11/06/2026
What's actually causing the ground to sink behind your canal wall?
The photo is the inside of a weephole on a Bribie Island wall. See all that sand sitting in the bottom?
That sand came from behind the wall.
It shouldn't be there. Subsidence is one of the most common problems we find on aging canal walls, and most homeowners don't realise it's happening until they notice a crack in their path or a dip in the ground near the waterfront edge. There are three main ways it starts.
1. Weepholes losing material. Weepholes are the small holes in your wall that let water drain through. They're meant to have a filter fabric behind them to hold the sand in place. When that fabric breaks down, sand moves through with every tide. Slowly, the ground behind your wall hollows out.
2.Unsealed or failing joints. The vertical joints between your wall panels are sealed with a rubber compound. Over time that sealant deteriorates, especially below the waterline. Once it fails, each tidal movement pulls a little more material out through the gap.
3.Water pushing under the footing. If water finds a way beneath the base of your wall, it carries material with it as it moves. This one tends to be the most serious because by the time it's visible, the damage underneath is usually already significant.
The good news is that all three causes are detectable early during a proper inspection, and they're all fixable before they become expensive.
If your wall hasn't been inspected recently, it's worth getting it checked. Head to www.canalwalldoctor.com.au to find out more or book an inspection.
The Canal Wall Doctor is a team who inspect, report and repair revetment walls in canals and rivers in Bribie Island, Raby Bay, Redland Bay, Gold Coast
