For the domestic food transport the choice of the most fuel-saving route was treated as a problem of the choice of the minimum distance route between destinations. However, in a country like Japan where its territory is occupied by steep landscape, road inclination has significant influence on fuel consumption of vehicles. Therefore we firstly quantified the relation between road inclination and fuel consumption of a car. Then using this relation, we developed an algorithm that can extract most suitable route under conditions of minimum distance, minimum fuel consumption and minimum travel time. Then by comparing nature of extracted routes in six prefectures in Kinki Region, we examined the effect of road inclination on the choice of the most fuel-saving route. Analysis showed that “minimum distance” is not a consistent indicator of fuel consumption when applied to regions of different relief. Minimum distance did not always result in minimum fuel consumption. Local relief and degree of road improvement in the region (national routes and highways) had significant influence on fuel consumption of the vehicle.

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We propose a method to distinguish the land cover of paddy fields with high resolution satellite data. The method is a combination of image classification and visual interpretation. First, pixel-based image classification of land cover is performed using a supervised classification method. Next, land cover of paddy fields is distinguished by overlaying the resulting images with parcel boundary data of paddy fields, and consolidating the classification results for each parcel (that is, extracting the class with the majority of classified pixels in each parcel). Last, confirmation and corrections of the primary distinction results of all paddy fields is performed by visual interpretation of the satellite image. We distinguished land cover of paddy fields in flat paddy field areas using WorldView-2 satellite data (8-band pan-sharpened image with a resolution of 50 cm) by the proposed method, and verified the distinction accuracy using on-site survey data of paddy field land cover. In the distinction using satellite data acquired on July 21, the number of parcels where land cover was correctly distinguished for 1,527 parcels was 1,517 with a distinction accuracy of 99.3%. In the distinction using satellite data acquired on August 23, the number of parcels where land cover was correctly distinguished for 1,158 parcels was 1,143 with a distinction accuracy of 98.7%.

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In order to figure out the rainfall-runoff mechanism and evaluate the flood mitigation capacity of dry terrace field, we measured precipitation, discharge and groundwater table in a dry terrace field catchment in Choshi city, Chiba. Surface runoff was generated by excess of infiltration capacity when peak precipitation intensity was over 8 mm·(10 min)^-1. Unless the surface runoff was generated, the peak specific discharge was reduced to 8-39% of the peak precipitation intensity. The groundwater table at the upper terrace rose 2-3 times a year, on the other hand, the groundwater table at the lower terrace rose up to the surface several times a year. Finally, we created Tank model, which represents the characteristic of discharge in the catchment, and we evaluated the flood mitigation capacity of this field by the infiltration capacity and the peak relaxation time “τ₅₀”. The τ₅₀ of this dry terrace field was 6.4 h, and this value was larger than 5.1 h in the irrigated paddy field and smaller than 8.4 h in the non-irrigated paddy field in Tsukubamirai city, Ibaraki.

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In this paper, we describe the development of an inundation process model integrated with a basin-scale distributed hydrological model. The procedure applied for assessing the flood hazard uses a simple assumption that an inundated area is a reservoir, in which the water levels for the river and the surrounding reservoirs are equivalent. Inundated water levels were calculated with continuous equations of the reservoir with H-V and H-A relations in the area, in which the excess rate of surface flow above the maximum conveyance capacity of rivers is treated as an input to the inundated areas. To apply this inundation model, we used Aster GDEM, which is one of high-resolution digital elevation models to extract detailed topographical features. We applied the model to the Xebanfai River in the Laos PDR and carried out daily calculations for 5 years. By incorporating the inundation process model, the performance of the distributed water circulation model were improved in terms of calculated discharges showed that the peak discharges and their timing of occurrence. In addition, we rigorously validated the model by comparing the calculated inundation areas with those extracted from the ALOS/PALSAR images. The comparison revealed that the large-scale inundation processes in the lower reaches of the basin were precisely represented by the model, but also showed that additional analyses are required to improve the accuracy in the middle reaches and branches.

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Thus far, the focus of studies on seepage failure, known as sand boiling or the piping phenomenon, has been to determine the critical hydraulic gradient or the critical seepage flow velocity. However, the transport of soil after seepage failure also needs to be well investigated in order to estimate the damage to soil structures or the ground. This study has experimentally investigated the behavior of sand and seepage water during sand boiling induced by upward seepage flow. In the experiments, the discharge of sand particles and seepage water were measured separately during sand boiling, and their migration velocities were obtained with the measurement of the hydraulic gradient. The results have revealed that the equilibrium of the forces exerted on the sand particles, i.e., gravity, buoyancy and fluid-particle interaction, can be used to estimate the velocity of the sand particles subjected to upward seepage flow regardless of the sand type.

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We evaluated the capabilities of the intermittently loaded vertical flow constructed wetland (“VF wetland”) set in the planted canal circulation water as an oxidation system. Results show oxidation performance in the filter media with following properties. The water flow velocity was about 5-15L·s^-1·m^-2, CEC was more than 20cmol·kg^-1,  and NO₂-N concentration rose during one week to one month from filter media installation. Subsequently, the following process was carried out in 45min for a self-priming siphon operating cycle. NH₄-N was adsorbed to the filter media, with nitrification by nitrifying bacteria, and leaching from the filter media. Nitrogen removal by denitrification that progresses by nitrification by intermittent loaded vertical flow wetlands, and treated water circulated to the inlet of the planted canal. VF wetlands using suitable filter media can function as an effective energy-saving water purification oxidation system.

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This paper presents the parameter identification of an elasto-plastic constitutive model for geomaterials and a risk evaluation for neighboring work based on a data assimilation using the particle filter (PF) and incorporating a soil-water coupled finite element analysis with an elasto-plastic model.  After the numerical implementation of input data for the soil-water coupled FEM is examined, based on an in situ investigation, its applicability to an actual excavation work is discussed.  A risk assessment for an alternative design, using the probability density which the PF computes and updates on the basis of observations, is also proposed.  It is revealed that, for a practical example, the FEM results using the parameters identified by PF show a good agreement with the observations and that a quantitative and reliable risk evaluation can be achieved using the proposed method.

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Physical meaning of the creep length calculated from the creep theory has been discussed on the stability analysis for seepage failure of foundations under weirs. It was indicated that these creep theories couldn't predict critical water head under weirs and the Terzaghi's method could predict seepage failure under weirs in previous studies. However, these previous studies were used Toyoura sand only as the ground material. In this study, seepage failure model experiments with two cases of weir shape were conducted. Three types of silica sands as the ground materials were demonstrated. Creep theory, Terzaghi's method and critical velocity methods were reexamined by these model experiments. These previous formulae couldn't express results of model experiments of large particle size of silica sand. Modified Terzaghi's method to model the influence of diameter of void was suggested in this study. It was observed that the modified Terzaghi's method predicted the results of model experiments well.

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The following 3 types of depths were created to investigate the effects on wintering fish in an agricultural canal: (1) a 30-cm-deep dammed section of the canal; (2) a 60-cm -deep hand-dug section of the canal that was covered; and (3) a 60-cm-deep hand-dug section of the canal that was left uncovered. The number of fish species, fish density and the diversity index were compared at each sampling station during the same months the previous year.
The 3 above-mentioned parameters showed increased values after the depths were created. Fish density in the covered 60-cm-deep section was higher than that in the 60-cm-deep section with no cover. Moreover, the fish marked previously in the mark and recapture method either remained at the same depth or moved from a depth with no cover to a covered depth. Therefore, the depth with a cover could be especially effective for fish wintering. Consequently, bank trees, overhead banks, and submerged plants should be conserved as a cover for wintering fish.

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In rural communities of Japan, an aging population and progress in mixed inhabitation have reduced the workforce available to maintain irrigation/drainage canals, so cooperation of non-farmers is desired. To promote the participation of non-farmers in maintenance activities, it is important to effectively raise the level of factors that influence non-farmer participation. Therefore, focusing on factors that raise the level of participation by external approaches, this study analyzed the structure of non-farmer participation (the relationship between non-farmer participation and factors that influence this relationship) in activities to maintain irrigation/drainage canals with a questionnaire given to 800 non-farmers and a Structure Equation Model. As a result, the following was determined: (1) participation in maintenance activities is influenced by both willingness to participate and ability to participate, (2) willingness to participate is influenced by factors such as awareness of the necessities for participation and (3) awareness of the necessities is influenced by knowledge of irrigation/drainage water. Fitness indexes of the structure were 0.901 for GFI, which is above an index of 0.9 indicating good fitness, and 0.052 for RMSEA, which is below an index of 0.08 indicating reasonable fitness. Therefore, we confirmed the structure was supported by actual data.

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