Abstract
Recent river channel improvement projects in Japan are almost occupied by richin-nature river works. River engineers are compelled to be conscious to nature in and of rivers. However, philosophy of nature concerning to river has not been discussed before the rich-in-nature improvement project and fundamental functions of such works have not been studied as well. In this study, rich-in-nature types of revetment were discussed and hydraulic model tests were carried out to investigate flow characteristics and hydraulic functions of a step type of revetments. Secondary currents as observed in channels with compound cross sections appeared in each step. Toe protection with boulders showed a great effect of velocity reduction.
