Case Study
Far North Queensland Island Drainage – Four Years Later
The Project
In 2022, drainage improvement works were undertaken along a main road on a coastal island off Far North Queensland. An existing drain was upgraded to increase capacity and improve flow, reducing flooding to the adjoining roads, residential areas and nearby parklands.
Global Synthetics was engaged to supply geosynthetic products for the project and recently had the opportunity to revisit the site four years later to see the installation performing as intended. Here's a look at what was used and how each product contributed to the successful design.
The Challenge
The site presented several considerations during the design phase. The foundation consisted of clay soils prone to movement and swelling when exposed to changes in moisture. This made it critical to provide adequate separation and reinforcement to prevent subgrade failure.
The drain also needed to withstand heavy flows during significant rain events, which are common in the Far North Queensland region, without erosion of the channel batters or loss of structural integrity over time.
The Solution
Following civil engineering works to shape the drain and provide a new channel deep enough to support flows during heavy rain events, a Geofirma geotextile was laid as a separation layer to secure the sand base and allow filtration.
Naue Combigrid (geocomposite subbase reinforcement) was also laid on the base of the drain to provide additional separation, filtration and reinforcement for future access if required. The high extensional stiffness of Combigrid reduces deformations in the subgrade which in turn extends the service life of built infrastructure on top.
Armormax® Vegetation System with PYRAMAT®75
The PROPEX Armormax® Vegetation System consisting of Pyramat 75 High Performance Turf Reinforcement Mat and B3 Percussion Anchors, was then installed on the batters at a depth of 3m to ensure locking and tension into the clay foundation. Engineered to provide long-term design life, the Armormax system locks soil in place to resist movement for permanent erosion protection.
The Result
Four years later, following further rain events since completion of the project, the drainage channel has held its integrity and has provided a reduction in flooding to the area. With a 75-year design life, the results are built to last long after the project is complete.
