Assessment of Best Configuration of Cocolog Groynes in Meanders Considering Scouring and Flow Patterns - An Experimental Study

Cocolog groynes are new form of soft stabilization method, which can be used for restoration of river meanders. After an extensive literature review, it was observed that conventional impermeable groynes behave in a different manner compared to the cocolog groynes which are permeable in nature. Hence, the objective of the present study was to analyze the effect of significant geometrical and hydraulic properties of cocolog groynes on scour and flow patterns in meandering channels. The experimental studies were conducted in a scaled physical model of meandering channel with series of cocolog groynes installed at aspect ratios between 2 and 4, density ratios between 0.12 and 0.18, relative lengths between 0.14 and 0.2 and for orientation angles from 30o to 150o. The desirable range of these parameters for cocolog groynes in meandering channels were obtained as 2.5 to 3.0, 0.14 to 0.16, 0.16 to 0.18 and < 90o, respectively, after analyzing the bed scour and dimensionless mean velocity in both streamwise and transverse directions. The study provides an appropriate layout of an eco-friendly soft river bank stabilization technique, which not only promotes vegetation but also restores the river banks.