Dredging
What is dredging?
Dredging is an essential process aimed at maintaining navigable waterways. It involves the removal and relocation of built-up sediment from channels to ensure that water routes remain safe and accessible for residential, commercial and recreational users. The program is expected to move 10-15,000 cubic meters of sand and sediment.
Benefits of dredging
Dredging keeps channels safe for movement, allowing our community to explore our waterways. It also supports the flow of sand towards our northern beaches.
What to expect during dredging
When dredging is taking place, you may see dredging vessels and machinery along the waterways and foreshore areas. A cutter suction dredge moves across the bottom of the channel, sucking up sediment and pumping it through a pipeline to the disposal site.
Some low-level noise from boat engines and minor disruptions to boat traffic may occur during this time. Should air get in, the pipeline may float to the surface. For safety, boat users should follow navigational lights and signage and keep an eye on the water to avoid any collisions.
A dark-coloured plume is often present in the water during the dredging process. This is floating fine sediment removed from the channel floor. Once the work is complete, the plume normally disappears within 24 hours. Sediment pumped to the disposal site will return to a light colour after a few days of sun exposure.
Continuous monitoring is conducted throughout the dredging period to ensure no detrimental effects on water quality
Sand bypassing
The Department of Transport conducts the sand bypassing program each year at the Dawesville Cut and Mandurah Ocean Entrance channels. This sand bypassing allows safe navigation around these entrance channels while also allowing the natural flow of sediment to continue along the coast.
The City is committed to protecting Mandurah’s beautiful waterways.
It is important that the foreshores near these waterways are developed and managed effectively. Managing our foreshores;
- Ensures the protection of natural values that help to filter pollutants from our urban development and activities
- Provides habitats for our local and visiting international waterbirds
- Provides a range of recreational activities for our community
- Enables ongoing asset management and monitoring.
Mandurah boasts numerous waterways and wetlands, some of which are internationally recognised and protected, through the Ramsar Convention on Wetlands, Japan Australia (JAMBA) and the China Australia Migratory Bird Agreements (CAMBA).
Benefit of wetlands
Although these wetlands, depending on their location may not have water covering the entire soil all year, are very important to our natural environment, providing benefits such as:
- The control flooding that help protect our coastal areas by slowing down the movement of waters
- Filtering waste and pollutants and improving the quality of water
- Conservation of biological diversity
- Providing habitat for a great diversity of plant and animal species
- Provision of economic and recreation value from recreational fishing to tourism
- Hold important social and cultural values to members of our community.
Wetlands in Mandurah
- Peel-Yalgorup System (Peel Inlet and Harvey Estuary)
- Lake Clifton
- Lake Goergrup
- Creery Wetlands
- Hexam Close
- Samphire Cove
- Lower Serpentine
- Murray River
With an estimated 80 percent of wetlands on the Swan Coastal Plain having been cleared, filled, drained or otherwise destroyed since European settlement, the City’ Foreshore Rehabilitation Project will help minimise our impact, and enable the protection and rehabilitation of these valuable waterways.
Koi Carp (Cyprinus carpio) and Goldfish (Carassius auratus) are popular, colourful fish that many people keep in ponds and aquariums. While they may be common, they are not native to Western Australia's waterways and the presence of these invasive species impacts our beautiful natural environment.
Koi Carp and Goldfish have been introduced to Western Australia in two main ways:
- Deliberate releases: Many people release these fish into local waterways when they no longer want them as pets.
- Escapes from ponds or fish farms: Some Koi Carp escape from fish farms and enter natural water systems.
Impact on our wetlands and native species:
- Koi Carp and Goldfish are not native to Western Australia. They reproduce quickly, which disrupts local ecosystems and makes it hard for native fish species to survive.
- In the south-west of Western Australia, 82% of fish species are unique and 55% are endangered. Koi Carp and Goldfish threaten these native fish by competing for food and damaging their habitats. They also eat their eggs and young, which impacts the ability of these native species to maintain their populations.
- Koi Carp have a unique way of feeding. They suck sediment from the bottom of the water and filter it through their gills. This feeding method damages the environment by uprooting plants and stirring up sediments, which leads to a loss of habitat for native fish and reduces water clarity. This stops light from reaching underwater plants and can affect native fish that rely on clear water for visual hunting.
- Koi Carp breed very quickly. A single large female can easily carry up to 1 million eggs, This rapid breeding makes it very hard to get rid of them once they establish a population.
- Both Koi Carp and Goldfish can carry diseases, which can impact native fish species.
How you can help:
- Don't feed fish in local lakes and wetlands. Feeding can encourage the growth of feral fish populations like Koi Carp and Goldfish, making the problem worse. It can also lead to poor water quality.
- Never release Koi Carp, Goldfish, or any other ornamental fish into local lakes, rivers, wetlands or even drains and stormwater sumps. This introduces these harmful, invasive species into our natural areas and will negatively impact native ecosystems.
- If you catch Koi Carp or Goldfish, please dispose of them humanely. Do not release them back into the water.
By managing Koi Carp and Goldfish in our urban wetlands, we can better support our native fish species.
