Estuary Projects

The City of Mandurah undertakes projects to improve the ecological character of its foreshore reserves along the Peel Inlet and Harvey Estuary. Many of these projects are aimed at improving the fringing vegetation along the estuary. Fringing vegetation is the band of native plants which surround a water body and are directly affected by the water. Much of the dense belt of fringing vegetation around the western side of the Peel-Harvey estuary has been cleared for housing and recreation. To aid in the restoration of this vegetation weed control, formalising access to the estuary and revegetation is undertaken. Bank stabilisation is sometimes also needed to help vegetation combat the erosive nature of the water while it is establishing.

A range of projects are prioritised, planned and implemented based on the information in the Lower Serpentine River Action Plan.

This includes ‘Unofficial Bird Sanctuary’, or Reach 15 in the River Action Plan, a reserve located at the end of John Street in Nairns. This reserve has both an estuary and river foreshore as it is on the Serpentine river mouth and is an important feeding ground for migratory birds. As such revegetation and access control has been implemented over the past three years in the reserve in partnership with Peel TAFE. TAFE Conservation and Land Management students are able to gain hands-on experience in project planning, weed control and revegetation while helping the City of Mandurah manage this important area.

Other projects include revegetation of foreshore reserves to increase the width of fringing vegetation, erosion control along section of riverbank, upgrading of storm water swales to retain and treat water before it drains into the river and weed control to ensure that introduced plants do not out compete native vegetation.

Stabilisation at Reserve 34177 
One-hundred and fifty metres of baffle boards were constructed and installed along the foreshore in front of Lot 9 along the shoreline of Reserve 34177 with the help of Green Corps and the Department of Water.

Baffle boards are designed to reduce the erosive forces of wave action and tidal movement and encourage soil to build up along the shoreline. They allow water to pass through them at a reduced velocity and encourage soil held in the water to accrete. This provides a fairly stable environment encouraging reeds and sedges to become established (naturally or assisted) and eventually take control of site stability. Once vegetation has taken control, the baffle boards can then be removed.

The Mandurah inlet foreshore in front of the Waterside canals in Dudley Park is a popular recreation foreshore reserve. In the year 2000 the City of Mandurah advertised the draft Waterside Foreshore Reserve Concept Plan to upgrade the reserve. Following an extensive public consultation process the plan was approved.

This plan set out recreational improvements such as the construction of a dual use path, BBQ, seating, erosion control and the planting of shade trees. The Concept Plan also allowed for the area between the new path and estuary to be rehabilitated for foreshore conservation by removing grass and replanting native understorey species and sedges to improve habitat, bank stability and water quality.

Between the years 2000 and 2005 implementation commenced on the recreational features of the plan for example path, grass, toilets and shade trees. In 2005 the planned foreshore rehabilitation project began in partnership with Challenger TAFE. Stages 1 and 2 of the project have now been implemented which has seen over half of the foreshore area remediated through grass removal, ripping, mulched, weed spraying and native seedling planting with the help of TAFE students, Greencorps and the City’s Bushland Conservation team. Approximately 1000 understorey plants and 6000 sedges and rushes have been successfully planted with great survival rates.

The last stage of the rehabilitation project will be implemented in 2010.  Some modifications have been made to this stage as a result of experiences gained over the life of the project and from feedback from local residents.

The City of Mandurah’s foreshore reserve along the Harvey Estuary is undergoing an upgrade program to widen fringing vegetation and target significant bushland weeds. Much of the dense belt of fringing vegetation around the western side of the Peel-Harvey estuary has been cleared for housing and recreation.

The Southern Progress Association and the then Waters and Rivers Commission started reinstating native sedges with a planting program along the western foreshore of the Harvey Estuary in the 1990s which has been successful in maintaining bank integrity and habitat. This is however a narrow buffer zone of sometimes only two metres in width.

With this base to work with, further renewal is aimed at widening this buffer of fringing vegetation to provide a more diverse habitat for wildlife, improved stormwater filtering, foreshore stabilisation and repair of ecological processes. For these reasons fringing vegetation is perhaps the most biologically productive part of the estuary. Increasing tidal ranges and wave action due to the Dawesville Cut has resulted in tree deaths and shoreline erosion problems that are more severe in places where only a narrow band of fringing vegetation remains.

The Western Estuary Foreshore Upgrade project is managed by the City’s Foreshore Rehabilitation Officer. Grass and weeds are removed from between the water and the pathway along the estuary and the area is then mulched and planted. Stage 1, just south of the Dawesville Cut along Estuary Drive, was planted in winter 2008 and has achieved a good success rate. Stage 2 just south of the first site was planted in winter 2009 by volunteers from the City of Mandurah staff. Both of these areas have been planned to ensure that existing access to the estuary is maintained.

Many garden escapees are impacting heavily on this narrow band of vegetation with morning glory (Ipomea indica), garden nasturtium (Tropaeolum majus) along with bridal creeper (Asparagus asparagoides) smothering native plants. Bridal creeper and other weeds will be targeted along the length of the foreshore reserve with a coordinated weed control strategy that aims to reduce these threats.