Abstract
Boulders are sometimes placed in rivers to enhance an ecological function by making diverse bed configuration. However, large-scale roughness causes water level rising in flood events. It is necessary for flood control measures to evaluate resistance characteristics of rivers with large boulders. In this study, water level was measured in an open channel with various patterns of cube groups. The resistance to flow of each case was evaluated as a water level rising ratio and Manning's roughness coefficient calculated from 1D numerical calculation. Then, 2D depth-averaged equations were applied to estimate the water surface profiles in these experiments. For improving prediction accuracy it is proposed to set the wake flow region behind roughness and the impinging area in front of roughness as the dead water zone.
