Study on recent change of gravel-bed river landscape and river forestation

砾石河道景观近期变化及河流绿化研究

基本信息

批准号：
16560443
负责人：
SHIMIZU Yoshihiko
金额：
$ 2.05万
依托单位：
Gunma University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16560443/
关键词：
gravel bed river forestation Robinia pseudo-acacia formation of low-water course driftwoods distinct element method depth areraged flow analysis 交互砂州移動限界礫径比高差の拡大河相変化

项目摘要

As recent channel characteristics of gravel-bed river, bed degradation, immobilization of the low-water course, local scour near river bank, extension of relative elevation, and overgrowth of vegetation are mentioned. Especially, the occurrence of riparian trees in the course of gravel-bed rivers has been very much increasing, which produces source of driftwoods in rivers. First in this study, recent characteristics of gravel-bed river and factors that cause the forestation of the river channel were investigated by analysis of the changes in both the channel cross-section and the woodland in the gravel segment of the River Watarase, a tributary of the River Tone. Here we focused on the excessive growth of Robinia pseudo-acacia, the representative species in river forestation.These channel characteristics in gravel-bed river are produced as results of the morphological change under the medium-size floods in the low-water course affected by alternate bars. We also discuss the low-water channel formation where recent river channel characteristics of the gravel-bed river are reflected, and the process of morphological change was examined from numerical calculation. First, a channel with alternate bar was made, afterwards, the flow discharge was lowered and the meandering low-water channel, which brings about the bank erosion and local scour, was formed. These processes were investigated from the results of present numerical calculation.Finally, a numerical simulation method has been developed for describing the behavior of driftwoods motion and their accumulation process. The present model has been composed of Eulerian analysis of fluid motion given by depth-averaged flow analysis and of Lagragian analysis of driftwoods motion by using the extended Distinct Element Method (DEM), which can simulate the motion of driftwood as the rigid body.

随着碎石河河流的最新渠道特征，床降解，低水道固定，河岸附近的当地气泡，相对高程的扩展以及植被过度的过度。尤其是，河岸树在碎石河过程中的发生量已经大大增加，这会在河流中产生浮木的来源。首先，通过分析河水河河河（River Watarase）的砾石段（河流的支流）的变化，研究了砾石床河的最新特征以及引起河道森林的因素以及导致河道森林的因素。在这里，我们专注于罗比尼亚伪阿卡西亚（Robinia pseudo-Acacia）的过度生长，河林中的代表性物种。这些河流河中的河道特征是由于在中等大小的洪水下的形态变化而产生的，在中等大小的洪水下，低水道受到替代条的影响。我们还讨论了低水通道的形成，其中反映了砾石床的近期河道特征，并从数值计算中检查了形态变化的过程。首先，随后建立了一个带有替代条的通道，然后降低了流量排放，并形成了蜿蜒的低水通道，该通道带来了河岸侵蚀和本地冲刷。从当前的数值计算的结果中研究了这些过程。从最后，已经开发了一种数值模拟方法来描述浮木运动的行为及其积累过程。本模型由通过使用扩展的不同元素方法（DEM）进行深度平均流量分析和浮木运动的拉格拉格分析的流体运动分析组成，该分析可以模拟浮木作为刚体的运动。