Client: Melbourne Water
Product: StrataWebTM 445 – 100
Flood retarding basins are water impoundments designed to temporarily store stormwater runoffs to mitigate floods up to a 1 in 100 Annual Exceedance Probability (AEP) flood event while protecting natural waterways. When these basins store water they become reservoirs, potentially storing significant volumes of water, and therefore they impose dam safety risks on communities downstream. As a result, embankment hardening is often required to ensure the continued integrity and stability of the retarding basin due to erosion in case of a water over-topping event.
The project sites were various retarding basins, located in south eastern suburbs of Melbourne, where were recently assessed for risks by the Australian National Committee on Large Dams (ANCOLD).
Geosynthetic cellular confinement systems made of High Density Polyethylene were used modify the embankments in a cost-effective way to allow safe overtopping and ensuring embankment stability.
StrataWebTM Geocell was used to control erosion damage due to high velocities of the overtopped flood water on the crest and the downstream side of the embankment. A stable StrataWebTM installation foundation was created at the start of the construction by stripping all topsoil and organics from the surface, and the foundation was shaped to achieve levels as per design requirements. The geocell was then anchored at the crest and along the width of the embankment to provide shear and pull out restraint. This ensured that the shear stress exerted by the flow does not exceed the critical shear stress of the embankment material, thereby restricting erosion.