Spatial surface roughness information is very important to estimate a spatial distribution of surface fluxes. In this study, by using theoretical surface-scattering models, surface roughness parameters are extracted from the backscattering coefficients observed by JERS-1 and ERS-1 and surface soil moisture volumetric content, and sensitivity analysis of backscattering coefficients and soil moisture content to the extracted surface roughness parameters are performed. In the Biwako Project area, the extracted surface roughness parameters are compared with observed ones. The extracted values and observed ones correspond well at the dry paddy fields.

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Understanding the behavior and content of soil water is important for analysis of its infiltration. Tensiometers are conventionally used to measure the suction pressure. The suction pressure is then converted into the volume of water content by using conversion equation. The problem with this method is that the water content, computed by conversion equation, is remarkably different depending on the equation used. Our research intended to give the relationship between the volume of water content and the suction pressure. Both of them were measured at the same time on real slopes by time domain reflectometry (TDR), which is capable of directly measuring the volume of water content. The volume of water content computed by TDR was compared with the water content converted from the suction pressure by the traditional method to study the accuracy and characteristics of TDR. Here, we also discuss the results of the comparison.

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Bangladesh suffered damage on accounts of the most catastrophic flood during the year of 1988, resulting in untold suffering to the people, crops were lost, lives were lost, infrastructures were damaged, and so on. The flood problem is therefore great important. The present study dealt by using MOS-1, MESSR data with other thematic maps to evaluate the affect and damage area in collaboration with land cover classification in the year of 1988, and analyse the weather condition for Dhaka and Tokyo by using ten years accession report catalogue of Landsat TM. In this paper, estimation method of flooded area on the basis of land cover classification was presented and mean value and standard deviation of clear rate for different season and probability distribution of clear rate for weather analysis was examined.

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At present we have little information about the Northern Territory Four Islands (Kunashiri, Habomai, Sikotan, and Etorofu) and also it is difficult to carry out a ground truth. In this study, the land cover classification for four islands was carried out by using multi-level slice classifier. The characteristics of the four islands' land covers were cleared by comparing each land cover classification results. Then a weather survey method by using satellite cloud coverage data of full-scene were developed. The variation cofficient of cloud coverage and the probability distribution model of clear rate, for Four Islands and eastern part of Hokkaido, were obtained.

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The May 13th tornado over northern part of Bangladesh killed about 600 people and damaged about 80 villages. Some several million dollar economic losses are counted for this nation. Besides the unavailability of modern radar information, infrared (IR) data of Geostationary Meteorological Satellite (GMS) is used in this study to observe the formation, movement, and dissipation of cloud during the touchdown of the tornado. On the basis of the meteorological identification, an attempt is made to explain the cause of the intense tornado by using GMS imageries.

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Channel changes are extremely predominant in the downstream reach of the Brahmaputra river in Bangladesh. The maximum transverse shift of the channel reaches more than 2km.
Image processing of Landsat TM data was applied to survey river channel changes. The year-to-year changes of river channels, erosion areas, deposition areas and bars were clearly visualized by the processing technique. Based on the results, the characteristics of the channel process and an influence of flood magnitudes upon them were examined.

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In this paper, flood flow characteristic of compound meandering river was investigated by using the measurement values such as hydrograph, river configuration and bed topography. The duration of a flood on a flood channel was studied, and an example scoring inner bank was found in the compound meandering flow. The river configuration represented rate of sinuosity and phase difference and the discharge represented relative depth of the channeL The velocity vector measured by aerophotograph made a correlation among the rate of sinuosity, the phase difference and the relative depth. Therefore, in this experiment, requirements of compound meandering flow and single section meandering flow were investigated.

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This study presents the observation result of vertical velocity profiles found in a small flood of the Mukawa River in Hokkaido in August 1996. The result shows that the velocity profiles in the rising stage of the flood deviate from the logarithmic law and have a steep velocity gradient; the profiles in the peak stage of the flood follow the log-law; the profiles in the falling stage again increase the velocity gradient.
The characteristic property was analyzed together with experimental unsteady flow data, by using 2-D momentum equation with the parabolic type eddy viscosity coefficient. The theoretical velocity profile derived from the equation, which has a form of Legendre differential equation, well agreed with the observation data. From the fact, it was concluded that the deviation of the velocity profile of the flood from the log-law depends on the effect of flow acceleration of the flood.

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We produced a new type rain gauge for trial, which can measure the rainfall intensity with fine time resolution by analysing the sound of rainfall emitted from a tinplate can. Digital high pass filter was designed and inserted into the data processing in order to eliminate the noise. Experimental visualization of rain drop was carried out indoors and outdoors to relate the volume of rain drop to the intensity of rain sound. The time series of rainfall intensity agreed very well with data of normal raingauge with a water collector.

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In order to estimate the sediment discharge and size distribution in moutain stream, a new method by means of collision sounds is developed.
In order to isolate the collision sound from noise, a small microphone was confined into a pipe, which was attached behind a board. When a gravel particle collides to the board, a tipical sound generates, whose amplitude is expected to distribute with some definite function for each size class.
In this paper, a new estimation method of the sediment size distribution is derived based on the factor analysis method and applied to some flume experiments.

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Various two-phase (water-air) flows occur in underground pipes like large sewer. When the pipe is filled gradually with water at flood, air may become large bubble. Then, for the purpose of researching the bubble behavior at the transition phenomenon from open channel to pipe flow, we developed the laboratory system for automatic controlled inlet discharge and image measuring water level and bubble shape and velocity. The system was constructed by motor valves, magnetic flow meters, video cameras etc. The maximum error is less than 3%. The system is useful for research of the transition phenomena.

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The purpose of this study is to investigate bed variation during a flood by a distorted model in which the horizontal scale differs from the vertical scale. Similarity laws for a distorted river model derived from dual dimensionless parameters of the bed form classification diagram for the bars and braids and the Manning-Strickler formula were used. The 9.6km reach (KP6.2-15.8) of the Chubetsu river (a tributary of the Ishikari river) was reproduced in the model. The usefulness of the similarity laws of a distorted model was ascertained, and it was found that the maximum scour depth occurs during a recession of the flood hydrograph.

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In general, river sediment is classified according to its motion into three categories which consist of washload, suspended load, and bed load. The role of each category is different in the process of topographical growth of river. For instance, a part of washload is caught by vegetation on a sand bar and makes a new flood plain. But bed load never behave as washload, but it plays only a role of the bed material. This fact shows the significance of the actual survey for the each flux of these categories.
Authors conducted sediment transportation survey on Hinuma River during the flood caused on Aug. 22nd, '96. This paper describes the outline of newly developed devices for sediment transportation survey, and some hydraulic topics recognized through the survey.

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It is important to know the exact amount of water flowing into a dam reservoir for operating a dam. Usually, this inflow is estimated from a data of the water level. Accuracy of measurement of water level necessarily reflects the accuracy of estimation of inflow into the reservoir. But, data of water level include many kind of noise, for example, seiche, wind wave, swell, and so on. In this paper, we analyzed the data of water level obtained from multiple water gauges installed in Jozankei Dam Reservoir. We found characteristic of water surface oscillation such as several kind of seiche, swell, and wavy displacement by wind. We could confirm that the wavy displace-ment of water surface caused by wind gives much error to estimate the inflow into the reservoir.

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At the design of the outlet or intake of the pumped storage power plant, it is important to consider and judge how the distribution of the flow velocity in the reservoir is. But it is very rare to observe the flow behavior in the reservoir during the operation of the pumped storage power plant. We observed the flow velocity, the water temperature and water turbidity in the reservoirs of the pumped storage power plant, to clarify the behavior of the water flow by the running of the power plant. The results of the observation show that the outlet flows is not widening very much and the decrease of its velocity is small, and the horizontal velocity is more enormous than the vertical velocity.

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The velocities of two-layer flow system at the river mouth of the Ishikari River were measured by ADCP, which enable to estimate the river discharges. The present measurements show that the density interface can be discriminated from the profiles of echo intensity, hence the mean velocities and the resulting flow rates of upper and lower layer can be estimated correctly. The gradient Richardson number calculated from vertical profiles of velocities and densities changes every moment and the tendency is found to be different from that of the overall Richardson number. The measurements provide important results in analyzing stability and mixing at the density interface.

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The Lake Abashiri, located in the northeast of Hokkaido, has stratified layers of fresh and salt water. The biochemical pollution caused by inflowing load from the catchment area, and no oxygen state of the lower salt layer is becoming a serious problem. One of the important phenomena on this problem is the alternate directed density current of the Abasiri River, which goes into the Lake Abashiri. A 180 degree bend is existing in the Abashiri River at one km downstream of the lake, and this makes the hydraulics of the system more complicated. In this study, a series of field measurements on three dimensional flow field and density of river water were conducted in this bend in 1986. Two set of measurements in melting snow season and low flow season when the unidirected flow from the lake and the alternate directed stratified flow becomes dominant, respectively. ADCP (Acoustic Doppler Current Profilers) and STD (Salt Temparature and Depth) were used to collect the data continuously in a wide area within a short time. Collected data are compared with existing theory and the characteristics of the stratified density flow are discussed.

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Acoustic Doppler Current Profiler (ADCP) was used for the observation of flood flow intruding into a reservoir. The data had a lot of error which was generated by rolling and pitching of a carrying boat. We investigated the characteristics of the error in order to develop. a data correction method. In this paper, a least square method with non-linear weight function is shown to be useful for the determination of a series of trial functions which interpolate the very fluctuating original data properly. The corrected velocity field is consistent with the profile of the turbidity layer which was measured with a sonar and a turbidity meter.

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The flows in two types of open channel trench are experimentally examined by using PIV method and are numerically analyzed by k-ε turbulence model; Considered here are the flow in the full width trench and that in the half width trench. The spatial distribution of instantaneous velocity vectors and turbulent flow behavior are clarified in the trench section using PIV. Mean flow velocity and Reynolds stress measured by PIV are compared with those simulated by k-ε turbulence model. The flow characteristics obtained by the two methods agree with each other fairly well.

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In an open-channel flow, a turbulent structure is affected by the presence of a free surface, and therefore, its characteristics are quite different from those of duct flow near the free surface. Many researchers have suggested that the turbulence redistribution changes complicately near the free surface. In this study, turbulence measurements were three-dimensionally conducted in open-channel flows by using two sets of twocomponent fiber-optic LDA. Some comparisons of the experimental LDA data with a direct numerical simulation (DNS) were conducted. Then, the peculiar characteristics in open-channel flows were clarified in detail

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Vegetation in rivers decreases the flow capacity and therefore has been removed from river basin. However, the importance of vegetated zone in rivers has recently been recognized not only for river management but also for water flow environment. Turbulent structures of vegetated open-channel flows and the associated sediment transport are investigated by some researchers.
In this study, turbulent measurements in partly vegetated open-channel flows were accurately conducted by using a fiber-optic laser Doppler anemometer (FLDA). Basic turbulent structures such as mean velocity and turbulence were experimentally obtained and discussed as comparing compound open-channel flows.

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The Acoustic Doppler Velocimeter (ADV) is used to determine 3-D flow characteristics of small scale river Maeda.Even if the flow of the river has very complex 3-D characteristics owing to sand waves of the bed, vegetation zone of the side walls and trapezoidal shape of the channel, it is recognized that the turbulent characteristics of the river has highly similarity to the flow in the model channel examination. The frequency response of the ADV to the velocity fluctuation has good agreement in the range from region of the energy containing eddies to the inertial subrange in universal equilibrium region of power spectrum.

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Measurements with X-type Hot-film anemometers inherently involve errors caused by an overheat-ratio, Reynolds number and the length-to-diameter ratio. In this study, the influence of the overheatratio and the Reynolds number on a cooling factor k was investigated experimentally. It was found that the cooling factor k is not affected by the overheat-ratio in a range of 1.03 to 1.05, and the Reynolds number in a range higher than 15.2. The cooling factor k is affected only by the length-to-diameter ratio. The cooling factor k decreases with increasing the length-to-diameter ratio.

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Color pictures from a high-speed color video system was used in measurement of the internal velocity fields by the correlation method. Color pictures provide three-times more information than monochromatic pictures, allowing more detailed analysis of fluid motion under breaking waves. By taking this advantage, the comparative investigation was made on the internal velocity fields of solitary wave on a fixed bed and on a movable bed.

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Laser-beams or -sheets is applied as detection sources of a flow with solute or particle suspension. The concentration field is estimated inversely from the integrated information of the light intensity attenuation by means of CT-scan technology. The instrument can measure quasi-instantaneouly and quasi-continuously a 2D concentration distribution of sediment.
The principle of the inverse estimation of concentration, the design of the instrument and a preliminary test result are described.
This research aims at (1) the practicability to handle in laboratories and fields, (2) a lower price at which common users can purchase easily, and (3) compactness without disturbing the flow field.

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A prototype of measuring instrument using a laser CT scanning method, was developed for nearly instantaneous spatial concentration distributions of turbid liquids, such as sediment, in a cross-sectional plane field, which may be one of the very important factors to solve problems in hydraulics, rivers, coastal engineering, etc. The instrument was constituted of a scanning multipoint laser light transmitting unit, a photo detection array unit, a control unit, and a personal computer with signal and data processing software based on the principle of the inverse estimation. Some laboratory test for a real concentration field proved the usefulness of the instrument.

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The object of this study is to develop a method for estimating both the ground thermometric parameter (ρ c λ) and ground conductive heat flux (G) simultaneously by using the ground surface temperature (Ts). This method is based on the Fourier series expressions of the result of heat transfer equation. The method is tested by a field-measurement. The following results are obtained: 1) The estimated ρ c λ have a reasonable value. 2) Estimated diurnal variations of G agree very well with that observed. 3) The spatial distribution of ρ c λ is also estimated from the surface temperature distribution obtained by the thermo-graphy.

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The aim of this study is to show the methods to measure and estimate a local atmospheric CO₂variations. At first, we use an apparatus which is over 10 times cheeper than other apparatuses used in other reports, and show that the daily variations of CO₂are affected by vegitation. Secondly, the relationship between a satellite-derived vegitation index and the seasonal CO₂variations is investigated.

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Prediction of long-term changes in temperature is of vital importance for estimation of future available water resources. An observed 238-year monthly temperature time series is investigated by chaos theory and use results from the analysis to make short-term predictions in real-time. We use the Lorenz equation as a reference system of equations and the extended Kalman filter to identify the structure of the governing system and make updated predictions. The results indicate that predictions can be made for filtered monthly temperature time series if the prediction lead time is short. Parts of monthly temperature variation at a point may follow a chaotic time trajectory as influenced by large-scale atmospheric flow.

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To successfully model global energy and water cycles, the linkage of the hydrologic model and atmospheric model is required. We present a strategy to build a macro hydrological model to be combined to an atmospheric model.
First we present a way to combine the field models of the atmospheric and hydrologic systems, in which the natural catchment shapes can be used as macro hydrological grids. This makes us to utilize the experience in hydrological modeling of watersheds.
Second we present a strategy to build simplifieddistributed hydrological models of the processes within each macro hydrological grid. We take into account topography and stream network structure to derive simplified models, using the cluster analysis and stream order analysis. This type of simplification will be useful when considering the heterogeneity of hydrological state variables within a grid.

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Forest canopy can divide raindrops to minute water droplets by collisions with branches and leaves. This may promote evaporation and suspension of water and influence the water budget in forest area. Therefore, we investigated the size distribution of minute water droplets caused by the collisions. Experimental results showed that the size distribution of droplets could be represented by N=N₀exp (-ar³-br²), where N, r: number and radius of droplet, and N_o, a, b: constants, better than by exponential equation especially in both ends of distribution curve. Estimated evaporation during 20m fall of minute droplets was about 1-3%.

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This paper describes the cruising speed of fresh water fishes. Most of the previous studies about measurement the cruising speed have not consider spatial and temporal distributions of velocity of water flow. We made experiments on cruising speed in open channel which has gravel water bed.
The experiment result indicated that the cruising speed was a few times as fast as the cruising speed measured in the past. This difference is though to be due to non-uniform distribution of flow velocity. This result indicates that small spaces with low velocity area are important for aquatic organism. This study shows that the spatial distribution of flow velocity is more important than the mean velocity to understand behavior of aquatic life.

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At present, lacking hydraulics study, the design of texture of falling water depends on the experience of each designer or a test study for each case. For the first step to construct a systematized engineering design method, a full scale experiment was carried out and the texture of falling water was classified into three categories for both free falling and slope falling water. According to the limit of the law of similitude, computer graphics (CG) were introduced for the design method instead of a reduced scale model. Further study of hydraulic mechanisms and of design methodology are proposed for the next step in the design of texture of falling water.

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A field observation was made to investigate turbulent characteristics in the lower region of an atmospheric boundary layer in day and in night. Horizontal and vertical wind speeds, and wind direction were measured by using a doppler sodar at 13 points in the range of 55m to 425m above the ground. Vertical profiles of the mean wind speeds, the Reynolds stress and the turbulent intensities were obtained from the measured data. The diurnal profiles were compared with the nocturnal ones. Their profiles show that the diurnal boundary layer had a strong convection caused by the solar-heating and the nocturnal layer was relatively stable. The Reynolds stress decreased linearly with height both in day and in night.

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There are much vegetation in a river bank Vegetation has a role of protecting banks as good. On the other hand, it has a bad role of being rose the water level.So, we should make a river course planning which is desirable for both of the river environment and flood control by using vegetation.
In this paper, vegetation is attempted to use as a groin. It is experimented by a curved channel withmovable bed and investigated the flow and bed topography around the vegetation groin, and considered about the possibility of vegetation use as a groin.

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The accuracy of GAL model, recently developed by the authors for a new formulation of dispersed-phase motion in a multiphase turbulent flow, is examined for convective numerical simulation. To reduce numerical diffusion inherent in the previous scheme of reallocation procedure of the GAL model, a new reallocation scheme is presented. The computational results for idealized convective transport show that the improved GAL model has high accuracy, being comparable to 6-point scheme, and high numerical stability even for the flow condition of Courant number greater than one.

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The flow structure of meandering compound channel between straight levees with fixed flat bed have studied recently and at present knowledge about that field is improving. To investigate the effect of levee alignment on the flow, we experimented two cases of flow which had different phase of meandering between levees and main-channel. In the first case, where the meandering of levee goes ahead of that of main-channel, dead water area appeared and the flow became narrow. In the second case, where the meandering of levee goes behind, flow occurred all over the channel.

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The purpose of this study is to develop the analysis method for debris flow with soft computing. The soft computing methods which embrace neural networks and/or genetic algorithms (GA) are expected to solve problems which are defined imprecisely from a complex phenomena.
The neural network combined with the GA was introduced into the analysis for the occurrence condition of debris flow. Training data sets to the LVQ network are optimized by the GA. Theprocedure was used to examine a characteristic change in occurrence condition of debris flow. Runoff analysis of debris flow by the use of GMDH was proposed. These methods were applied to the data for the Mizunashi River in the Unzen Volcano. The results led that the soft computing methods are useful for data analysis of the debris flow.

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The effect of wind on an open-channel flow is investigated by changing the flow direction in the channel. It is found that the efficiency of momentum transfer from the wind to the primary flow in the channel depends strongly on whether the channel flow is favorable to or against the wind direction. This is because the wind-driven secondary flow that consists of a pair of Langmuir-like circulations not only controls the redistribution of horizontal momentum in the channel, but also markedly affects turbulent diffusion from the nearsurface toward the channel core.

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