Experimental investigation of gabion grade control structures on hyporheic exchanges

The hyporheic zone is a region immediately beneath the riverbed where surface and subsurface water mix, this research seeks to identify methods to increase the sedimentation rate in sedimentation basins. To this end, this study aims to (i) examine the effect of creating submerged walls on the efficiency of sediment trapping compared to a simple sediment basin, (ii) evaluate the influence of variation in wall height on sediment trapping efficiency, and (iii) study the effect of the number of walls on sediment trapping efficiency.The laboratory flow's length, width, and height were 5 m, 30 cm, and 0.5 m, respectively. The experiments were performed at Gorgan University of Agricultural Sciences and Natural Resources on a one-, two-, and three-step gabion spillway. Notably, three distinct basin lengths were used in the 3-step case test. Afterward, numerical modeling was employed to analyze the experimental findings.According to the results of the gabion spillway, as the number of steps increment, sedimentation rate, sequestration, and consequently flow retention time increase. Analysis of dimensionalized total flow rate (q*) in all three spillways revealed that this parameter decreases as the Reynolds number increases. In addition, the obtained power law for this parameter in terms of Reynolds number demonstrated correlations of 81, 88, and 98 for one-step, two-step, and three-step spillways, respectively.This study demonstrated that the presence of a hydraulic jump alongside a gabion stabilizer increased hyporheic interactions. As a result, increasing the flow rate increases the hyporheic interaction rate while decreasing the flow retention time.