Abstract
To elucidate influence of bedrock cover thickness on bar morphology in free bar generating condition, we conducted hydraulic experiments. We changed bed material thickness (less and enough for fully grown bar height) and bedload feed rate (equilibrium state and 30% of equilibrium state). The results showed that bedrock exposures around bar fronts were stretched in the case bedrock cover thickness is thinner than fully grown bar height. But, in the case bedrock cover thickness is same as fully grown bar height, the exposures were not stretched. We assumed that easiness of bedrock exposer by bed material erosion and exposure rate at bar formed time related to the occurrence of exposure stretch. In the combined condition case of enough bed material thickness for bar height growth and 30% of equilibrium bedload feed, the exposure rate was not increased during experiment.
