Author(s): Tomohiko Fujita; Yasuyuki Shimizu; Yasumitsu Katou

Linked Author(s): Tomohiko Fujita, Yasuyuki Shimizu

Keywords: Fishway iRIC UTT simulation software

Abstract: Fishways are structures that are often discussed in the context of river environment conservation. In general, the function of fishways has been evaluated by monitoring their physical characteristics to determine whether they are suitable for upstream migration of fishes. However, because these surveys require considerable effort, post-evaluation and verification have rarely been conducted in detail in various seasons and for various fish species. Another major limitation is that the physical evaluation of fishways is often conducted only in a cross-sectional view. For example, evaluation is based on information such as the height of certain bulkheads, overflow velocities, and the depth of water in the pool. In general, a fishway is a series of units of a single form; hence, the entire fishway may be evaluated by extracting the structure of one representative unit. Therefore, it is possible that even if there are weaknesses in the fishway, they are often not specifically identified. Moreover, although there are many case reports on the upstream ability of fishes, such as their rushing speed, these may also be fragmentary data. Therefore, it can be said that there is no clear evaluation and visualization of the time taken and route adopted by fish that actually move up the fishway. Therefore, the simulation of fishway upstream migration was studied using the International River Interface Cooperative (iRIC) software. The iRIC was initiated by Hokkaido University and the United States Geological Survey. The iRIC software is a platform for numerical simulations related to hydraulic engineering. The software was developed as a river flow and bed fluctuation analysis software and has since been expanded to support various numerical simulation models such as inundation, runoff, tsunami, and debris flow models. One of the functions, the Universal Tracer Tracker (UTT), is a tool for tracking and visualizing the trajectory of various substances specified by the user in addition to the calculation results of various flow calculation solvers implemented in iRIC. In addition to the case where the target transported material moves entirely with the flow, it is also possible to express material movement by specifying its ability and characteristics when the material itself has a cruising ability; as seen in a typical example of fish. In this study, we used the UTT function to reproduce an actual fishway and attempted to simulate the fish run occurrence. The physical conditions of the fishway reflected those of the actual fishway, and the data on the fish run (cruising speed, cruising time, rushing speed, rushing time, upward method, and variation in body size) were extracted from published articles and used as parameters. In this presentation, we report on the actual simulation results under the above conditions and discuss the possibility of future utilization.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221296

Year: 2022