Bank erosion is one of the critical challenges in river engineering, an‎d spur dikes are considered as an effective structural measure to mitigate this problem. These structures function by reducing the local flow velocity an‎d diverting the stream toward the river centerline, thereby protecting the erodible banks. While numerous studies have investigated the performance of single an‎d series spur dikes, limited attention has been given to the determination of optimal spacing an‎d the hydraulic characteristics of permeable spur dikes, particularly those constructed from gabions. The present research aims to eva‎luate the optimal spacing of impermeable an‎d gabion spur dikes. Gabion spur dikes, owing to their lower construction cost an‎d ease of implementation, offer significant advantages over other types of permeable structures. Experimental tests were carried out using three impermeable spur dikes with widths of 20, 30, an‎d 50 cm, as well as one permeable gabion spur dike with a width of 30 cm. The experiments were conducted under Froude numbers ranging from 0.11 to 0.40, three discharges (20, 44, an‎d 54 L/s), an‎d four different submergence conditions. The results indicated that increasing spur dike width leads to a larger recirculation zone an‎d that permeable spur dikes perform more efficiently compared to impermeable ones. Moreover, the optimum spacing between spur dikes was achieved when the subsequent structure was located at the end of the preceding recirculation zone. To validate an‎d complement the analysis, flow velocity measurements were obtained using an Acoustic Doppler Velocimeter (ADV). The processed data, visualized through Surfer software, were used to generate spatial velocity distributions an‎d identify recirculation zones. Numerical analysis with Surfer showed satisfactory agreement with the visual dye-tracing experiments, confirming the reliability of the laboratory observations. Ultimately, based on dye injection tests, the appropriate spacing between spur dikes was determined, an‎d an empirical relationship was proposed to estimate the optimal distance

منوچهر حيدرپوراسفرجاني

سعيد صالحي هفشجاني

مهرنوش جعفري , الهام فاضل