Following the 2018 flooding at the Northbrook ponds the council necessitated a design review for a one in 50 year flood event of the railway drain overflow.
Geofabrics provided design guidance and anchorage calculations based on a horizontal anchor resistance of 50 KN/m2. The design consisted of an increased height of the northern bank of the railway drain near the inlet to Northbrook settling pond and a widening of the railway drain that runs east of the settling pond inlet.
The widening created steep banks two to four metres high at a slope of 1:1. To stabilize the exposed soil on the slopes, Geoweb geocell cellular confinement system was installed with Bidim A29 geotextile underneath the toe of the slope.
The Geoweb was anchored using steel rods at a rate of 1/m² and the Geoweb cells filled with a soil mixture then covered with coir matting. In total there was 1,230 m² of Geoweb GW30V 100 mm.
To complete the installation, native shrubs and grasses were planted in the slopes to aid slope stability and to replace what vegetation was removed for the upgrade.
Both the contractor and council were happy with the result.