Investigation for the design of new fish way to be modeled on step and pool systems in mountain streams

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This study aims to establish the way of design of a new fish way as is modeled on a natural mountain stream with step and pool systems on the bed, which is assumed to be constructed as a by-pass adjacent sediment reservoir dam etc. From investigation into the bed topography and the function to the creatures in natural mountain streams, following facts and way of design were found.1. A steep channel consisting of the pebbles with Talbot grain size distribution. in weight is suitable to construct a fish way, since there will develop alternating bars as Knell as step and pools on the bed to provide well habitat far aqua creatures.2. Three kind of structures can be seen in the step systems in mountain rivers such (1) consisting of the uniform pebbles aligned transversely to the channel, (2) consisting of the small pebbles those sequential form shows complex connecting circles with different diameter and (3) consisting of the big pebbles and boulders those sequential farm shows simple conne … More cting circles. For the fish way, the structure of (1) can be easily constructed, however, the pool to be generated will be shallow The structure (3) can provide a diversity of habitat with deep pools, however, this type of structure develops only at a reflection point of flow (top of a bar front) in natural rivers.3. Individual numbers and density of benthos living at the step of (3) are greater or higher than those at the step (1). Then, individual numbers of benthos at a part of step are greater than those at the part of downstream pool, but the tendency becomes reverse on the number of species, because organic nutritive matter line dead leaves can be trapped at the chinks between step stones and rapid flow on the step selects the species possibly to stay on the surface of step stones.4. According to results of examination for contents of the stomach, fishes of salmon family have a nature to take terrestrial insects (94%), and domiciliation fishes eat mainly aqua insects (99%).5. Design of a fish way will be conducted as : to determine the space length and height of steps with the data of bed slope, design discharge and grain size distribution of bed material, to decide the channel width by considering the generating condition to alternating bars, to prepare the artificial step structure consisting of the pebbles and boulders in place, to arrange the steps with the form of (1) or (3) and to lay the soil in place, to run water for self forming the pools, and to plant vegetation for covering the channel. Less