At EnviroStraw, we’re always innovating to help land managers, engineers and environmental professionals combat erosion – especially in areas where soils are highly dispersive and water flow is unpredictable.
One of the most powerful tools in our erosion control range is GeoSpray: a premium-grade surface stabiliser specifically engineered to protect bare earth from the damaging effects of concentrated water flow. But don’t just take our word for it. We recently commissioned respected soil scientists Landloch Pty Ltd to put GeoSpray through rigorous, independent testing. The goal? To assess its ability to prevent erosion in challenging soil types under channel flow conditions. The results were compelling— confirming that GeoSpray offers significant soil stabilisation benefits, even under extreme hydraulic stress.
The problem – fragile soils and fast-flowing water
Bare, exposed soil is one of the greatest risk factors for erosion. When left unprotected, even short-duration water flow – such as storm runoff or overland flow in newly constructed drains – can cause serious damage. The removal of topsoil, sedimentation of waterways and costly remediation work are all common consequences.
To test GeoSpray’s performance, the team at Landloch recreated real-world channel flow conditions in a specialised soil flume. The test soil was deliberately chosen to be dispersive, moderately sodic and light clay in texture – typical of the subsoils exposed during drainage construction in Australian landscapes. These soils are notorious for poor cohesion and rapid erosion under flow.
The test – bare soil vs GeoSpray
Two treatments were tested under increasing flow rates and gradients:
- Control: untreated soil (baseline)
- GeoSpray: applied at a rate of 4 kg/m² (dry matter equivalent), mixed with 900 mL of water per kg of product
Flow rates were increased in increments, with water depths and erosion effects monitored and recorded over several days. The flume system was calibrated to simulate gradients of 3.7% and 9.1% and flow rates up to 21.5 L/s were applied—equating to shear stresses up to 32.7 Pascals.
The results – clear water, stable soil
The difference in performance between the control soil and GeoSpray-treated plots was dramatic.
- The control plots began to erode at shear stresses as low as 5.5 Pa, with severe erosion observed at just 15 Pa. Suspended sediment was visible in the flow from the earliest stages.
- By contrast, GeoSpray-treated plots showed no erosion even at the maximum flow velocity tested. The water remained clear with no visible sediment movement or incision into the soil surface.
- Critical shear stress for GeoSpray-treated surfaces exceeded 30 Pa, representing a >200% improvement over untreated soil.
- Maximum permissible flow velocities were estimated between 2.6–3.2 m/s—comparable to values recommended for erosion control blankets, turf-reinforced mats and rock armouring.
Why it works – strength from the surface
GeoSpray acts like a protective skin over the soil. Once applied it increases cohesion at the surface layer, effectively holding soil particles in place – even under aggressive water flow. By reducing the detachment of particles and resisting incision, it provides both surface stability and clear runoff, which is critical for water quality management.
The report also noted that while slight “bulging” of the surface was observed at peak flow rates (due to pooling beneath the product), no failure or detachment occurred. This speaks to the resilience and durability of GeoSpray under challenging conditions.
Real-world applications
The findings from this study reinforce GeoSpray’s value in practical field conditions. It’s particularly suited for:
- Drainage channels and swales
- Roadside batter stabilisation
- Construction site runoff management
- Any exposed dispersive or sodic soils
Because it creates an immediate surface seal, GeoSpray is ideal for use in areas where vegetation establishment is slow or unreliable.
A smarter solution for soil stability
The science is in – GeoSpray not only works, it excels. Whether you’re engineering erosion solutions for infrastructure projects or rehabilitating disturbed landscapes, GeoSpray offers a reliable, tested method to protect soil and preserve the environment.