Abstract
Experimental tests and theoretical studies were made to investigate properties of small-scale bed topography that are step and pool systems widely observed in mountain streams. The findings are 1) the grain size distributions of the bed surface materials sampled in the typical mountain streams show the type of Talbot distribution, which is known to give the closed packing for heterogeneous materials; 2) the Talbot type grain size distributions of bed surface materials with an exponent n=1/2 to 3/4 is essential to the formation of the bed topography; 3) formulas for estimating a wave length and a wave height of the bed topography were proposed; in addition, 4) flow on the bed topography were classified into four types from experiments and with application of the Bernoulli equation. Based on the results, a design method of a new fish-way, of which shape and structure can be substituted spacing and height of a natural small-scale bed topography, was proposed. The fish-way proposed here have strong points that it can not only provide a habitat for fishes but also can draw off sediment in the pools by the own running flow.
