Language：Japanese   Publisher：Japan Society of Civil Engineers  

The braided stream of the Abe River is considered to be formed by the non-equilibrium motion of the bed load and suspended load, which change significantly in time and space due to the complex riverbed topography of the braided channels. This paper presents the bed variation mechanism of braided bars in the Abe River by calculating the three-dimensional flows and non-equilibrium motion of the bed load and suspended load based on the time series data of the observed water surface profiles of the large flood in 2014. The calculation results could well explain the changes in mainstream positions due to the movement of the braided bars.

DOI： 10.2208/jscejhe.77.2_i_757

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> This paper aims at development of a non-hydrostatic quasi-three dimensional model for the flow in undular and hydraulic stilling basins. It is challenging for the depth-integrated model to calculate the flow separation at boundary surfaces (water surface and bed surface). To solve this problem, a non-hydrostatic quasi-three dimensional model considering flow equations on boundary surfaces (Q3D-FEBS) was derived. Q3D-FEBS was applied to the undular and hydraulic jump experiments. The calculation results are in good agreement with the observation data such as water surface profiles and velocity distributions of the undular and hydraulic jump. Moreover, it was showed that Q3D-FEBS can calculate the breaking process of the undular jump and formation of the surface roller. Finally, the applicability of Q3D-FEBS for the flow in hydraulic jump stilling basins was discussed against observation data of a large scale hydraulic model experiment.</p>

DOI： 10.2208/jscejhe.75.61

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Language：Japanese   Publisher：土木学会  

The middle Arakawa River has large flood plains, about 2.5km in maximum width. Flood storage functions of the middle Arakawa River had been strengthened by installing cross-levees which extend at right angles to levees and the Arakawa 1st retarding basin on the flood plains. New three retarding basins have been planed in the middle Arakawa River. This paper investigate the storage functions of the middle Arakawa River against the design flood hydrographs by numerical flood simulations based on the accurate flood flow model. The cross-levees increase the flood plain storage and delay the peak occurrence time of rate of storage. However, the large flood plains are filled with flood water at early stage of rising limb of the flood flows and do not have the sufficient storage space at the flood peak of the design hydrographs. For this reason, the peak discharge of the Iwabuchi control point exceeds the design discharge (6300m³/s).

DOI： 10.2208/jscejhe.74.i_1387

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

&amp;nbsp;Considering the dynamic boundary condisition at free surface (zero tangential stress) was the fundamental problem for applying the General Bottom Velocity Computation (GBVC) method to the flow over hydraulic structures with large water surface deformations. The zero tangential stress condition causes generation and flux of vorticity at the free surface. We formulated these processes and developed GBVC-FSV method. GBVC-FSV method was applied to the flow over a vertical sill. A comparison with the results of GBVC method indicates that GBVC-FSV can calculate the flows with large water surface deformations more stably.

DOI： 10.2208/jscejhe.73.I_667

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Language：Japanese   Publisher：土木学会  

DOI： 10.2208/jscejhe.73.I_667

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

The Go River confluences are composed of three rivers having a comparable drainage area. The prediction model for flood flows and bed variations in the confluences is needed for investigating the flow and bed variation characteristics and estimating flood water storages by the river confluences. This paper validates the prediction model based on the BVC method against water levels observed at 200- 400m intervals in the confluence during two large floods of different rainfall patterns. Moreover, the cause of the excessive bed scouring around the flow attacking point of the confluence is explored from observations about local bed profiles and conditions around the flow attacking point by using a radio control boat and unmanned submarine. The changes in local bed conditions around complicated flow areas are considered in order to refine the prediction model for flood flows and bed variations.

DOI： 10.11532/river.22.0_145

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

The Arakawa river has a plan to build new three retarding basins in the middle reach. It is important to understand flood control functions in middle stream of the Arakawa river with wide and vegetated flood channels. It is necessary to understand flood inundation mechanism on wide flood channels by flood flow analysis. Laser profilers can make use of the creation of detailed topographic maps of such flood channels, but may count the top height of vegetation on the ground. In this paper, filtering techniques of the laser profiler data are developed for reproducing proper ground heights of flood channels in the Arakawa river. Finally, the new flood analysis which improved the existing flood analysis method is presented.

DOI： 10.11532/river.22.0_133

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Understanding of the propagation mechanisms of the discharge and water level hydrographs in river channels is important for proper river management. It has been known that discharge hydrographs of flood flows passing through channel contractions are distorted by longitudinal difference of the storage volume of water in the channel. In this case, propagation mechanisms of the discharge and water level hydrographs are different, unlike in the case of the flood flow through a uniform channel. This paper characterize a part of the storage volume of water that causes the distortion of a discharge hydrograph as retarding storage volume of water and its evaluation method is proposed. We apply this method to a large flood through the valley of the Kitakami River and propagation mechanisms of the discharge and water level hydrographs are explained with relation to the storage volume and retarding storage volume of flood water.

DOI： 10.2208/jscejhe.70.I_721

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Understanding of the propagation mechanisms of the discharge and water level hydrographs in river channels is important for proper river management. It has been known that discharge hydrographs of flood flows passing through channel contractions are distorted by longitudinal difference of the storage volume of water in the channel. In this case, propagation mechanisms of the discharge and water level hydrographs are different, unlike in the case of the flood flow through a uniform channel. This paper characterize a part of the storage volume of water that causes the distortion of a discharge hydrograph as retarding storage volume of water and its evaluation method is proposed. We apply this method to a large flood through the valley of the Kitakami River and propagation mechanisms of the discharge and water level hydrographs are explained with relation to the storage volume and retarding storage volume of flood water.

DOI： 10.2208/jscejhe.70.i_721

DOI： 10.2208/prohe1975.27.721

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Language：Japanese   Publisher：土木学会  

In this study, the quasi-3D model composed of depth-integral vortex equation and shallow water equations was extended on the basis of finite volume method employing non-orthogonal grids for properly evaluating complex boundary of the confluences. And, we developed the flux integral method considering non-orthogonal direction of grid line based on the CIP-CSL scheme for evaluating the convection terms more accurately also in the complex flow field of the confluence. The extended quasi-3D model was applied to recent large floods at the Go River confluences to investigate the flood flow and bed variation during the flood events. From the calculation results, we clarified that separation zones formed at the confluences have pronounced effects on the three dimensional flow structure and bed variations for the downstream channel.

DOI： 10.2208/jscejhe.69.I_805

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

In this study, the quasi-3D model composed of depth-integral vortex equation and shallow water equations was extended on the basis of finite volume method employing non-orthogonal grids for properly evaluating complex boundary of the confluences. And, we developed the flux integral method considering non-orthogonal direction of grid line based on the CIP-CSL scheme for evaluating the convection terms more accurately also in the complex flow field of the confluence. The extended quasi-3D model was applied to recent large floods at the Go River confluences to investigate the flood flow and bed variation during the flood events. From the calculation results, we clarified that separation zones formed at the confluences have pronounced effects on the three dimensional flow structure and bed variations for the downstream channel.

DOI： 10.2208/jscejhe.69.I_805

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Language：Japanese  

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Publisher：Japan Society of Civil Engineers  

&amp;nbsp;In this paper, first, we discuss the physical interpretation of prop agation and transformation of water level hydrographs and discharge hydrographs by one dimensional equations for flood flows. And, relationships between storage volume of flood flows and propagation and transformation of discharge hydrographs are discussed for rivers with longitudinal changes in cross sections. From above discussions, we define &quot;retarding storage volume of flood&quot; which is the storage volume of flood when average velocities are decreasing during rising period of water levels.&lt;br&gt;&amp;nbsp;By using unsteady two dimensional flow analysis, we estimate water level hydrographs and discharge hydrographs of large floods through the valleys of the Kitakami River and the Go River. From this analysis, propagation and transformation characteristics of water level hydrographs and discharge hydrographs are explained with relation to river morphology, storage volume and retarding storage volume of flood in the river valleys. Finally, we discuss the application of this study for river plan ning and river management.

DOI： 10.2208/jscejhe.68.35

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Language：Japanese  

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Language：Japanese   Publisher：水文・水資源学会  

DOI： 10.3178/jjshwr.23.129

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

A series of small hydropower dams have been constructed along gorge sections of river in Japan. It is important to study hydraulic characteristics of flood flow associated with hydropower dams which will be usable for the future flood control management. At first, we show the effect of the gate operation of small hydropower dam on flood propagation speed and discharge hydrographs from observed results and unsteady 1D flow analysis which was developed so as to consider the effect of the gate operation. Secondary, storage functions of a gorge with a series of small hydropower dams are evaluated on the basis of the results of unsteady 1D flow analysis before and after the construction of a series of small hydropower dams.

DOI： 10.3178/jjshwr.23.129

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

There are a lot of river with long gorge sections in Japan. Because considering the balance of upstream and downstream reaches is the base of the flood control management, river improvement in gorge sections is a fundamental issue. So, it is important to understand the flood propagation mechanism in gorge sections. But because of the lack of the observed data in gorge sections, enough studies have not been conducted.

In this study, we show the mechanism of flood propagation and the effect of the channel form on flood propagation in the gorge section of the Go River and Kitakami River from observed data and using the unsteady 2-D flow analysis.

DOI： 10.11532/river.16.0_425

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