Busselton flood defences have been boosted with the completion of a $29 million upgrade to the Vasse Diversion Drain increasing its capacity by 33 per cent.
As climate change makes extreme weather events more likely the upgrade was designed to handle a 1-in-100 year flood event.
The 6.3 kilometre drain diverts the Vasse and Upper Sabina rivers from the Busselton Golf Course to Geographe Bay.
It is a critical component of Busselton's flood mitigation, as rainfall events become more severe.
To increase the drain's capacity by a third, Water Corporation's project involved widening 5.5km of the channel and reconstructing the levee banks, originally built in the 1920s.
The diversion dam was also re-engineered, including outlet and overflow structures, and a pedestrian bridge extended to span the wider channel.
In addition to allowing greater control of the flows, the upgrades assist with water quality management in the Lower Vasse River, helping improve the health of the waterway.
Completed on time and under budget by head contractor Vasse Joint Venture - an arrangement between Westforce Construction and JWI Contractors - the project created more than 300 local jobs, including 10 apprentices, and employing three Aboriginal subcontractors.
In total, it invested around $9.5 million in the South-West - more than double the original target.
Several specialists, including world-renowned restoration ecologist Professor Kingsley Dixon, and 15 local environmental groups assisted Water Corporation and Department of Water and Environmental Regulation to develop an extensive $3 million, 10-year revegetation plan.
As part of this plan, more than 220,000 seedlings are being planted across 15 hectares of the surrounding area over the next two to three years to improve local biodiversity.
In addition, 88 fauna shelters and 15 rope bridges for western ringtail possums have been installed, accompanied by educational signage.
Prior to commencement, not-for-profit organisation OzFish assisted Water Corporation contractor Indo-Pacific Environmental with the relocation upstream of 37,000 protected Carter's freshwater mussels found in the drain.
Water Corporation will unveil a public artwork later this year under its Splash of Colour program to thank the Busselton community for supporting the project.
Water Minister Dave Kelly was in Bussleton to acknowledge completion of the work, saying without this critical upgrade, Busselton would be exposed to the ever increasing risk of severe flooding due to climate change, which is causing more extreme and unpredictable rainfall events.
"This year's unusually heavy winter rains have been something of a test for the newly upgraded drain, which has been designed to safely convey a 1-in-100-year flood," he said.
"Water Corporation and Department of Water and Environmental Regulation consulted with 15 local environmental groups to develop an impressive $3 million revegetation plan for the surrounding bushland.
"It will not only offset project vegetation clearing and improve the community experience of the area but also enhance its ecological function."
City of Busselton mayor Grant Henley said many historical photos of Busselton featured flooding events, demonstrating a long and complex history.
