ON THE SCHEME OF ROUGHNESS ARRANGEMENT IN THE STEEP STREAM-TYPE FISHWAY BASED ON THE SWIMMING BEHAVIOR OF Tribolodon hakonensis

Abstract

 The purpose of this study is twofold. One is to examine hydraulic characteristics and swimming behavior of fish in the stream-type fishway with longitudinal slope of 1/20 and 1/10. The other is to propose a roughness arrangement that makes fish easier to run up in a fishway of steep slope. The experiments were conducted. As the results, the flow velocity of the stream-type fishway with a gradient of 1/10 was approximately twice as fast as that with a gradient of 1/20, and the run-up ratio of the Tribolodon hakonensis was low at 3.3%. Based on the results, the authors suggested the roughness arrangement combining aligned and zigzag, which was expected to improve the run-up ratio even if the flow velocity is fast. However, the run-up ratio was not improved. Accordingly, the authors proposed to set the roughness as a group, expecting that the roughness groups block the water flow, and the flow velocity around there decrease, which forms a resting place for fish. As a result, the run-up ratio was improved to 26.7%, which is eight times that of the previous case.