A Hydraulic Model Experiment on the Relationship Between Sediment Transport Characteristics and Changes in Watercourses around a Low-Water Revetment or Spur Dikes

Low-water revetments and spur dikes are effective in mitigating lateral erosion; however, they greatly change the flow regime and sediment transport characteristics around them. Clarifying the influence of these facilities on the watercourse characteristics is important for efficient river development and from the viewpoint of protecting the river environment. Much remains to be explored regarding the sediment transport characteristics around the revetments, including the relationship with changes in watercourses. On the contrary, there have been many studies on the flow and sediment transport characteristics around spur dikes through many onsite surveys, flume experiments, and numerical analyses. Many studies have been done on the effectiveness of spur dikes in directing flows away from the bank and on the scouring that occurs at the end of the spur dikes. However, these examinations were mainly on spur dikes themselves and they did not attempt to clarify the influence of the changes in the sediment transport characteristics or the changes in the watercourse to the downstream section of the spur dikes in fast flowing rivers. In this study, the responses of a watercourse, when bank erosion at a water colliding front was controlled by a low-water revetment or a spur dike, was investigated in a hydraulic experiment. The subject was a meandering channel with bank erosion, which is often seen in a fast flowing river during a flood. Not only the watercourse in the section, where the revetment was installed, but also the watercourse downstream of the revetment became straight, and the watercourse characteristics of the meandering channel were lost. Although bank erosion was able to be controlled by spur dikes in the same section as for the revetment, the spur dikes did not change the meandering watercourse characteristics immediately downstream of the section. This study shows the influence of the characteristics of sandbars, which develop downstream-ward along a revetment, on the watercourse characteristics downstream of the revetment. This study also discusses that changes in the watercourse at the downstream section of the spur dikes is greatly influenced not only by the sediment transport characteristics of the section around the spur dikes, but also by the sediment transported from the upstream sections.