Hon Dave Kelly BA MLA

Hon Dave Kelly BA MLA

Minister for Water; Forestry; Youth

    Busselton flood defences boosted with $29 million upgrade to diversion drain

    1/09/2021 10:00 AM
    • Vasse Diversion Drain capacity increased by 33% as climate change makes extreme weather more likely
    • Upgrade designed to safely convey a 1-in-100-year flood event
    • $9.5 million local spend and more than 300 South-West workers employed
    • Extensive $3 million revegetation plan developed with 15 local stakeholder groups 

    Busselton's flood protection has been significantly enhanced with the official completion of the $29 million upgrade to the Vasse Diversion Drain, announced today by Water Minister Dave Kelly.


    Re-engineered to safely convey a 1-in-100-year flood, the 6.3 kilometre drain diverts the Vasse and Upper Sabina rivers to Geographe Bay. It is a critical component of Busselton's flood mitigation, as rainfall events become more severe due to climate change.


    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 essential 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.


    Comments attributed to Water Minister Dave Kelly:


    "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.


    "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.


    "I commend Water Corporation for taking this genuinely collaborative approach - a textbook example for similar projects."


    Comments attributed to South West Region MLC Jackie Jarvis:


    "This vital $29 million investment by the McGowan Government will bolster Busselton's flood defences for decades to come, in one of the most climate-impacted areas of the world.


    "Water Corporation's project has also been a welcome $9.5 million boost for the regional economy and has directly supported more than 300 local jobs.


    "And, with its key focus on environmental stewardship, it's been great seeing so many local people, passionate about the environment, contributing their time and expertise to this project."


    Minister's office - 6552 6100


    Vasse Diversion Drain upgrades fact file

    • Located in the City of Busselton, the Vasse Diversion Drain extends 6.3km from north of the Busselton Golf Course to the ocean at Geographe Bay. 
    • Diverts water from the Vasse and Sabina rivers to protect residential properties and the surrounding environment from the risk of flooding (1-in-100-year flood event).
    • Upgrade construction started November 2020 and included widening 5.5km of the drain and reconstruction of the levee banks; and reconstruction of the Vasse River diversion dam, including outlet and overflow structures and lower gauging station.
    • Other works included modifications to existing pedestrian bridges, and the installation of a second culvert to improve water quality in the Lower Vasse River.
    • Vasse Joint Venture, an arrangement between Westforce Construction and JWI Contractors, undertook the work on behalf of Water Corporation.
    • The project involved permanent clearing of 1.9ha of vegetation, reduced through careful planning and design.
    • A $3 million revegetation and offset plan was developed between Water Corporation,  Department of Water and Environmental Regulation, Tranen Revegetation Systems,  City of Busselton and Professor Kingsley Dixon:
      • More than 220,000 seedlings are being planted across 15ha of surrounding bushland to improve biodiversity and aid ecological restoration;
      • Revegetation work will take around 2-3 years and Water Corporation will manage the site for 10 years to meet its clearing offset requirements; and
      • WA fauna specialists Mike and Mandy Bamford assisted with the positioning of 88 fauna shelters and 15 rope bridges for western ringtail possums.
    • Aquatic ecology specialists Indo-Pacific Environmental, supported by OzFish volunteers, successfully relocated 37,000 protected Carter's freshwater mussels upstream, which will naturally repopulate the drain when they spawn.
    • The drain was originally constructed in the 1920s to divert the Vasse River to the west of the city. This involved building a diversion dam on the river and a 6km drain through to Geographe Bay, with dumped spoil from the excavation forming 'levee banks'.