A Method for Restoring the River Environment by Restoring Meanders

2003年至2005年进行了研究，以开发重新连接志别川上切断的河曲的方法。以往的调查表明，在试验场的两个渠道恢复，曲流渠道重新连接，而拉直的渠道是保持有希望的防洪和环境恢复。在动床水力模型试验中，模拟中尺度沙波作用下的河床冲刷时，最适宜的床料是比重和粘度较低的床料;在现场调查的基础上，提出了一种基于河道修复后和河道拉直后的形态，研究两条河道在分汇流处最佳河道中线的方法。当河道分叉时，汇流处的河床退化不能被阻止。3）在急剧转向的河岸位置，樱花钩吻鲑在更高的人口密度和更多样化的年龄分解时，放置倒下的树木比没有倒下的树木时，被观察到。通过对牛轭湖（截弯河）污染物收支的调查和水质模型的建立，验证了模型的适用性。通过建立湿地地下水位的估算模型，阐明了河流水位变化对附近河流地下水位变化的影响。

Research was performed from 2003 to 2005 toward developing a method of reconnecting a cut-off meander on the Shibetsu River. Previous surveys at the test site showed that two-channel restoration in which the meander channel is reconnected while the straightened channel is maintained has promise with respect to flood control and environmental restoration. The findings are summarized here.1)In movable-bed hydraulic model tests to reproduce bank erosion at river channels where mid-scale sand waves occur, the most suitable bed materials were those low in specific gravity and viscosity.2)From field surveys, a method for studying the optimum channel centerline at the divergence and confluence of the two channels was developed based on the shapes of the restored channel and the straightened channel. When channel bifurcation is conducted, riverbed degradation at the confluence cannot be ignored.3)At riverbank locations of sharply redirected flow, cherry salmon were observed in higher population densities and more diverse age breakdowns when fallen trees were placed than when no fallen trees were placed. Such placing is expected to be effective in fostering a favorable habitat for fishes.4)By surveying the pollutant budget of the oxbow lake (the cut-off meander) and by constructing a model for estimating the water quality, the applicability of the model was confirmed. By developing a model for estimating the ground water level in wetlands, the effect of changes in river water level on changes in ground water level near the rivers were clarified.