Rainstorm flood, landslide and debris flow frequently occur in mountainous area, and then lots of coarse particles such as pebble, gravel, boulder with wide size distribution have been entered into open channel. Boulders obviously affect characteristics of flow structure and bedload transport around these boulders. On the basis of the field investigation of boulder riverbed and series of flume experiments with limited water depth, the influence of boulder on the riverbed deformation and bedload transport rate have been analyzed and discussed. The results show that the increase of flow turbulence becomes stronger behind the boulder with the decrease of boulder particle relative exposure degree (D/h, ratio between boulder equivalent diameter and mean water depth), the scour ability has been enlarged, and the more bed material were transported. According to the bed surface coarse degree and boulder dissimilar state, several of experimental cases have been carried out in order to understand the variations of bedload transport rate, changes present that the influence of boulder on bedload transport rate may be several times to ten times with the premise of the flow-sediment conditions in this study.
