Variation of the Side-Weir Discharge Coefficient Associated with Submerged Ratio

The studies on the subject have been generally focused on free overflow of side weirs located on a straight channel. On the other hand, the studies for the submerged flow over the side weir have not been conducted sufficiently. In the case of insufficient detention basin capacity, both free and submerged overflow occur at a side-weir. Therefore, for the accurate estimation of flood-control effect of a side-weir detention basin, it is strongly suggested to investigate the side-weir discharge coefficient for submerged-overflow case. In this study, the discharge coefficients of side weir have been estimated through experiments with various depths of river(H) and detention basin(D). The results show that the submerged-discharge coefficients decrease with D/H when D/H is larger than 0.75, while the submerged-discharge coefficients coincide with those for free overflow cases when D/H is less than 0.75. A new relation between reduction factor (discharge coefficient for submerged flow /discharge coefficient for free overflow) and D/H is proposed and compared with plain weir's in this study.