Living Seawalls for Sydney Harbour

Name: Codi
Price range: $

Mosman

Natural shoreline is very important for marine biodiversity.

If you look at the beautiful Chowder Bay, on the Mosman Peninsula, for example, and you look at our intertidal areas, our intertidal areas are on a slope quite often.

Chowder Bay Phill Pullinger — The beautiful Chowder Bay in Sydney Harbour. Image: Phill Pullinger

Sydney Harbour is made up of Hawkesbury sandstone.

Sandstone weathers in very particular ways and very unique ways. In that intertidal area, you get things like rock pools, and shallows. When the tide goes up and down, this intertidal area is an area that is teeming with biodiversity. The intertidal area is in fact one of the more important ecological environments that we have in our shorelines.

Sandstone and Bridge Phill Pullinger — Sandstone and its unique weathering is an important part of the natural shoreline of Sydney Harbour. Image: Phill Pullinger

Foreshore view to Sydney Phill Pullinger — The intertidal area, with its rock pools, shallows and complex features, is an area that traditionally teeming with biodiversity. Image: Sydney Harbour foreshore, Phill Pullinger

In Sydney Harbour, certainly upriver, nearly 100% of the natural shoreline has been transformed to artificial shorelines.

Because natural shoreline is so important for marine biodiversity, what the Sydney Institute of Marine Sciences is doing with our living seawalls project, is we're trying to mimic a lot of natural structures that we see. So with the living seawall tiles, we have 10 unique designs. Some of them mirror what we'd see in mangrove groves, some of them mirror what we would see in small rock pools and pockets. We are able to install them onto vertically built structures, which increases the surface area, increases things like water retention when you have tidal changes, and what we see in a typical installation we have of a living seawall, we install about 72 panels, and it usually covers, that's usually sort of covering a depth of about two to two and a half metres of intertidal range.

Living Seawalls Sydney Harbour SIMS — An area of Living Seawall established by the Sydney Institute of Marine Science in Sydney Harbour. Image: SIMS Collection

If you look at the ecological diversity in an installed living seawall compared to seawall areas adjacent, we see about 300% improvement in biodiversity of typically naturally occurring species.

We've got a large installation around Barangaroo, we have seen some introduced species there, which is a problem, we don't want to encourage and populate introduced species into the harbour, which might have come off the holes of boats and things like that. But what the studies have shown, is if we can control that early on and let the natural species establish, then it completely blocks out the introduced species. You then get a multiplier effect of restoring local species at the expense of potentially invasive species.

Attaching Seawalls SIMS — Attaching Living Seawalls, Sydney Harbour. Image: SIMS Collection

What the studies have shown, is if we can control that [invasive species] early on and let the natural species establish, then it completely blocks out the introduced species. You then get a multiplier effect of restoring local species at the expense of potentially invasive species.