Determination of Discharge Coefficient in Gabion Weirs at Free and Submerged Condition

Weirs are hydraulic structures that are built for regulating, controlling and diverting water in the flow direction. Gabion structures are used extensively in water projects due to the ease of construction, permeability, accessibility and economic efficiency. Porous gabion structures are adaptable to the environment due to their material and performance and also are valuable from ecologic view point. In this study, 8 physical models of gabion weirs and 2 models of solid weirs were built for determining discharge coefficient in gabion rectangular broad crested weirs. Comparisons between gabion weirs with solid weirs were done and they showed that the discharge coefficient in gabion weirs was greater than that in solid weirs. In addition, the regression relations based on the dimensional analysis for the flow through gabion weirs were obtained for both the free and submerged conditions. Results showed that the discharge coefficient of gabion weirs in free condition was 16.7 % greater than that of the submerged condition.