Sydney’s geology varies sharply from the Hawkesbury Sandstone plateaus in the north to the Wianamatta Group shales in the west, creating highly heterogeneous infiltration rates across the metropolitan area. In the eastern suburbs, where sandy soils overlie clay layers, a single-ring or double-ring infiltrometer is essential to separate vertical from lateral flow. We perform these infiltration tests in accordance with AS 1726, measuring soil hydraulic conductivity at multiple depths to avoid overestimating soakage capacity. For projects requiring continuous permeability profiles, we combine this with permeability in laboratory testing on undisturbed samples, ensuring the field data correlates with lab-based saturated conductivity results.
A double-ring infiltrometer isolates vertical flow from lateral spreading, critical for accurate soakage design in layered Sydney soils.