2002 Volume 46 Pages 695-700
Transverse ribs are popular existences in a mountain river, those are composed of the transverse lines of large cobbles across a stream. For intension to apply the rib-step morphology to a fish-way, knowledge is desired on the configuration structures of rib-steps. Present paper describes results of field survey for the Gunbetsu River to clarify plan forms, rows of cobbles etc. of the ribs, and also deals with configuration features of experimentally formed ribs in a laboratory channel. From the both results, followings were found: Plan form of a transverse rib is not necessarily straight but curved line with S-shape or M-shape is more popular. The former transverse ribs are formed by comparatively large cobbles, while the latter transverse ribs are composed of the cobbles with various diameters. Correlation with respect to the diameters of adjacent cobbles is not strong, which shows the order of cobble diameters is rather random.
