Abstract
In the Nakatsu river, after the dam construction in 2001, due to decrease of flood discharge, river course has been fixed, and gravel bar has been covered with vegetation. This study clarified the relationships between roughness of revetment and characteristics of morphological structures from dry riverbed to riffle-pool structures. At first, historical change of Nakatsu river is investigated. River width in the normal flow condition is stable for flow direction due to the concentration of flow, and the mechanism has been clarified through flume experiment. Secondary, through field measurement, in case the roughness of revetment is high, the stream line tend to be steep angle against the flow direction, and the morphology is different due to the difference of revetment roughness. Finally, flume experiment clarified the mechanism of how these difference appears under the controlled discharge
