Arno Bay Marina Breakwater Extension and Upgrade

The challenge

Arno Bay Marina is the working harbour for this part of the Eyre Peninsula coast, used by commercial aquaculture vessels, fishers and recreational boat owners. Waves reaching the boat ramp made launching and retrieval difficult in rougher conditions, and an ageing southern breakwater and gradual sediment build-up in the entrance were limiting how well the marina could serve the vessels that depend on it. The District Council of Cleve engaged Magryn to work out what could realistically be done and to carry the preferred option through to detailed design.

Our approach

We started with a clear picture of the site: the coastal conditions, the state of the existing breakwater and how the entrance had changed over time. Coastal modelling showed how waves reach the marina and allowed each concept to be compared on its performance, not on judgement alone. Design decisions were set against the conditions the structure will face over its life, including sea level rise. Council and the operators working out of the marina stayed involved throughout, which kept the preferred option practical for the people who use it.

The outcome

The detailed design upgrades and extends the southern breakwater to give calmer water for boat ramp users and the vessels that shelter in the marina, while keeping the entrance safe to navigate. It also gives Council a clear basis for planning ongoing sand management. The result is a more resilient marina, with a structure that should need far less repair over time.