The Effectiveness of Permeable Pile Groyne as Riverbank Protection: Case Study on the Konaweha River, Southeast Sulawesi

The erosion at the Konaweha River bend (434310.10 E, 9559834.07 S) has occurred massively and rapidly. Changes in land use downstream have worsened the morphology of the river. Since 2014, erosion has steadily progressed and by 2019, it had destroyed structures on the riverbank, including homes and the national road. This study proposes to examine the effectiveness of permeable pile-type groyne in managing flow at river bends and mitigating riverbank erosion. Initially, a hydrological analysis was conducted to acquire a discharge in the 50 year return period, i.e., 3638 m³/sec, followed by a groyne design to determine the shape, dimensions, and positioning (7 series of goryne was proposed). Subsequently, mathematical modeling using the IRIC-Nays2D was used to study flow patterns under existing conditions and after the installation of groyne structures. The domain width and length for the simulation were set at 100 m and 494.828 m, respectively. A rigid (fixed) bed condition was assumed with a focus on the hydrodynamic response and induced flow patterns. Based on the simulation results, erosion at river bends occurs due to the presence of secondary flows in the form of vortices with velocities of up to 2.80 m/s at the bank. The installation of groyne could reduce this by 74%.