Adelaide’s beaches are affected by a common phenomenon called longshore drift - the flow of water, in one direction, along a beach occurring as a result of winds and currents. In Adelaide longshore drift flows from south to north and it frequently erodes beaches over time, particularly during storm events when tides are high and sea is rough.
Without sand replenishment, the southern end of Adelaide’s beaches will slowly erode and undermine existing infrastructure at the sea/land interface. The objective of Elcorock sand container groynes, laid perpendicular to the beach, is to capture some of the natural sand as well as dredged sand, that moves along the coast. Over time, this process builds up the beach, particularly between the groynes which results in the protection of the existing infrastructure.
Geofabrics met with the City of Holdfast Bay in the early stages of the project to discuss the product, durability and previous projects with a similar application. Due to recent weather events, the beach erosion was extensive and public pressure extreme. The city was therefore keen to accelerate installation to reduce risk of further damage to existing an rock revetment and the adjacent road.
The Elcorock coastal erosion system was selected due to its aesthetic appeal (in comparison to rock groynes), and its relatively low cost installation cost. The fill material was also able to be sourced directly from the beach.
The two groynes were approximately 30 m long and spaced 50 m apart. Each groyne was made of 50, 2.5 m3 Elcorock sand containers.
Geofabrics provided guidance in both planning and installation stages, offering guidance on installation times and process. Geofabrics also assisted onsite during the initial two days of installation to ensure the bags were filled and installed correctly.
Two years later and the beach is looking great with significant build-up of sand occurring, having protected the rock wall and road. With no visual damage to the sand bags, the council is extremely happy with the result and has gained funding for two more groynes in the coming months.