Seagrass Wrack Management Trial at Port Geographe

Published on 02 October 2018

The Department of Transport (DoT) and City of Busselton will be trialling actions this spring aimed at improving management of the seasonal accumulation of seagrass wrack at Port Geographe.

In the coming weeks machinery will be on standby, ready for when a significant westerly weather event occurs.  The machinery, in conjunction with the weather impact, will be used to break down the steep, compacted face of the seagrass wrack, closest to the seaward edge, to encourage sand movement and encourage early dispersal of accumulated material.

Wrack accumulations on the Western Beach have formed high and steep faces which are typically compact and more resistant to being re-mobilised by storm events. These steep wrack faces often extend into deeper water and impede beach sand migrating toward the Western Breakwater.

Port Geographe Segrass Wrack 2013-2018.jpg

Western Beach Aerial Photographs End of August / Beginning September 2013 to 2018

Machinery is planned to be used to assist in breaking down a section of the steep wrack face at the shoreline aimed at promoting the movement of sand from the west end of the seagrass wrack, to the area adjacent to the breakwater. With a greater volume of sand closer to the Western Breakwater there is improved opportunity for winter wrack accumulation to be shed more quickly in future years.

Any works will be targeted to take advantage of suitable weather and timed to minimise disruption to beach users and residents.

The work relies on a number of suitable late season weather events (which were effective in removing wrack in 2015 and 2016). Monitoring and review of the work may see adjustments being implemented as it is undertaken.  The trial aims to improve sand movement and accumulation, not completely remove the wrack. If favourable weather conditions for works do not occur and no natural movement of seagrass wrack takes place, other options will be assessed.

DoT and the City of Busselton are working together to improve the performance of the reconfiguration to achieve the long-term objective of optimising natural processes and reduce active management interventions. This approach applies to the harbour waterways, the entrance channel and the Wonnerup and Western Beach areas.

Enquiries may be directed to DoT’s Project Manager, Justin Fifield on 1300 660 815 or PortGeographe.Info@transport.wa.gov.au. Email enquiries may also be addressed to the City at portgeographe@busselton.wa.gov.au.