CHANNEL MORPHOLOGY OF MOUNTAIN STREAMS AND INHABITATION OF MASU SALMON

摘要

Morphological channel forms observed in many mountain streams show superposition of small-, medium- and large-scale bedforms. The small-scale bedforms are identified as step pool bedform of which origin should be antidune formation and sorting of bed materials. Medium-scale bedforms is corresponding to alternating bars composed of boulders and cobbles. Both bedforms coexist and are superposed. Prediction equations for the wavelength and height of a step pool can be derived from the theory of antidune. The first trial to construct a new type fish-way using the theoretical spacing for step pools was conducted in the site of Takizawa Dam. Field survey on inhabitation of masu salmon (cherry salmon) in a step pool stream was performed and it was found that the step pool system which provides both areas with high and low Froude numbers is a suitable habitat for salmon fishes.