In order to investigate the statistical and hydrological characteristics of rainfall in mountainous basins, we have installed a series of tipping bucket type-raingauges along the slopes of Mt. Yubari in the center of Hokkaido, Mt. Gozaisho in Suzuka Mountains and Owase in Mie prefecture, and the observations of rainfall were carried out from August to October, 1988-4993. From the observation, we could obtain rainfall intensity R(mm/min, mm/h, mm/day) for various observation time and total rainfall amount P(mm) for each rainfall events. The following knowledges concerning with rainfall characteristics in mountainous basins are obtained. (1) In Mountainous basins, total rainfall amount observed at each gauge sites increases linearly with their elevation, and its gradient also increases linearly with rainfall intensity (amount). (2) The relation between the total rainfall amount P(mm) and duration of a rainfall event D(hour) shows P∝Dⁿ, n=0.3-0.8, and the relation between the maximum rainfall intensity R_max(mm/h) and various observation time T(5-60 minutes) also shows R∝ T^-m, m=0.2 or 0.5, which depend on meteorological classification of rainfall types (stratiform or convective). The exponents, n and m are different from the meteorological types of rainfall (typhoon, front and sunder storm). (3) We could obtain the expression to estimate the basin-averaged rainfall amount P, which shows 10-80% larger than the amount observed at the foot of the mountain.

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Flow parameters introduced in the authors' previous model on the head of the gravity currents which govern the variations of flow depth, density and velocity of the head of the currents have been examined for the inclined plume and thermal. These parameters are entrainment coefficient, E, and expansion coefficient, m, which indicates the growth rate of flow depth due to the sum of entrainment and streamwise convergence of the depth averaged velocity. As the results of examination, the values of m showed no significant difference between these flows when bottom slope and width enlarging rate are set at almost the same values for both flows. The value of E, however, showed significant difference between these flows. The E/m value of a thermal is greater than unity, while that of plume is a little smaller than unity. This expresses the fundamental difference between these two types of flow. The above mentioned model explains well the difference between the properties of both density and velocity variations of the heads of plume and thermal.

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A numerical analysis has been performed for developing turbulent flow in a trapezoidal open channel flow by using Reynolds stress model. Govering equations are transformed from the physical plane to the calculation plane by boundary-fitted coordinate systems. The calculated results are compared with the experimental data available. As a result of this examination, it made clear that the present method was able to predict well cellular secondary currents near the free surface, which were induced by anisotropy turbulence, and the experimental results of Reynolds stresses without a great discrepancy.

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This paper present a new approximate calculation method for three-dimensional nonlinear interactions between Stokes waves and submerged coastal structures. In the mathematical formulation, Green's Identity formula is used to express the distributions of the velocity potential on a horizontal plane, and a collocation method of matched eigenfunction expansions is also utilized to derive the linear relationships for the velocity potential and its normal derivative on the adjacent fluid region. The particular solution of the second-order boundary value problem, which satisfies the nonhomogeneous free surface boundary condition, is approximately expressed on the assumption that it has the same form of an eigenfunction in the vertical direction as that of the second-order Stokes solution.

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The objectives of this study are to develop a layered biofilm model which expresses distributions of active biomass, dormant biomass, and extracellular polymer in biofilm with attrition in a methanogenic fluidized bed reactor, to discuss availability of the model in comparison with experimental results, to evaluate possibility of the existence of “dormant” biomass in the biofilm, and to estimate distributions of the active biomass, dormant biomass, and extracellular polymer in biofilm by the model. Comparing specific activities of sloughed and remaining biomasses with those of attached biomass, the existence of “dormant” biomass in the biofilm was indicated. The model is available to express distributions of specific activities of active and dormant biomasses in the biofilm with high accuracy.

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Texture measures of river revetments made from concrete blocks and stones, and of natural riverbanks are calculated. The natural feature of the revetment surface is quantified by Principal Component Analysis using the texture measures as variables. It is seen that stone pitching work bears good similarity as the natural feature which is given by natural riverside stones.

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The effect of adding water absorbing polymer (WAP) on formation of anaerobic granular sludge was evaluated in lab-scale UASB reactors using glucose or volatile fatty acid (VFA) mixture. The development of granular sludge was significantly enhanced by adding WAP. Granules developed on glucose and VFAs had high methanogemc activities and good settleability. The recommended dosage of WAP was between 750 and 1500mg/l of reactor volume. SEM observations suggested that rod-type Methanothrix-like organisms were prevalent species in the granules developed on the glucose while filamentous Methanothrix-like bacteria were predominant in the granules grown on the VFA mixture.

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