A one-dimensional model for an open channel flow with submerged vegetation along the channel side was constructed for a natural open channel. A three-dimensional flow could be treated as a two-dimensional one by using the Manning roughness coefficient including the influence of the submerged vegetation. The energy loss was calculated by a new model using the equilibrium equations of energy as a function of the averaged velocity in each area. The averaged velocity was calculated using a velocity ratio and a continuous equation. The one-dimensional water surface profile was calculated by the law of conservation of energy using the new energy loss model. This result was compared with the experimental value and with the result obtained using a previous analysis model. It was found that the model proposed in this study coincided more closely with the experimental value than the previous analysis model.

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An anionic surfactant is used in detergents. It has also been tested as a cleaner for soils contaminated with hazardous organic compounds. However, surfactants contaminate aquatic environments because they can destroy cell membranes. Surfactant movements and reactions in soils are not well understood. In this study, we performed surfactant transport and adsorption experiments in soil in order to clarify these phenomena. A linear anionic surfactant, sodium dodecyl sulfate (SDS), and a highly humic volcanic ash soil were used. SDS transport and adsorption showed characteristic phenomena. with the results indicating that SDS is adsorbed cooperatively by the humic substances in the soil. These results were completely different from those for simple anions such as nitrate and chloride. Under a critical micelle concentration, the decrease in the SDS breakthrough curve coincided with the decrease in hydraulic conductivity, demonstrating that SDS adsorption generates a decrease in hydraulic conductivity.

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One of the representative algorithms for learning of an artificial neural networks (ANN) is the back propagation method. But, it is sometimes difficult to converge and learn efficiently, because it minimizes the error function of the outputs for each learning data set in order and not simultaneously. In order to minimize the error functions for all learning data sets simultaneously, a new learning algorithm is proposed using the extended Bayesian method. However, a dificult but important problem in this method is to determine optimally the number of hidden layer units L_m for ANN and the parameter λ² for the extended Bayesian method. Thus, the determination method of optimal λ² and L_m by Akaike Bayesian information criteria is proposed. As a result of having applied it to consolidation and seismic problems, it is comparatively clear that the proposed method has faster convergence and higher learning capability.

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We measured the coefficient of roughness in a hydraulic experiment using a concrete channel whose surface was treated to simulate abraded concrete. Various surface roughness parameters were trialed to determine those that best represent the surface roughness of the experimental concrete panels. The calculated coefficient of roughness (n) was 0.013. This value is within the range of the design standards for concrete channels. The height distribution of the surface of the experimental channel was characterized by skewness that showed bias of the height distribution of the roughness. The equivalent roughness of the simulated abraded concrete channel can be expressed as k_s = 2 × R_a for R_a of 0.5 ± 0.12 mm or k_s = 0.26 × R_z for R_z of 4 ± 1.43 mm.

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In Okinawa Prefecture a problem concerning the outflow of red soil has surfaced whereby red soil flowing out from farmlands is deposited in settling basins. The current concern is to prevent this deposited red soil from flowing out of the basins. In treating this deposited red soil, it is necessary to take into consideration the creation of a recycling-based society and the effective use of local resources from the viewpoint of social technology. In a pilot area in the main island of Okinawa, a drainage test was conducted and the natural drying of the deposited red soil was simulated using technologies based on farmland engineering and hydraulics. The objective of this test was to study a red soil recycling system for the reuse and restoration of the deposited red soil. In the drainage test conducted using an underdrain within the settling basin, water could be drained out of the pilot area without high turbidity. A drying test conducted after the drainage demonstrated that a deposit 10 cm deep required 2.5-6 days for effective drying if the daily evaporation was 3-7 mm. The most appropriate period for the drainage and drying of the deposit was October to November, if the weather conditions and work environment of this region were taken into consideration.

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In this study, we estimated the new available moisture on Sedum (Kirinsou) from an experiment using pots for measuring the amount of transpiration in a growth chamber under two different conditions, optimum and high temperature. The results are as follow; 1) Transpiration was confirmed during the dark period under both conditions, although the transpiration ratio in the optimum temperature condition was higher than the hot condition. 2) The relationship between the cumulative daily transpiration ratio and elapsed time fit secondary and logarithm functions precisely. 3) The activity of transpiration was confirmed under the condition of soil moisture less than pF4.2, with the water held in the plant contributing to this transpiration 4) Considering the total available moisture including with water in the plant can help save the amount of irrigation water needed better than considering soil moisture alone.

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The influence of land use on river water quality was examined by conducting water quality surveys at 18 rivers in the Abashiri River basin flowing through agricultural land in the autumn, 2005. Previous studies have shown a correlation between NO_3-N concentration in river water and the upland field and grassland field ratio, and they have found that NO_3-N concentration is influenced by the amount of excess nitrogen from cultivated land. In the studied area, a high correlation was observed between NO_3-N concentration and upland field and grassland field ratio. In the Abashiri River basin, NO_3-N pollution in river water is influenced by the amount of excess nitrogen from cultivated land.
The influence of water quality in tributaries of the Abashiri River on eutrophication in Lake Abashiri was studied, by comparing the N/P ratio in those tributaries to the N/P ratio of the Abashiri River and to that of Lake Abashiri. A high correlation between N/P ratio and upland field and grassland field ratio was observed. In basins of tributaries where the upland field and grassland field ratio exceeds 30%, the N/P ratio is higher than that in the Abashiri River and that in Lake Abashiri. From this result, the eutrophication of Lake Abashiri is attributed to the load in river water from tributaries whose the upland field and grassland field ratio exceeds 30%.

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To perform function maintenance of irrigation canals, it is necessary and indispensable to execute overall function diagnosis and performance design for hydraulics and water serviceability in addition to the former structural function, and also necessary to set function maintenance measures. This report takes up the problem of declined hydraulic performance caused by explosively increased algae in irrigation canals in a paddy field irrigation district. The area where water overflows from the sidewall of an irrigation canal when algae grows thickly in large quantities is hypothesized by a hydraulic performance check method using non-uniform flow calculation. Therefore, 5 schemes for the overflow stream measures have been prepared. The optimal scheme is selected based on the calculation of life-cycle cost taking maintenance into consideration.

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For this study, we applied data of ALOSIPALSAR, L-band Synthetic Aperture Radar (SAR), to analysis of a peatland site, Sarobetsu Mire, Hokkaido, where environmental rehabilitation has been attempted. Using data of 10 scenes that were taken during spring to fall in 2006-2007, we analyzed the relationship of the backscatter coefficient to various factors related to soil, hydrology, vegetation, and geography.
Results of regression analyses with single factors clarified significant relationships for factors including dry bulk density, the rate of nitrogen content, the C/N ratio, the vegetation proportion, and NDVI, revealing the characteristics about scattering and incident angle that are considered peculiar to peatlands. Furthermore, the result of multiple linear regression analysis revealed that the dry bulk density of the surface soil was the dominant contributing factor, enabling construction of a multiple linear regression model, which is significant for estimating the spatial distribution that is peculiar to the peatland surface soil using L-band SAR.

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