The sediment transport of river with agricultural watershed makes difficulties in water utilization, flood-control and maintenance of the environment. Suspended sediment has significant effect on wide areas. The transport of suspended sediment is discussed in this paper. The relationships between suspended sediment load and hydrogeography were examined by observing river water turbidity at three agricultural watersheds in Hokkaido.
Farmland percentage was found to be importantly affected by watersheds and riparian forest. Sediment transport was noted to be governed by changes in discharge zones.

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Recently in Japan, land consolidation projects are carried out by accumulating cultivation rights for the purpose of enlarging paddy field lots. Usually one field lot consists of many small-sized owner lots.
In these cases, it is feared that land owners will reject their lots to be substituted as lots of short frontage because they expect their lots to be converted to housing lots in the future. Moreover, this constraint of frontage of owner lots, it is also feared that field lots cannot be enlarged enough.
In order to clarify this constraint of frontage of owner lots, we investigated four study areas, that were the same in realizing large-sized paddy field lots by accumulating cultivation rights, but different in their potential of urbanization. Through this survey, we found many owner lots of short frontage in these areas that could not be used for housing lots individually. As a result, we showed that 1) in non-urbanized areas it is not necessary to substitute owner lots with frontage enough to be converted to housing lots individually, and 2) it is not necessary even in urbanized areas in the case where each owners cannot convert their lots to housing lots individually by geographical/ topographical conditions of the area.

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Concentrations of soil gases differ from those of atmosphere, because soil microorganisms and soil animals respire and gases diffuse through soil pores in proportion to the gradation of their concentrations. The objective of this paper is to make clear the correlation between the distribution of microorganisms and CO₂, O₂ gas concentrations in a field under rotating use.
Sail air, sampled by using gas sampling pipes, was analyzed by gas chromatography. The number of microorganisms was counted by dilute plating method. Although the profiles of the number of microorganisms changed little, CO₂ and O₂ gas concentrations in the soil air changed remarkably. The simulation of CO₂ gas concentrations by using Fick's law revealed that the respiration of microorganisms contributes to the construction of soil gas distribution. Relatively high CO₂ gas concentration in October was attributed to relatively high activity of microorganisms in this season due to the high soil moisture contents and relatively high temperature.

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The diurnal energy budget in a paddy field in summer is characterized by the Bowen ratio Bo which is small and drops often below 0 in the afternoon. Focusing on this phenomenon, the effects of meteorological conditions and vegetational factors, such as the growing stage and the canopy resistance r_c on the energy budgetin the paddy field, were assessed. First, the dependence of Bo on air temperature was discussed in terms of the growing stages and diurnal variations. Next, it was shown that r_c was not directly related to Bo. Therefore, the critical canopy resistance r_cc, which is defined as the canopy resistance when Bo=0, was applied to standardize r_c. It was demonstrated that r_c-r_cc was highly related to Bo. Finally, it was found that bulk stomatal response, interacting with meteorological conditions, had an effect on the diurnal Bo.

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What is the effect of stream sounds in channel landscape? Recently, many canals have been remodeled. to improve the environment in rural settlements in Japan. Almost all Japanese canals were designed only in terms of sight factors. However, stream sounds are a feast for our ears. For example, stream sounds are generally created in traditional Japanese gardens as a gardening technique.
In order to measure the influence of stream sounds on attractiveness of channel landscape, 6 types of waterways were selected and 3 types of sensory tests were carried out on 144 subjects. Almost all subjects appreciated stream sounds as an amenity. If environmental elements of waterways consist of visual and auditory factors, then the pleasantness of stream sounds can make channel landscape more attractive.

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We analyzed the consciousness structure of canal sound space and detected principal components and sound factors of sound image space. Sensory tests applying to 10 types of waterways were carried out on 84 subjects to gain a psychological image of stream sound. Psycholdgical image of stream sounds is made up of 2 elements, namely, loudness and melodious of sound. Next, sound physical analysis was implemented to quantify sound characteristics. Sound factors affecting loudness were sound level and sound factor affecting melodious were spectrum envelope. Stream sounds with a local maximum of sound pressure level covering the frequency range from 500 to 4000 Hz were judged by subjects as a high-pitched sound.

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The nitrification capacity of riffles in a natural river was discussed. The bacteria density in the river bank subsurface layer was estimated together with the seepage flow direction and speed, the porosity of the sand gravel layer and the nitrogen concentrations in the river and seepage waters. On the basis of the exponential growth model for nitrogen oxidation bacteria, the nitrification rate of the seepage layer on the river bank was obtained. The spatial variety of bacteria density due to the inhomogeneity of gradation structure, porosity and the input of ammonium and nitrite nitrogen was observed. Without the considerable load of substrate, the density of the ammonia oxidation bacteria per unit volume of the seepage layer was 0.5-1.5mg/L and that of nitrite oxidation bacteria was 0.05-0.2mg/L. The nitrification capacity in the subsurface layer of a riffle was estimated more than ten times as large as that of a pool in the same longitudinal length. The maximum density of the ammonium and nitrite oxidation bacteria was 5.35mg/L and 1.46mg/L respectively in the subsurface layer adjacent to the wastewater effluent, in which approximately 20% of the inorganic nitrogen load was thoroughly oxidized.

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Macropores influence the movement of water and air in the soil significantly. A study was conducted to investigate the characteristics to determine the water and air movement functions of tubular-pores which originated from plant roots. The results were as follows:
1. The smallest macropore had 50μ m diameter, where water drained at pF 1.8 from the viewpoint of soil pore structure.
2. Horizontal hydraulic conductivity was larger than vertical in most of the layers since large tubular-pores (diameter: 1-2 mm) were mainly in the horizontal direction. It was noted that large tubular-pores had high tortuosity and small tubular-pores (diameter: 50-300μm) connected with large pores.
3. It is suggested that there are some differences between the routes for water and air movement. The difference may be due to the complicated network of tubular-pores.
4. We can classify the soil samples to four types by the structure of entry pores which are estimated by the drainage curve from entry-pore experiment and radiographs using soft X-ray. Tubular-pores of varying diameter connect together to make the entry-pores in soil.

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In this research, an analytical condition necessary and sufficient to do the prediction of a realistic thermal crack in the RC box culvert was examined. The RC box culvert targeted by this research is actually constructed, and the thermal crack is generated in an early age. The examination items are the presence of autogenous shrinkage and drying shrinkage, the presence of the bond link on a ground and concrete boundary surface, and the presence of the bond link on all placing surface of concrete. An analytical condition to express the measured thermal crack well is a case to have considered both of autogenous shrinkage and drying shrinkage, and considered the bond link on a ground and concrete boundary surface. On the other hand, some consideration was done concerning the method of dividing the element in the direction of length of the culvert.

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The spatial distribution of the cropping units in rural area, which related to the nitrogen inputs and intakes, is examined using remote sensing data. The spatial patterns of the amounts of both nitrogen input and intake through crop production on farmlands are obtained. As a result, it could be clarified that the amount of annual nitiogen inputs (by chemical fertilizer and compost) that range between 60kg·ha^-1 and 325kg·ha^-1, is unevenly distributed. In addition, the amount of annual nitrogen intakes by crops (by-products is excluded) that range between 11kg·ha^-1 and 125kg·ha^-1, is also unevenly distributed. This indicates that the spatial distribution pattern of nutrients input and intake through agricultural activities should be examined to study a watershed environmental control and a regional agricultural management. Thus, it is considered that those spatial distribution patterns are effective to examine regional material recycling system and material flow for watershed environmental management.

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In this paper, the authors focus on the flotation mechanism of underground structures induced by liquefaction of the ground during/after an earthquake and the method of countermeasure designing for it. As for the flotation mechanism, it is guessed that the soils to the bottom of the structure from the circumference during floating were supplied. This guess is based on the assumption that the flotation occurred by the difference of effective pressure at the bottom of the structure and the ground around the bottom. As for the countermeasure method, it thought that floating could be delayed by installing a fin in the base part of the structure and interrupting this supply. This way of thinking was confirmed by shaking table tests performed respectively four times on the soils with buried structure case, no-countermeasure case, and the countermeasure case. Next, the establishment of an evaluation method of the safety against flotation is surely necessary in the design. In finite element analysis, it was examined through the simulation of shaking table tests if finite element analysis could be used as an evaluation of the safety against the flotation. As a result of this study, flotation is influenced by the difference in pressure, the proposed countermeasure method is effective and flotation can be reproduced by the analysis.

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The form and functions of the tubular macropores which are in volcanic ash subsoil of the Kanto Loam Formation (Tachikawa, Musashino and Shimosueyoshi Loam Formations) on the Musashino plateau, Tokyo, were investigated. The occurrence of the tubular macropores, their form and distribution in a downward direction were studied through basic physical properties and Soft X-ray radiographs. The results of this exhibited the following pattern of physical properties from upper to lower layers in the Kanto Loam Formations.
(1) An increase in dry density
(2) A decrease in saturated hydraulic conductivity
(3) A decrease in macropore numbers
(4) A change form of tubular macropores

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Large and small-scale laboratory tests were carried out to investigate compaction characteristics and permeability of soil containing large particles. The materials were tested containing different maximum particle sizes and gravel contents. Different gravel types were used to study weathering effect. Different sizes of test equipment were used for the compaction tests. Soil specimens were compacted under various compaction energies. Finite element analysis was used to predict permeability of soil containing large particles based on permeability of matrix soil alone. The results show that with an increase of gravel content, maximum dry density of soil increases up to gravel content of 60% and dry density of matrix fraction decreases especially when gravel content is over 40%. Even if at the same compaction energy heavier rammer produces higher maximum dry density and lower optimum moisture content. Within gravel content range of 20-40% for soil containing hard particles and 20-60 % for soil containing soft particles, permeability of earth-rock mixture is lower than that of matrix soil tested alone. Specimen containing larger maximum particle size attained lower permeability. Numerical study shows that permeability of soil containing large particle can be well predicted.

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This paper discusses the irrigation management in a cooperative farm in the Kzylorda region, Republic of Kazakhstan, of the Syrdarya delta in the Aral Sea, where paddy-based crop rotation is mainly carried out with alfalfa and wheat, such as 3 or 4 rice crops during 7 or 8 years. Water balance analysis revealed that water applied into paddy fields raises the ground water level to the extent that non-rice crops can withdraw the ground water, and that irrigation efficiency of the study area is considerably low as 30 to 45%. Four to six hundred million cubic meter of water could be saved in the left bank of the Kzylorda region by increasing irrigation efficiency through the implementation of land consolidation and infrastructure improvement. It is also clarified that the lack of agricultural machinery and their replacement parts is strict constraint to maintain the cropping area.

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Several series of installation tests for buried pipeline were performed to investigate the effectiveness of geogrids in enhancing the uplift resistance of buried pipes against uplift force by buoyancy. The tests were carried out using the pipe's diameter of 1100mm in model sand ground. In the tests, four kinds of uplift protection methods were installed around the buried pipe with shallow depth of soil cover. Consequently, it was revealed that the protection method with geogrid and gravel as backfill material increased the uplift resistance of buried pipes. Considering the least depth of soil cover of buried pipe, the incorporation of geogrid reinforcement can lead to a decrease to nearly 0.0m for shallow soil cover.

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A local rule for the particular type of CA model, e.g., CL-CA model, is developed to predict the behavior of granules during the shear. Several lattice sites of CA are connected as dodecagon polygons to consider the different size of particle and the packing of granules. Computed relocation of disks based on the proposed rule for the uplift problem of the trap-door is found under devastating reduction of computing time and is compared with experimental result in the two-dimensional trap-door test using aluminum rods. Numerical and experimental results demonstrate the validity of the proposed CA model and its local rule. Contact force distribution among particles is also calculated under the local rule and examined through the comparison with DEM simulation.

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The soil layer in an upland field of kuroboku soil is devided roughly into a surface soil layer and subsoil layer. The physical properties of soil are considerably different between them.
This study demonstrated that the differences in the thickness of the surface soil layer has influence on the quantitative variation, consumptive use and vertical movement of soil moisture in the several soil layers of vertically different depths. The writers gave particular attention to the variation of matric potential in comparatively deep soil layers. Soil layer depths of the examination ranged from the surface to 170 centimeters.
Two test plots of considerably different surface soil thickness were investigated comparatively and contrastively. As a result of this examination, it was clarified that the aspects of vertical movement and comsumptive use of soil moisture were considerably different depending on the disparity of boundary depth between an A-horizon and B-horizon.
This paper is the result of an examination, which was performed in a test field of continuous long-term yearly use of the three major nutrients of chemical fertilizers. This study was performed in the agricultural experimental field of Ikuta school of Meiji university, and the nature of the soil is Kanto loam soil layer.

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To investigate the effect of irrigation water onto the change of groundwater level in Dogo plain, a numerical experiment using a quasi 3-dimensional unconfined groundwater model was implemented. The distribution of groundwater level from Jan. 1^st 1993 to Dec. 31^st was simulated with observed or estimated time-dependent water levels in rivers and discharges from 47 wells for municipal and industrial waters. The irrigation water was taken into account in the manner that the water of 2 mm/d recharges the groundwater from paddy fields during 4 months irrigation period. Comparing the results with irrigation and without irrigation, the distribution of temporally and spatially changing increment of groundwater level caused by irrigation water was revealed. The results showed that the difference of groundwater level with irrigation water and without one is larger in the south-west region of Dogo plain and the difference becomes larger in drought year than rainy year.

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In the previous studies on the suspended sediment runoff of river, the relationships between suspended sediment concentration (C) and discharge (Q) have been classified based on the time lag between the peaks of C and of Q or the shapes of hysteresis loop of the C-Q curves. In this paper, the C-Q relations observed in some watersheds in Okinawa are classified according to the previous researches and the characteristics of _suspended sediment runoff is also discussed. As the result, the explanations for the suspended sediment runoff described in the previous studies can be applied well to the observed data. Moreover, observed examples show that simultaneous types in the classification based on time lag and counterclockwise types in the classification based on the shape of C-Q curves are predominant in comparison with previous studies. This result means that the observed data in Okinawa indicate the characteristics of the erosive watersheds.

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[in Japanese]

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