin, and presented for the calculation of the sequences of river discharge using the inaccurate data. This model is a kind of black box deterministic models that consist of a highly interconnected network between fuzzified input and output, and no physical meanings. This model is expected to yield more accurate results than other deterministic models with less available hydrologic data.

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To consider the interaction between runoff process and meteorological one, a methodology to scale up a distributed runoff model is developed.
In our methodology, the stream network is regarded as a set of sub-networks devided by grids whose size is so large as to be compatible with meteorological scale. The model of flow within these sub-networks and its numerical solution algorithm are given.

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Recently, in order to improve the condition of rivers downstream of dams, the preservation discharge from a reservoir has been drained off for conservation of river environment. However, in a watershed basin where sedimentary materials are actively produced from a mountainous area, it is impossible to disregard the seepage flow from river channels, i. e. the river-bed flow, because a thick layer of sediment is formed on the bottom of a valley. The purpose of this research is to consider the hydraulic characteristics of the river-bed flow downstream of dams. Through the theoretical analysis based on the physical principles, the spatial distribution of seepage potential, the seepage rate and its total quantity from the channel have been evaluated. The analytical results have been validated by the numerical simulation combined the river-bed flow with the channel flow.

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Because the water stage is seasonally varied in a reservoir for flood control, there appears unsightly non-vegetated band along the margin, which diminishes the value of a reservoir, eg, for resort use. In this paper, some basic data are presented for vegetating the bands with S. Gilgiana which is persevering to submergence. Its growth rate under the condition of flood control reservoir is estimated by a field survey in Kamafusa reservoir. The result shows that the estimated growth rate is about the half of its value under an ordinary growth condition. A consideration is made by refering to the seasonal variation of the water stage and the characteristics of seasonal growth of S. Gilgian.

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A Reynolds stress equation model is developed to analyze the turbulence structure of fully developed open channel flows. Main emphasis is placed on the reproduction of the anisotropy of turbulence and the modeling of the effect of free surface. The pressure-strain term in the model consists of the Speziale-Sarkar-Gastki model and the Shir model for free surface effects. Through comparison on the three turbulent normal stresses and analysis of performance of the pressure-strain correlation, it is shown that the present model reasonably captures the intensified anisotropy of turbulence near free surface.

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A newly developed numerical model, based on the fully conservative flux splitting technique, by Jha et al. is further investigated. Dam-break flood waves in rectangular, trapezoidal and suddenly expanding channels are simulated to demonstrate model's ability to handle natural channel geometry. The model's response to the variations in the bed roughness and the time weighting factor is also examined.

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This paper presents the results of experimental study on walking in a stream at flood disaster evacuation. By observing the walking speed in water and people's psychology at the same time under the condition of simulated flood flow, the various condition of walking in the stream is studided. The hydraulic condition for feasible safe evacuation is obtained. The results can provide a quantitative reference for the flood disarster evacuation plan to a certain extent.

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Disaster of revetments is very complicated one which is affected by many kinds of factors. In this study, the damage of revetment is classified based on the neural network, which is one of the most effective way to perform the non-linear regression analysis. By using the neural network, the adequately high correlation between the observation and the prediction was acquired; furthermore, the dominant factors of the disaster of revetment, including some qualitative ones, are estimated

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From the investigation of various types of multiphase flows, it was concluded that the Gore-Crow criterion on modulating the turbulent intensity is valid only for shear flows. The authors propose a model to explain the Gore-Crow criterion and deduce a governing equation of the shear flow around a rotating particle.

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