Experiments concerning failure of embankments due to overflow have been carried out to investigate the processes and to assess effects of slope protection, constructing models of embankments. The results revealed two distinct processes, creation of an erosional scarp (the embankment from which the downstream slope is removed due to erosion) after erosion of the downstream slope and upstream or upward advance of the scarp. The downstream slope was eroded quickly, while the scarp migrated upward slowly. The theory of the scarp migration in breaching due to overflow was developed, considering erosion of the nearly vertical surface of a scarp and mechanical stability of the top end of the scarp. The mechanism of scarp migration plays an important role in assessing the effects of slope protection. The theory allows the profile of a scarp to be determined under the condition of imposed parameters. In the light of the mechanism, two types of slope protection against breaching were assessed.

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This paper examines the relationship between physical, chemical and mechanical properties and desiccation of dredged sludge. The characteristics of the dredged sludge with high water content can be improved with various methods, i. e., solidification with stabilizer materials, mechanical dehydration, desiccation and heat stabilization. The consistency test, the pH test, the XRF analysis, the XRD test, the consolidation test, the permeability test and the fallcone test are herein carried out to identify the effect of the desiccation. The concluding remarks are as follows: 1) the liquid limit and compressibility of the sludge were dramatically reduced, while the permeability was increased with the desiccation; 2) the reduction rate of the compression indices of the original wet and desiccated materials was proportional with the ignition loss of the materials; 3) the desiccation of the dredged sludge reduces the amount of stabilizer required to obtain the specific strength.

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It is evident that the oil-palm wastes and its product, such as, the ashes obtained after burning the oil-palm fi bers and oil-palm kernel shells are becoming a serious environmental problem, especially, in Malaysia and tropical region in the globe. These ashes, which are not only thrown away without any commercial return but also a huge amount of money is being spent for its disposal, have been investigated in the production of concrete. This paper highlights some test results on the performance behavior of concrete incorporating palm oil fuel ash (POFA) as a partial replacement of ordinary Portland cement (OPC). It is demonstrated that the use of POFA in concrete not only improved workability but also reduced bleeding significantly. Result on compressive strength reveals that it has been possible to replace cement by 30% POFA without any loss of strength. Along with strength, some durability performance data of concrete in aggressive chemical environments are also presented and discussed. It was observed that the concrete with POFA exhibited better resistance against acid, sulphate and chloride attacks at all periods of immersion than the concrete with OPC. Experimental investigations, based on short and long-term study suggest that palm oil fuel ash can suitably be used as a prospective cement replacement material in concrete construction.

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Sustainable food production in arid areas is limited by scarcity of good quality water for irrigation. Poor quality water, including saline water, is therefore increasingly being used for irrigation in these areas, with its adverse effect on crop growth and soil properties. For establishment of sustainable arid land agriculture with saline water, we evaluated two methods of subsurface irrigation using porous rubber pipes from which water seeps out under hydraulic pressure. In one method, two pipes at 20cm interval were laid at 5cm depth (1D), while in the other method, one pipe was laid at 5cm depth and the other pipe at 20 cm depth (2D). The experiment was conducted on dune sand with soybean using saline water (3000ppm Na Cl). Growth and water use efficiency of soybean and salt distribution and balance in the soil were studied. Plant growth and water use efficiency of soybean were higher with 2D than with 1D at the end of the experiment Salt was accumulated at soil surface regardless of the treatment, however, the salt amounts did not increase below the 5cm depth between the irrigation pipes in 2D treatment Therefore, when irrigation water is saline, 2D is better than 1D for soybean growth and efficient water use in later growth season. Results suggest that the 2D could be better to control the soil salinity condition.

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This study was conducted to investigate water and solute transport during a winter to snow melt term at a thick snow region of an Andisol. Solution of potassium bromide was sprayed as a tracer at a beginning of the winter to a fi eld where onion had been harvested in autumn. The soil was relatively dry during the winter due to surface soil freezing and internal drainage. Soil became wet and water flow bypassing soil matrix occurred in the subsoil during the snow melt term. Leaching depth of bromide ion (Br) was longer than infiltration length of water calculated by piston flow model during the early stage of the snow melt term and the leaching depth of Br was shorter than the infiltration length during the latter stage of the snow melt term. Amount of water entered the soil surface during the winter to snow melt term was equivalent to the pore space of the soil to a depth of 1m. However, Bf was not leached out completely and 32% of Bf remained in the soil shallower than 1m. Amount of nitrate nitrogen leached from 1m-soil was 198kg N ha^-1 which must be larger than nitrogen uptake by onion plant.

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The aim of this research was to establish a basic structure of distributed hydrological model equipped with an ET sub-model which can be applied to watersheds having distinct dry season. The model is a grid-based model and each cell of the grid consists of two layers of storage tanks. The upper layer tank was considered to correspond to the root zone model, and the idea of Sakai's ET sub-model was employed to it. The main processes of this model such as infiltration, evapotranspiration, percolation, overland flow, interflow and channel flow were modeled by Green-Ampt explicit scheme, Sakai's ET equation, Brook-Corey equation, kinematic wave explicit scheme, Darcy equation and Muskingum-Cunge equation respectively. The model was applied to the Upper Prek Thnot River watershed in Cambodia. The model parameters were derived from a digital elevation model (DEM), land use and soil type map of the watershed. These parameters and the observed daily hydro-meteorological data (2001-2003) were used to simulate outflow hydrograph and to test the performance of the model. It was found that actual evapotranspiration was properly simulated in comparison with the potential evapotranspiration and the simulated daily runoff showed fairly good agreement with the observed runoff at Peam Khley gauging station. It was confirmed that this model could work properly with the ET sub-model.

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Water flow and solute transport through undisturbed Andisols in Kumamoto, Japan, having aggregated soil structure were investigated on the basis of solute dispersivity, λ, for saturated and unsaturated flow conditions. The dispersivities, λ, for the saturated undisturbed soil were considerably greater than for the disturbed soil, ranging from approximately 3 cm for the surface soil column (25-55 cm depth) to 38 cm for the sublayer soil column (60-90cm depth). The λ increased with the travel distance from 2 cm to the maximum value for the sublayer column because of preferential bypass flow through narrow pore space. On the other hand, the scale dependency did not appear for the surface column. Since plant roots distributed uniformly in the surface soil, solutes mixed well laterally in the surface column, resulting in the relatively constant dispersivity with the travel distance. The λ, for unsaturated conditions was sufficiently lower (< 1.4cm) than for saturated conditions. Furthermore, the difference between the surface and sublayer columns became small. As water content decreased, macropore flow could no longer be dominant and solute transport became uniform in the undisturbed column. Hence, the λ for the undisturbed soil became close to those for the disturbed soil for unsaturated flow conditions.

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A new method was proposed for hydraulic analysis and designing a multiple outlets such as sprinkler irrigation system. Pressure head H and velocity of the flow V at inlets of each lateral in the system are determined by relationship expressed by function H=f (V) . Supposing that valves are mounted at inlets of each lateral, using unsteady flow approach with downstream boundary conditions at valves identifffied by the above function, values of pressure head and velocity at inlets of each lateral will be rapidly and easily determined. With obtained results, pressure head and discharge of the flow at each sprinkler on each lateral will be also determined by forward step method. A flow chart for calculation on a personal computer was included. Our results show that using this method, we can analyze and design any complex sprinklers, micro-sprinkler and drip irrigation system. In addition, the calculation procedure is simple and results are accurate and fast.

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The defect in the concrete structure can be detected by using the resonant frequency of elastic wave measured by impact acoustic method. The resonant frequency is, however, dependent on the water content of concrete. To investigate the effect of water content on the resonant frequency, the deflective and longitudinal resonant frequencies were measured for the concrete having the various water contents in the laboratory. It was found as a result that the deflective resonant frequency reduced by 2-4 % for 1% reduction of water content, and the longitudinal one reduced by 1-2%. Moreover, the dependency of the resonant frequency on the water content was different between drying and seeping processes. The longitudinal wave velocity could be modeled by geometric mean for drying process and by harmonic mean for seeping process. Therefore, it was inferred that the zone near surface of the concrete, which had high water content at the seeping process, had a low elastic wave velocity and the resonant frequency became low as a consequent.

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Irrigation experiments on evergreen sedum of Kirinsou were conducted on sloped bed soil in glasshouse. The study was done during summer time. The result can be concluded as follow: 1) Evapotranspiration ratio of Kirinsou was decreasing after irrigation with lapsed day and pF values of the end of the irrigation intervals where ranging between 4.2 to 6.0. However, this ratio increased again at the beginning of each irrigation and Kirinsou plant recovered to the normal growth. 2) Cumulative value of evapotranspiration ratios with square root of elapsed time are forming a good fi t of quadratic curve with correlation coefficient of more than 0.99. 3) Evapotranspiration was affected negatively with soil pF value in which this relationship was passing through three different phases. In first phase, the evapotranspiration was influenced by LAI. In second phase, the evapotranspiration decreased shapely. Whereas, in the third phase, the evapotranspiration was decreasing gradually and gave values of less than 0.1. 4) The stress periods, when soil pF values were over than starting point of the third phase, were correlated negatively with dry shoot weight and LAI of Kirinsou. It suggests that the point of depletion for moisture content of normal growth in Kirinsou is pF4.2.

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A laboratory test method was investigated which will be used to evaluate the deterioration of rockfill materials, and thus, enable rockfill dams to be maintained over the long term. The degree of deterioration was represented by a comparison between the values of compressive yield stress for the original material and for the damaged material, measured in one-dimensional compression tests. The durability against crush was represented as the function of rockfill materials to be maintained. In this investigation, artificially-damaged materials were made from some gathered original materials and used as a substitute for naturally-damaged materials. To verify the validity of the method, tests were carried out for sa dstone and mudstone, whose levels of durability at the dam sites showed obvious differences. From the test esults, it was concluded that the compressive yield stress is an appropreate value for representing the degree of deterioration of rockfill materials, and that two practical usages can be proposed for this value, i.e., to judge the present degree of deterioration and to estimate the durability of the materials in the future.

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Paddy fields are frequently expected to act as sediment ponds that will counteract the red soil runoff. We observed the suspended sediment budget of paddy fields in six rainfall-runoff events on Ishigaki Island in southwestern Japan. The following facts were noted. 1) Suspended sediment runoff from the paddy fields continued for 6 hours or more after rainfall; 2) a relatively large fraction (soil particle size of around 0.1mm) in turbid water flowing into the paddy fields was deposited there; 3) the abundant fine fraction (soil particle size of around 0.03mm) become newly suspended in the paddy fields and was then discharged; 4) the paddy fields acted as a source of suspended sediment, not as a sink; and 5) the net suspended sediment load tended to increase with increased rainfall.

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This paper aims to statistically analyze the influence of nonfarmers' socioeconomic characteristics on their participation in maintenance activities for agricultural canals that harmonize with the ecological system. The study involves two hundred and twenty-one nonfarmers living in the central area of T town, which is classified as a flat agricultural area, in Miyagi prefecture. These nonfarmers participated in the maintenance activities of agricultural canals that did not harmonize with the ecological system. After analyzing the data using an ordered probit model and a binary probit model, the following results are obtained. In order to strengthen nonfarmers' participation in activities for the agricultural canal that harmonizes with the ecological system, it will be important to disseminate information about agriculture around themselves to them, to induced them to participate once in an easy maintenance activity, and to increase their interest in multifunctional roles of and problems related to the agricultural canal or provide them with the opportunity to directly use the agricultural canal.

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To evaluate economically multi-functional roles of the Yasugawa agricultural water by a contingent valuation method (CVM), mean values per household of willingness to pay (WTP) were estimated from the Turnbull scheme and with the Weibull distribution, and were 4, 352 yen and 4, 096 yen, respectively. Each functional role was evaluated economically using the combined index of its usefulness and importance, and functions of flood control, ecological preservation and water quality preservation were evaluated highly. The values of WTP allotted to their functions were 1, 262 yen, 827 yen and 1, 001 yen, respectively. From the analysis of collected questionnaires, was obtained the result that the practical function of flood control was evaluated highly at present, but the functional improvement of water quality reservation was expected in future. Many difficulties are involved in the distribution and the collection of questionnaires. Therefore, a linear relationship between the mean value of WTP estimated from the Turnbull scheme and the rate of non-farm household was presented to reduce those difficulties. Data investigated and obtained in 4 agricultural irrigation districts were used. The relationship could be applied to other agricultural irrigation districts adjacent to these 4 ones to estimate the rough value of WTP.

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Cracks generated in RC structure, especially served under the chloride-attack condition, promote the rapid reinforcement corrosion and lead to be dangerous in structural safety. The influence on existence and width of cracks to reinforcement corrosion concerned to chloride attack was investigated focusing to the cast-in-place RC structures served for long period as agricultural hydraulic facility. Intruded chloride ion concentrations showed different tendency due to the environmental condition, i.e., exposed to air or under the water. Slight reinforcement corrosion was confirmed even though there were no cracks and assured the cover thickness of reinforcement, however, most of them wasn't harmful corrosion. In case when the crack was generated in structure, degree of reinforcement corrosion was affected to the type of reinforcement, it was suggested that deformed bar was effective on durability of RC structure. The progress of reinforcement corrosion was influenced to not only the direction but also the locational relations of both crack and reinforcement. Chloride attack condition was so severe for RC structure, therefore, it was dangerous to utilize the allowable crack width configured for normal environment, necessary to configure the intrinsic crack width for chloride attack environment.

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The increasing use of drip and sprinkler irrigation system have shown that applycation of fertilizer are desirable to along with irrigation water. In agricultural facilities, low cost and low energy are requested to reduce production cost of agriculture. When the water passes through a pipe bend in irrigation system, by the centrifugal force of the flowing water, the water pressure of the outside of curved pipe is higher than that of the inside. If the inside and outside of the curved pipe are connected by the pipe, the bypass flow is generated in this route. If the fertilizer tank is connected in the bypass route, the fetilizer is injected automatically in irrigation system without additional energy.
In this paper, the hydrulic design procedure of chemical injection system in irrigation facility by thr use of pipe bend was shown. The characterristis of byppas flow in bend pipe was shown. By the increasing of bypass flow rate, the pressure differrence between inside and outside in curved pipe is greatly reduce. This point is the defect of application of curved pipe in chemical injection system by the use of pipe bend. The increase method of bypass flow wasproposed and effect of this method was shown by the use of chracteristics of centrifugal force line. The design procedure of chemical injection system was also shown.

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Many irrigation tanks need their rehabilitation urgently, because they are centuries-old. This paper is associated with excess leakage of impounded water through an earthen embankment. An attempt to identify leaky embankment transactions using the result of field investigation, to decide the rehabilitation method and to estimate the permeability of the improved embankment is made for an overage tank in Ehime prefecture, Japan.
There seems to be a highly permeable layer between F.W.L. and W.L.-5.0m in the embankment judging from the in-situ up-to-date data and the hydro-geological data. And, the identification enabled the small scale improvement work, namely, the embankment of 10.0m depth from the crown was excavated and replaced by the impermeable soil. Further, the electrical resistivity surveying was carried out and the validity of the rehabilitation work was demonstrated by comparing between the results of the improved zone and the original zone.

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The amplitude of tides in the Ariake Sea and surrounding area has been decreasing since mid-1980s. However, the amplification of M2 constituent at the Oura Tide Gage Station to the Kuchinotsu Tide Gage Station increased betweenearly-1970s and mid-1980s and then decreased. The Isahaya Reclamation Project and changes in sea surface elevation were considered to be the factors contributing to this change. Much effort has been spent on quantify the effects using numerical models. However, the increase in tidal ranges between early 1970s and mid-1980s could not be consistently correlated with these factors: the results varied between analyses depending on the numerical model used. On the other hand, the patterns of change in the tidal current could not be clarified because of an absence of reliable field data. Therefore, numerical model simulations and hydraulic model experiments have been conducted to quantify the effect of the following factors: the Isahaya Reclamation Project, seaweed cultivation and the new Kumamoto Port. Yet from these efforts, the extent and degree of the influence of these factors have not been clarified. Development of a fine mesh model, which can simulate the tidal change and a 3D-current with high accuracy based on highly accurate tidal current survey, is therefore recommended.

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