To clarify the spatial distribution of throughfall characteristics under a canopy of Japanese cypress (Chamaecyparis obtusa), indoor experiments were conducted using an 11-m-tall transplanted tree and a large-scale rainfall simulator with spray nozzles at a height of 16 m. Throughfall was measured for 10 minutes using 120 rain gauges set in a lattice-like arrangement. Eleven experimental conditions for artificial applied rainfall and throughfall were created, using two different rainfall intensities, the first-branch heights of the tree, and measuring-point intervals. Compared to the applied rainfall, the throughfall had larger spatial variability; the ratio of the throughfall to the applied rainfall ranged from 40 to 484 %. Throughfall generally increased with distance from the stem, and particularly large throughfall was measured along the canopy edge when the applied rainfall consisted of drops with smaller kinetic energy. Changing the intensity of applied rainfall changed the spatial distribution of throughfall in each quadrant under the canopy. Dripping points, where much larger throughfall was measured than at other points, were observed near the stem. Large differences in throughfall were also found between measurements before and after pruning, at locations adjacent to the pruned branches. The results indicate that the spatially heterogeneous distribution of throughfall was organized by the distance from the stem and the branch arrangement in the lower canopy layer.

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Inflow into a dam reservoir is estimated from a time variation of the hydrostatic water level. Therefore, noise in the time series data of observed water level causes an oscillation of estimated inflow. The noise originates from water surface oscillation in the reservoir. Recently, some effective smoothing methods to eliminate the noise have been proposed. In the case of a multi-reservoir system, an estimated value of inflow requires a value which is eliminated the influence of the noise, and also correspondence to the outflow from the upstream dam. However, an exact quantity of the inflow was not discussed in the studies about smoothing method.
In this study, dam water levels at some reservoirs along the Jinzu River were measured. The inflow of each dam reservoir was calculated using an inflow estimation method based on a the digital filter. It was confirmed that an accuracy loss of the outflow sometimes occurred. In a small reservoir, estimation of inflow from the water level is not accurate in flood times, because the flood wave of the water level has time lags compared with that of discharge. And this study indicated that the inflow at the downstream dam was effective data for the evaluation of the inflow at the upstream dam in a multi-reservoir system connected in series.

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This study aims at evaluating the impact of climate change on flood disasters and dam reservoir operation in the Yodo River basin by feeding precipitation and evapotranspiration projection from Global Circulation Model (GCM) to a distributed hydrologic model. The features of the conducted hydrologic simulation are 1) dam reservoir models are integrated into a hydrologic model; 2) a distributed hydrologic model is used with lumping of rainfall-runoff processes for a sub-catchment scale covering about 10 km² ; and 3) stochastically downscaled hourly precipitation from daily precipitation are used to drive the hydrologic model. The simulation results indicated that the frequency of medium magnitude floods might increase in 2031 to 2050, while the intensities of low frequent severe floods might increase in 2081 to 2100. In addition, the frequency of emergency operation by the Hiyoshi Dam in the Katsura River basin was estimated to increase in 2031 to 2050.

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Quantitative understanding the characteristics of water deformation and height development is crucial for river management and river flood disaster prevention. Particularly in heavily meandering reaches the centrifugal forces could have a significant influence on increasing water height near the outer banks and the risk of disasters like levee breaks, overflows and floods could be larger. In this study we attempted to model the wave height development in a meandering river reach. Two dimensional wave equation and Euler equation were derived and a new wave equation was finally obtained based on an orthogonal curvilinear coordinate system to simulate the ascending wave in rivers with a complex meandering shape. This equation takes into account the centrifugal forces and river shape. The performance of the new equation was demonstrated using a single meandering river reach with a rectangular cross section. With a series of simulations with different meandering curvature values, we demonstrated that ascending wave length, radius of curvature and channel width had important roles in deformation of the ascending wave form and water level increase in a meandering part of the channel.

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