Influence of the Relative Separation on Sediment Transport Processes Around Arrays of T-head Gabion Groynes

In this contribution, the authors studied the influence of the relative separation length (S_p^*= S_p/L_to, where S_p is the separation between groynes and L_to is the groyne length) on sediment transport processes around gabion groyne arrays. Experimental data coming from a previous study, consisting in scour depths produced by several installed arrays of four T-head groynes in a rectangular tilting flume, under submerged conditions, uniform sandy bed and discharge, were used for calibration and validation purposes. Eight empirical formulas from the scientific literature were used to assess their accuracy for the estimation of scouring depths. Most of these models underestimated or overestimated the observed values in the laboratory. Hence, dimensionless analysis was carried out to propose four new empirical models. 70% of the experimental data was used for the calibration of these new formulas, whereas the remaining 30% was employed for the validation phase. Two out of the new four models estimated the scouring depths properly, demonstrating the direct influence of the relative separation length in between structures on scour depths in their near vicinity. Nonetheless, it is necessary to carry out more experimental research in order to further asses and confirm the accuracy of the new formulas.