Author(s): Hiroshi Miwa; Himeka Nanba; Takashi Wada; Yuki Kajikawa; Shitetsu Matsuo; Yuuki Nakao
Linked Author(s): Hiroshi Miwa
Keywords: Multiple fixed weirs; Weir removal; Erosion and deposition; Flume experiment; Numerical simulation
Abstract: Because fixed weirs often negatively impact sediment management, their removal has been promoted worldwide. Therefore, it is important to understand the response of the riverbed to the removal of weirs. In particular, riverbed evolution in the case of multiple weirs may not only be influenced by the distance between them but also by the removal method adopted, that is, simultaneous or individual removal. These different scenarios have not been investigated sufficiently, and many factors therefore remain unknown. In this study, we investigated the effects of removing two weirs on riverbed evolution using flume experiments and numerical simulations. The difference in riverbed evolution between the simultaneous and individual removal of weirs was also investigated. The results are summarized as follows: (1) The upper and lower reaches of the weir trace gradually degraded and aggraded, respectively. These phenomena occurred rapidly during the initial stages of the experiment. (2) The riverbed aggradation area downstream of the lower weir trace due to the simultaneous removal of weirs was longer than that due to individual removal. Conversely, the riverbed degradation area upstream of the upper weir trace showed the opposite trend. (3) The numerical results reproduced the features of the experimental results. These results and methods may give a useful information to a planning of removal of weirs.
Year: 2024