The Influence of Single Zigzag Type Porous Groin in the Change of Beach Profile

Abstract

Beach erosions have been faced as coastal problem and efforts to address the solution have been sought by the coastal researchers. One of the coastal protection structures that are commonly used are the system of groins. Various types of groins have been investigated and observed either in the Laboratory or directly in the field namely type of the forming material, length of the groins, the distance between the groins, and the width of the groin. However, groins with a zigzag shape are rarely investigated and studied. Hence, this paper reports on changes in beach profile due to the construction of single zigzag type of porous groins named GROPOZAG. The small scale of 1:20 physical model tests have been carried out at the Laboratory of River and Coastal Engineering in Engineering Faculty of Syiah Kuala University. Regular wave were generated in wave basin with 15 m long, 5 m wide, and 0.6 m deep. The influence of single groin length (Lg), and groins orientation perpendicular to the shoreline (θ) of 45°, 63°, and 90° under various wave steepness (H/L) of 0.0409, 0.0235 and 0.0200 with the beach profile of 1:20 slope are elaborated in this paper. Erosion or sedimentation is expressed in terms of sediment total volumes. It is found that groin with 90° orientation is more erosive than that of 45°. Straight porous groins erode more sediments than that of zigzag type porous groins. Zigzag porous groin is better in reducing erosion at the front head of the groin.