The probable maximum precipitation (PMP) is very important in river planning. The traditional approach to PMP determination is mainly based on the moisture maximization of observed extreme precipitation amounts and its regional distribution is obtained by smoothing the point data of PMP. But in geographically complex areas like most of Japan, it is difficult to smooth the data of PMP. This is because the wind field is affected by geographical features, so the atmospheric condition and precipitation process can make a large difference in relatively short distances.
Therefore in this paper, using a 3-D wind field simulation model, three parameters indicating atmospheric condition like CAPE (convective available potential energy) that could be related to the heavy rainfall are evaluated. Then the regional distribution of PMP is estimated using these parameters.

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To improve the accuracy of the radar-estimated rainfall, we observe and analyze the vertical profile of the rain drop size distribution (DSD), then create a new formulation of vertical profile of DSD related to rainfall type and build up an algorithm for estimating ground rainfall using radar. Observation of the vertical profile of DSD is carried out by a vertical pointing VHF Doppler radar named the MU (Middle and Upper) Radar, which can detect vertical profiles of Doppler spectrum that composed of bothrain drop itself and air movements.

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A method for observing the cumulus scale disturbance of water vapor by using GPS is proposed. This method has a characteristics that the disturbance of water vapor at high elevation is divided from it at low elevation. The following things are detected by investigation of the method using model atmosphere which was calculated numerically by using two dimensional cloud microphysics model.
·The position of disturbance of water vapor at high elevation is estimated reasonably by using a couple of satellite radio.
·The origin of the disturbance of water vapor at high elevation is estimated using high density GPS observation network.

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Sensible heat flux of urban canopy layer were estimated by a numerical model which was developed by adding the effect of urban building canopies to a meso-scale turbulent closure model. The model was tested with different kinds of canopy density. The Results of computations indicated that the sensible heat flux at road surface and roof suiface depend much on the building density and wind field within the canopy layer.
The results also indicates that the numerical model is needed for understanding the real heat balances, and wind and temperature filed.

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In small urban rivers, floods occur almost every year not only because of typhoons but also concentrated heavy rain such as thunderstorms. To implement the flood control plan adequately and flood prevention activity quickly, it is necessary to understand characteristics of the concentrated heavy rain. In order to forecast the occurrence and movement of thunderstorms and deal with them, it is important to make clear the relationship between thunderstorms and their meteorological factors.
In this study, the relationship between thunderstorm occurrence and wind convergence is studied for the Kanto plain, which is the largest plain in Japan where the geometrical effect may mot be included.

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In winter seasons Snow clouds occur in front of a cold air flow which extends from the land to Ishikari Bay. Purposes of this study is to obtain the mechanism of the relation between snow clouds and a cold air flow. In order to know the effect of the cold air flow, Sturation Equivalent Potential Temperature (S. E. P. T), E. P. T and P. T. were obtained by using radiosonde data before and after snow clouds occured and we used ARPS (Advanced Regional Prediction System) which was developed in the University of Oklahoma. As a result, the radar intensity data and the calculation results agreed greatly.

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The urban climate characterized by heat island and the cooling effects of green district was investigated through field observation in Kanto area. Especially considering influence of river environment and sea breeze in boundary layer, meteorological quantities (wind profile, specific humidity, temprature) was measured with doppler sodar and three tethered balloons. The temperature inside surface layer (altitude 10m-50m) was found to be different in the maximum 5°C between flood plain and urban area. Two types of discontinuous lines formed between sea breeze and mountain wind from the mountainous area were found. Along these lines, frontal thunderstorm were induced.

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Numerical simulation of Kanpachi cloud, i. e. generated just over the Kanpachi Street under calm and clear atmospheric conditions, has been performed by RAMS (Regional Atmospheric Modeling System). The method of Four-Dimensional Data Assimilation (4DDA) and Nest Grid System, the most advanced meteorological prediction techniques, are used in this simulation.
Simulated wind field and cloud in the morning predicted by the model agree very well with those of the observation by Kai et al.(1995). Additionally, the cloud line that was observed in the afternoon and a local convergent flow due to two sea breezes (one from Sagami Bay and another from Tokyo Bay) could also be simulated although the simulated cloud is rather underestimated. These numerical results suggest that Kanpachi cloud in the afternoon has some different mechanism from that in the morning such as aerosol effect of urban pollution to cloud formation.

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A river has the effect of climate alleviation not only as a cool spot but also as a so called wind channel. Statistical analysis shows the penetration of sea breeze front over Kanto plane classified into two cases, East or South-wind, influenced of synoptic scale. In these two cases the characteristics of penetration of sea breeze front were investigate on three scales (1) wide area (Kanto plane), (2) urban (Tokyo), (3) river (Ara river). Especially, as a result of meteorological field observation conducted along Ara river in detail in this summer, a typical urban river lead the sea breeze front to inland as a wind channel when South-wind matched with river flow. Around secondary scale, Tokyo, the penetration of sea breeze front are blocked over urban area because of heat island, then the front may be surrounding there.

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LES simulation method has been developed for atmospheric flows over three-dimensional complex topography with and without temperature stratification. Rather than using the conventional equations of motion, it uses a spatially filtered form of equations for flow in porous medium, which allow a convenient way of representing complex boundaries using rectangular or other non-boundary conforming grids but simpler to write a computor code. After some validation runs are made for flat terrain for which published simulation results are available, computations are performed for an isolated idealized three dimensional mountain on a flat plane and the results are compared with experimentals and calculation results by other workers. The present computation agrees with experiments qualitatively, with some differences attributable to anavoidable differences in the computational conditions.

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A new type of water-retentive ceramic tile using industrial wastes as raw material has been developed. The tile has pores with an average size of about 10 micrometers, and, in a saturated condition, has a volumetric water content of more than 40%. Its moisture retention curve is quite unique, different from any kind of traditional types of tile. The performance of the tile was tested by exposing water-saturated tile to the sun in summer. In the test, the surface of the tile was more than 10°C cooler than the concrete roof. In another test, a tile pavement at a housing complex was sprinkled with water and the surface temperature of the pavement was measured.The test showed that the surface temperature of the pavement were also low and the temperatures of air directly above the pavement were lower than the ambient temperature by 1 to 2°C. The reason for these phenomena was found out to be that heat was consumed as evaporative cooling latent heat so that the surface was cooled.

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A numerical model has been developed for the simulation of heating and evapo-transpiration processes in the plant canopy. Heat and moisture fluxes at the soil surface are evaluated by solutions of equations coupling subsurface heat and moisture transfer, and the evaporation at the ground surface. The heating and transpiration processes in the plant canopy are computed using a model coupling the foliage heating and water transport in the soil-plant system. The plant canopy is divided into layers with LAI in each layer equal or less than 0.1; and stomatal conductance and photosynthesis of leaves in each layer were simulated. The model for transpiration in the plant canopy includes a submodel for the absorption of water in the soil by root, a submodel for the transport of water in the stem, and a submodel for the transpiration at the leaves. Details of the air temperature, specific humidity and wind velocity inside the plant canopy are also investigated.
A verification of the model using a field observational data at Tsukuba, Japan reveals that the model can simulate satisfactorily the mass and heat transfer processes in the plant canopy. Due to its general type, the model can be used to predict the heating.

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Soil wetness distribution on the land surface is important to the climate of the Earth. For example, the Asian summer monsoon has been suggested to be drived by air heating on Tibetan Plateau. Recently, a continental scale data set of soil wetness has been generated from the satellite-based microwave radiometer. This data is available except for the areas covering with plants or snow. To get the spatial distribution has a merit to use with a global circulation model. In this study, we compared between the soil wetness index derived from remote sensing and the soil wetness derived from running a column-type land surface scheme used in the general circulation model. It was found that 1) setting of a soil thickness, 2) considering run-off and storage processes of the land surface scheme and 3) a horizontal distribution of a precipitation are important to incorporate soil wetness derived from remote sensing into GCMs.

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In this paper, we discuss the LSP (Land-Surface Parameterization) that should be used to achieve the objective of the Lake Biwa project from modelling part. One of the suitable models is SiBUC which have been developed by authors, since it can describe the heat budget characteristics of each landuse-vegetation area, urban area, and water body.
This model's output can be fitted to the observation data by adjusting some parameters in the model. By adjusting four optical parameters and two physiological parameters, heat budget characteristics of paddy field is well simulated. Some optical parameters and heat properties for urban area are also adjusted.

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In a regional climate model, it is difficult to determine the initial field of soil moisture. In this paper, we use a version of CSU-RAMS (Regional Atmospheric Modeling System) that has been modified at NIES (National Institute for Environmental Studies) as a regional climate model for Eastern Asia. A simple bucket model is implemented as a land surface hydrological scheme. Numerical simulations are carried out for the first two weeks in August 1994. The importance of soil moisture to near-surface atmospheric parameters (temperature and relative humidity) is examined, and local soil moisture adjustment for the near-surface atmospheric parameters using the method of ‘soil moisture estimation’ is tested. The ‘soil moisture estimation’ significantly improves the biases of the near-surface atmospheric parameters. As a consequence, the possibility of adequate determination of the initial soil moisture is suggested. In addition, it is found that the adequate precipiation rate may, in some cases, improve the soil moisture field without the ‘soil moisture estimation’. These results should be validated against the water balance consideration in the future study.

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Field experiments have been carried out in the United Arab Emirates since 1996 to explore post-irrigation drying processes in sandy loam using in-situ thermo-hygrometers.
In our “soil thermo-hygrometer” method, time variation of relative humidity in the soil pores at different depths is used to detect the position of the downward propagating drying front associated with the uppermost dry layer. After irrigation, the drying front reaches at depths of 0.05m and 0.1m after 4 days and 9 days, respectively. Moreover, the transport of sensible heat between atmosphere and ground surface is obtained from the heat energy budget of the ground surface layer, whose thickness is taken into account.
The field experiments demonstrate that the “soil thermo-hygrometer” method is valid for monitoring the development of the uppermost dry layer due to the evaporation from the soil.

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The backscattering coefficients observed by synthetic aperture radar (SAR) are influenced by surface geometric roughness obstacles. Using this attributes, spatial distributions of aerodynamic roughness parameter are estimated from the SAR images obtained by the Japanese Earth Resources Satellite (JERS-1). By the method, it is possible to make roughness maps which are very similar to roughness maps derived by the method proposed by Kondo & Yamazawa (1986) which uses the National Land Numerical Information.

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The objective of this study is to develop an algorithm for mapping soil moisture by using the spatial and temporal distributions of the microwave backscattering coefficients of the ground surface. The scattering model that includes Integral Equation Method (IEM) are applied to the two images of L-band Synthetic Aperture Radar (SAR) mounted on JERS-1 taken over the Tibetan Plateau in January and August, 1993. The backscattering coefficient of the ground surface is affected not only by soil moisture but also by the other factors such as surface roughness, vegetation and soil composition. To obtain the values related to roughness, the ground-based measurements are carried out “GAMETibet POP” in summer, 1997. Two experimental areas with different surface characteristics were selected. The soil moisture map in August was derived from the scattering model with the relationship between two surface roughness parameters inputted. The distribution of the calculated soil moisture on the Tibetan Plateau corresponds to the result of the field inspection.

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The tank model is a flexible runoff model which has been utilized for the analysis of long term or short term runoff. However it has difficulties to decide the suitable coefficients in the model.
The relationship between those coefficients of the tank model and the basin condition was investigated for a construction of the model. The coefficients could be evaluated from some information in the basin. These information can be obtained using GIS data made by the Geographical Survey Institute. The investigation was made at four watersheds in upper region of the Tone river. Firstly, the coefficients of the tank model were decided by Standardized Powell Method and runoff data were represented by the estimated coefficients. Secondly, every coefficient was compared with the basin condition by GIS data.
As a result, the relations between some coefficients of the tank model and representative topography conditions, basin area, soil and geology conditions, land utilization of the basin, and so on, are confirmed.

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The tank model is useful for runoff analysis since it can represent non-linear stream flow behavior. It is difficult to properly identify a lot of parameters of the model from observed data. The genetic algorithm (GA) is a search procedure based on the mechanism of natural genetics and is efficient for the global optimization. On the other hand, the uncertainty of the identified parameters, which may significantly affect the prediction of the stream flow, should be taken into account.
This paper describes the statistics of the identified parameters using the GA. The statistics is evaluated by the bootstrap method to simulate the data fluctuation. Furthermore, the information criterion EIC which is derived from the bootstrap method is introduced and applied to select the best tank model.

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The objective of this study is to develop an distributed snowmelt analysis system using conventional hydrometeorological data. This system consists of two subsystem: one for runoff generation and the other for channel routing. In this system, watershed is devided into grid blocks connected by a channel network which is derived from altitude data at central points of grid blocks. In runoff generation subsystem, the runoff from each grid block is calculated by using a snowmelt model based on radiation budget, and the XinAnJiang rainfall runoff model. The runoff is then routed to the study points using the kinematic wave model in routing subsystem. Sample calculations with respect to the Uono River basin resulted in a good correspondence between predicted and observed hydrographs due to snowmelt.

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This paper describes observations of snowmelt runoff with frozen soil in the Tomisato dam experimental basin. Observed results are indicated as follows: 1) the ground surface soil at the hillslopes was always freezing, 2) there was rarely frozen soil near the stream channel because snowpack serves as a good thermal insulator, 3) the diurnal change of snowmelt runoff was rarely recognized except in the maximum snowmelt season and 4) the swell of long wavelength of hydrograph occurred in the early snowmelt season.
To make clear the cause of above runoff characteristics, this study focuses on the overland flow over the hillslope surface and subsurface flow infiltrated in soil layers. By applying a 4 × 3 zoned tank model, it shows that the effects of frozen soil on the snowmelt runoff are estimated by the value of model parameters.

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The purpose of this study is to develop a 2-D soil model for heat and water transfer in permafrost regions.It was suggested by the field observation on the Tibetan Plateau that the local topography affects considerably the distribution of soil moisture and temperature and the active layer depth, that is, the lower soil temperature, the higher soil moisture and the more shallow active layer at the bottom of the slope. To incorporate the effect of horizontal soil water movement on vertical heat and water transfer in permafrost regions, a 2-D permafrost model is developed in this study. The numerical simulation by using the proposed 2-D model shows that the model can express the adequate distributions of soil moisture and active layer depth which correspond to the observed ones qualitatively.

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The methodology has been proposed in which (1) a river basin is divided into a number of grid boxes;(2) runoff processes in each grid box are modeled;(3) these grid box models are connected in order to build the total runoff system model of the river basin. This paper reports the grid-based dynamic wave model and its application. If the dynamic wave model is used to calculate a large scale river network flow, it costs too much calculation time and computer memory. To save them, the technique is proposed by which the simultaneous equations with unknowns of whole sections are transformed into ones with unknowns of only boundary sections. Finally the model is applied to simulations of river network flow.

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A physically based distributed mathematical hydrological model has been developed and applied into two moderate size catchments, Ping river basin in Thailand 1) and Agno river basin in the Philippines 2) of catchment areas 3300 km² and 1600 km² respectively. The model performed well in simulating the behavior of different hydrologic components in these two river basins. In this research, the model has been applied in the Chao Phraya river basin upto Nakhon Sawan, comparatively large river basin with 62, 716 km² of catchment area. The simulation of hydrographs are better in the mountainous side of the catchment than the relatively flat side of the catchment. This is because the DEM in the mountainous side is better and generated rivers match the actual rivers. On the other hand, DEM of flat area is not good and generated rivers are not matching with actual rivers.

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A distributed model of water and heat transfers is described at first. The subgrid heterogeneity of land use is considered by using a nesting method. Evapotranspiration and latent heat flux are computed by the Penman-Monteith equation, infiltration excess during heavy rains is simulated by a generalized Green-Ampt model whereas saturation excess during the remaining periods is obtained by balance analysis in unsaturated soil layers. Surface temperatures are solved by the Force-Restore method. Two dimensional groundwater flow is simulated to consider the interactions between grid cells. The river flowrouting is conducted by using the kinematic wave method. The model is applied to the middle-reach catchment of Tama river and it is verified by the observed discharges at the catchment outlet in the threeyears from 1992 to 1994. Finally, sensitivity analysis shows the effects of input data and model parameters on annual water and heat balances.

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In this paper, the authors propose a cell-based distributed runoff model using raster spatial data such as digital elevation models (DEM) and remote sensing images. This paper also describes how the hydrograph simulated by the runoff model changes as the spatial resolution of the raster data becomes coarser. The study area is the Yada River basin (110km²) in the Shonai River drainage system. The runoff model is evaluated using raster data with 50-m resolution and 250-m resolution. Consequently, the hydrographs simulated by the runoff model with 50-m resolution are not sensitive to the model parameters values than those with 250-m resolution.

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A physically based distributed model, consisted of grid cell-sub-model of SVAT type and river routing sub-model of linear reservoir type, is proposed. Grid cell-specific meteorological variables are produced by a special regression method and applied to the Fuji River basin divided into 3, 376 grid cells. On the other hand, the basin is regarded as one grid and a lumped model is considered, with its input being the averages of distributed data. Then these two models are compared as for differing situations. They give similarly good runoff process when rainfall on basin is large and relatively uniform. However they behave differently when rainfall is not large and very non-uniform in spatial distribution. The lumped model underestimates flood peak flows. And the distributed model is applied to analysis of hydrological response to possible landuse change, while it is difficult to do so with the lumped model. Conclusively distributed model could be more appropriate than lumped model for a large basin.

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The grid-based distributed hydrological models are powerful tools for hydrological modeling due to the representation of the spatial varibility and the physically-based process descriptions. However, because of the large computational demands this kind of models are not suitable for long term simulations in large catchments. Here, an alternative distributed hydrological model is proposed, which is based on the catchment geomorphology area function and width function. In this model, the catchment is discretized into a number of flow intervals along the flow direction. Each flow interval is represented as a series of hillslope elements. A hillslope response model and the kinematic wave model are used to simulate the runoff generation and river routing. The applicability of the model for the simulation of multiple catchments is discussed in the paper.

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An effect of the stochastic nature of soil properties related to the water movement on the infiltration was examined and evaluated by using Philip's equations. The aggregation criteria are derived from them for four parameters, hydraulic conductivity, bubbling pressure, saturated water content, and a parameter for soil water retention curve and are expressed with the tolerance error and their moments. The criteria for the cumulative infiltration are more strict than for the infiltration rate if both tolerance errors are the same, and it is enough to check the former only. Comparing the criteria with measured variations of soil parameters, the authros have found that the parameter averaging method is good for bubbling pressure and saturated water content, the second order moment method good for the retention parameter, and the infinite order moment method good hydraulic conductivity.

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Generally, the calculated discharge is an output that passes through two low pass filters, a discrete system and a runoff system. A discrete system accumulates the real rainfall which is continuous over a period of time, Δt. The output from the discrete system is an input to runoff system described by runoff models. The optimal time interval, Δt, depends on a runoff system or mainly basin scale. In this paper, we adopt Kinematic Wave equation and two kinds of storage function runoff models derived from Kinematic Wave equation as runoff models and introduce an extended frequency response method to evaluate the optimum time interval, Δt.

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The concept of the diffusive tank model is that, as the water level of drainage channels changes very slowly due to a backwater effbct inalowing-lying drainage basin, the unsteady flow in the channel can be simplified to a nonunifbrm flow.
This paper applies the diffusive tank model to runoff analysis in a low-lying drainage basin which is about 1.7km², and to investigate the hydrological characteristics of low-lying basin by runoff prediction after the paddy field consolidation. The results are summarized as fbllows;
(1) The results of flood routing analysis by the diffusive tank model show a good coincidence with observed hydrographs.
(2) After the paddy field consolidation of low-lying areas, herunoff prediction in future is performed.

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Consciousness of the environment has raised in recent years. Many municipality corporations began conserving and reviving the ecological river front in urban areas which was deteriorated by urbanization. The first procedure for the river front conservation is to increase the ordinary water discharge of urban minor rivers, and the basic study for that is to clarify the hydrological cycle of such river basins.
The present paper analyses the hydrological cycle in terms of groundwater runoff, direct runoff and groundwater storage in the Azuma upriver basin during 76 days in 1996, using the daily hydrological model for an urban basin which was presented by Ando et. al.(1982). The simulation resulted in approximation to the observed runoff hydrograph and the groundwater storage which was derived from the measured groundwater level. This paper also predicts the runoff hydrograph in the same period using the same model on the supposition that houses infiltration facilities are set in this basin. This simulation demonstrated that the groundwater runoff was increased and the direct runoff was reduced, that effect on restoring the ordinary water discharge.

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Combined sewer overflows (CSOs) have made water quality of receiving water bodies, including rivers and lakes, worse year by year. A new distributed runoff simulation model of storm water and pollutants in urban sewer pipe systems, which can be used to investigate appropriate counter measures for the CSOs and evaluate the effects of the measures, is proposed.
In this model, PWRI Model, which is a lumped model and was proposed by the Public Works Research Institute, Ministry of Construction, Japan, is improved to a distributed model that can treat a back water effect.
Simulated pollutographs by the proposed model are compared with simulated ones by PWRI Model as well as observed ones at a pumping station, and the adaptability of the model is investigated.

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In order to get an appropriate method for reproducing stream channel calculated from the digital map with 250m lattice size, various definition of stream source and connection are examined at first. The major indices of topographic feature on the stream order defined by Strahler, bifurcation ratio, length ratio, area ratio and slope ratio are measured at four stages of lattice sizes in the next. And, changes of the indices due to aggregation of channel network obtained from the four lattice sizes are discussed. At last, in order to get surface runoff response characteristics of distribution of the concentration time calculated from those lattice sizes are discussed.

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The global warming phenomenon has become of major interest in recent years. The objective of this study is to evaluate the effects of the global warming on precipitation, evapotranspiration, and runoff discharge in two different regions with and without much snow and snowmelt in winter and spring. Two types of future temperature scenarios: Time series scenario and 1°C increase scenario, are employed for predicting the future changes of monthly mean temperature. The occurrance number, duration, and daily rainfall amount of one storm cluster in each month for two warming scenarios are evaluated by the nonstaionary time-series model of rainfall characteristics (Nagura and Hashino, 1996). Future monthly evapotranspiration is estimated as the sum of transpitration and rainfall interception loss. Monthly mean runoff discharge is estimated by the stochastic response model of daily runoff (Yue and Hashino, 1996)

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The role of vegetation on water balance in mountainous region has been discussed for long time, however, the quantitative evaluation of the role has not been clearly. Meantime, erosion control works have been extensively carried out since the end of the War, for recovery of ruined country. Now, it becomes necessary to evaluate the effects of erosion control works quantitatively. We have started observations of rainfall, discharge and sediment runoff at 5 experimental basins located in upper Watarase River, in order to evaluate the effects of erosion control works carried out in the basins. This paper is a result of preliminary study concerned to change of runoff characteristics of Watarase River at Kusaki Dam site, which includes 5 experimental basins and is 254km² in area.
The results obtained are as follows: The long term runoff characteristics has been changing inthe direction of becoming lower runoff ratio. Intensities of flood peak are becoming mild. These results are obtained using the data during 1977 to 1995, so, it seems too short to judge correctly. We must confirm these results using the data of experimental basins in future.

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Headwater basins may have alleviation functions of flood and drought. It is indispensable for designing the policies of flood control to evaluate the flood alleviation function explicitly in headwater basins. This paper focuses on the influence of canopy density on the flood alleviation functions of forests. The change of the spatially averaged canopy density due to the annual forest thinning for 6 years is evaluated in a forested mountain basin. The relationship between the spatially averaged canopy density and the rate of peak flow is investigated on 41 flood events for 6 years. It is clearly shown that the reduction of canopy density due to the forest thinning causes the increase of flood peak flow. It is suggested that rainfall interception due to forest trees affects the change of peak flow based on the results of short-term runoff analyses in the basin.

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A mathematical model of NO_3^--N runoff process from a forested mountain basin is developed, based on a tank model comprising a surface tank with soilwater storage systems, and a groundwater tank. The model takes account of three elementary processes of NO_3^--N in the forested mountain soil, (a) advection owing to the rainwater movement, (b) solute exchange between mobile and immobile regions, and (c) nitrification by microorganisms in the soil. The nitrification process is modeled using an exponential function of air temperature.
The proposed model is applied to annual observations in 1992 obtained in Shirakawa-tani forested mountain basin (main species Japanese cedar) located on Shikoku island in Japan. The model describes the seasonal change of NO_3^--N streamwater concentration through a year. But, it is found that the model has underestimates objects at the beginning of summer. The deviation may be caused by not using soil temperature, but using air temperature data.

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The objectives of this study are to simulate pollutant runoff from a small river basin in an urban area, and to estimate the effect of the 1994 drought on pollutant runoff The simulations using the series of precipitation data of 1994 as a drought year and 1986 as a normal year were done by the Water Quality Tank-Model. As a result of the simulations, findings were:(1) The amount of annual runoff pollutant load in 1994 was almost same as the amount in 1986.(2) It was proved that the pollutants which had accumulated during a drought period of 1994 summer, ran off at a stretch by a large storm in the middle of September. And (3) it had a great influence upon water quality in receiving water.
In the result, some available information for the environmental management of water in urban areas during a drought period have been obtained.

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Acid rain is caused by raindrops that catch nitrogenous compound of suspension etc in the atmosphere.
In this study, firstly, acidity of rainwater samples which are collected in Tochigi region is investigated. Next, the changes of some ion concentrations in the soil are investigated in thunderstorms.
As a result, although distributions of acidity are influenced by many factors such as atmosphere, topography, climate and so on, it is clear that distribution of pH units is different by the change of climate patterns in this area. And it is shown that pH units at every rainfall roughly classified in to a front type, typhoon type and thunderstorm type. From inspection of ion concentration distributions in the direction of depth, it is shown that pH unites range from 4.6 to 5.4 and it is thought that there is large influence on the plant within a depth of 30 cm from the ground surface.

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This study investigates the secular change of monthly, seasonal and annual precipitation, and the change of the monthly precipitation by each weather factor in Nagano prefecture. The weather factors are cyclone, trough, front, typhoon, winter monsoon type pressure pattern, the instability of atmosphere, the other factor and the precipitation of total factors. The secular change of precipitation, which reaches a synthesis time series, increases or decreases repeating periodic variation regularly or irregularly. The monthly change of precipitation expresses well the characteristic of precipitation by each weather factor. Besides it is known that the cyclone, the front and the typhoon have a lot of precipitation from the monthly change. The result obtained is very important for a future water resources project in Nagano prefecture.

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An optimization model of a user interface for flood control supporting is developed to analyze the human evaluation mechanism. In the design model proposed here, the evaluation function of the user interface is its users. The optimum combination of various types of display elements are automatically searched based on genetic algorithm (GA) according to the user's marking. GA-based optimum design model is applied to the selection of display information for the flood control of the Amagase dam reservoir for verification of the proposed theory.

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In the present study, fuzzy logic control and genetic algorithms are applied to achieve advanced pump operation in combined sewer systems. Pumping rates are determined by fuzzy inference and fuzzy control rules corresponding to input variables. Genetic algorithms are used to automatically improve the fuzzy control rules through the genetic procedures of selection, crossover, and mutation. The effects of different fitness functions and learning conditions are investigated using a stormwater runoff model.
Conclusively, it is found that current pump operation can be improved by adding sewer water quality to the input variables and the fitness function; the improved operation can reduce not only floods in the drainage area but also pollutant loads discharged to the receiving waters.

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The aim of this study is to develop an estimation method of the plan for local disaster preparedness. To achieve this purpose, a computer simulation model of communication processes among the public agencies is developed according to the local disaster preparedness plan. Each agency is modeled as an object which is activated by disaster information and send the new information based on its task. The task of each public agencies is expressed in a rule format based on the provision of the plan. Then communication network among the public agencies under the disaster situation is simulated to analyze the performance of local disaster preparedness plan.

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Nature-friendly river works have been intensively executed since the announcement by the River Bureau in 1990 paying much attention to riverine ecosystems. Biological diversity is also discussed in river improvement works since 1992.
In this paper additional costs of nature-friendly river works, augmentation of conservation flow and selfpurification facilities by vegetation are investigated inductively. Benefit of nature conservation is estimated by a contingent value method, namely, willingness to pay. In the Tone River watershed it is concluded the benefit of nature conservation is larger than the cost of restoration works discussed in this paper.

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Big and rapid rivers in Toyama plain gave great benefits to people living there, whereas they destroyed the lives of people, rice fields and wooden houses which were financial infrastructures in Kaga province. The history of the farmers living there was that of the flood controls.
The most necessary structures for maintaining river embankments were bamboo cylinders which reduced the energy of floods. In this paper, the history was discussed how people in Toyama plain in feudal period controlled floods using bamboo cylinders made of stones and bamboos. It was also discussed that the combination of stones and bamboos was nature-oriented.

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The Hanaguri channel is known as mysterious-shaped structures, which was constructed in the Nakasu mountain to irrigate a paddy field lying in the middle reach of the Shira river basin by Kiyomasa Katou in 1608.
In this study, a field investigation and a model experiment were carried out to grasp the actual status and hydraulic functions of the Hanaguri channel. The results showed that the Hanaguri channel had 26 walls with a semicircular hole which was dug in the lower part of the wall, and the flow between the walls exhibited the characteristics of wall jet and had enough tractive force to transport volcanic ashes erupted from the Mt. Aso.

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In recent years, various landscapes design and evaluation of landscapes in river space have been tried. But, they depend on intuition and feeling generally, and they are not quantitative. Therefore, the Analytic Hierarchy Process (AHP) is noted settling the problem. AHP is conceived by T. L. Saaty for trying to find the greatest common measure to make a judgment. AHP obeys the following, constructing hierarchy, making a pairwise comparison, deciding weight, calculating the consistency index, deciding synthetic weight.
This study singled quantitative evaluation of river landscapes using AHP. It was concluded that this method is very useful.

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When designing the river environments, it is very important to analyze the aesthetic influence on each element composing riverine landscape. In this paper, the riverine landscape evaluation system was proposed through two stages of analysis. In the first stage, 30 persons as an observer group rated the riverine scenery for projected color slides which were taken at representative 30 points. The preference judging of observers were analyzed by the semantic-differential method for all of the presented slides. Using the multivariate technique, we characterized four categories as dominant factors for scenic preferences in principal component analysis. In the second stage, the landscape elements items and the score of scenic preferences obtained by the factor analysis were input to the neural network as initial data. Then relationship between those items and stores were characterized by sensitivity analysis of the neural network. The riverine landscape evaluating system was developed using the artificial neural network.

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