Autumn Estuary update
Estuaries are dynamic and often in a state of transition. This Autumn is a great example of an environmental zone that is in flux.
Across West Gippsland, estuaries are super important, working hard to soften the transition as rivers meet the sea. Many of the region’s estuaries open and close to the sea as conditions change and this is a natural and important process.
This Autumn, Bourne Creek, Merriman Creek, Kugerungmome/Powlett River and Wreck Creek Eastern Branch Estuaries are closed to the sea.
These closures are part of a natural process. During times of low river flows and moderate-high tides and swells they can stop flowing to the ocean because a sand bar forms across the entrance.
These estuary closures are good for the river because they provide calm, stable waters for fish to feed and breed, help the native plants and increase areas for birds to feed.
Under natural conditions, when an estuary is closed, water levels rise over time and eventually erode the sand bar – this usually happens with high rainfall in winter and spring. These natural openings are important because they reset the estuary and floodplain by flushing out nutrients and salt.
Estuary closures sometimes impact the environments and infrastructure we rely on like farmland, recreational assets, roads and bridges.
So, to keep things safe for us, an artificial opening may be needed.
Artificial openings are when a channel through the sand to reconnect the estuary to the ocean is undertaken manually. This usually happens during times of lower flows and are not as effective as a natural opening at flushing out nutrients and salt from the estuary.
West Gippsland CMA’s role is to manage the approvals if an artificial opening is needed. This task is complex, and something not done lightly. We do a thorough risk assessment to minimise possible impacts to the environmental, cultural, social and economic values of the estuary.
In the long-term, we are working with landholders, land managers and Traditional Owners towards a vision of reducing the need for artificial openings at sites along the Bunurong and Mullungdung coast (Kilcunda to Seaspray) and letting natural processes flow at sites like Kugerungmome/Powlett River that are loved and highly valued by the community.
At Kugerungmome/Powlett river estuary, we are working with partners to enable the mouth to open and close naturally which is the ultimate vision. If this vision can be achieved it will have many benefits, not just for the estuary and its floodplain but also for the socio-economic values such as tourism and recreational opportunities.
Powlett provides important wetland habitat
The Powlett River/Kugerungmome estuary on Bunurong Country near Kilcunda is a significant and ever-changing wetland that provides essential habitat for wildlife. In late August 2024, the river mouth closed to Bass Strait naturally and West Gippsland Catchment Management Authority (CMA) is monitoring the event.
The closure is a result of sustained large swells over the past weeks which deposited sand into the estuary entrance. Large ocean swells and low river flows allow the ocean to develop a sandbar at the mouth of an estuary eventually closing its connection to the ocean.
“Estuary closures provide critical habitat for many threatened species,” said West Gippsland CMA CEO, Martin Fuller.
“The Powlett River Estuary is one of many estuaries across the state that has recently closed its connection to the ocean”.
“Over the coming weeks, if the river mouth remains closed, we can expect to see water continue to nourish the wetlands,” explained Mr Fuller.
“This helps maintain the health of the wetland that surrounds the estuary”.
“The wetland provides important habitat and an abundance of food for many species of fish, birds and invertebrates that seek food and shelter, some of which are endangered.”
Mr Fuller explained that it is very important to support this natural process, otherwise the integrity of the surrounding wetland and the species it supports maybe jeopardised.
“There is a flow on effect when the river mouth closes,” continued Mr Fuller.
“Algae begins to grow which provides food for insects and fish. The calm waters then turn into a fish nursery and with the increase in fish and insects – birds flock to the wetlands to feed”.
“The environmental benefits of the estuary mouth closing cannot be overstated and if the mouth does open naturally, particularly as a result of increased water level height and freshwater river flows, it will trigger fish migration upstream and out to sea,” explained Mr Fuller.
West Gippsland CMA will monitor conditions and if required, the river mouth may need to be artificially opened. Decisions to open the estuary mouth are informed by the Estuary Entrance Management Support System (EEMSS) and additional data and information connected through onsite monitoring and stakeholder consultation.
“If it is decided that an artificial opening is required, it will only take place if it is deemed safe and sustainable. This requires a number of things to line up,” Mr Fuller explained.
In an effort to look for a long-term solution to address this issue, and alleviate the need for artificial estuary openings, West Gippsland CMA continues to work with landholders and other agency staff to explore options for the management of this land moving forward.
Opening of Bourne Creek, estuary
West Gippsland Catchment Management Authority (CMA) has approved an artificial opening of Bourne Creek estuary, Kilcunda to prevent potential flooding of the Bass Highway.
The estuary opening is scheduled for Tuesday 3 September 2024 and will be undertaken by Parks Victoria when it is safe to do so, under the guidance of West Gippsland CMA.
Bourne Creek estuary entrance closed naturally to the ocean last week after large swells deposited sand across the estuary entrance. Those same swells caused water levels in the creek to rise.
“It’s a careful balance. Estuary closures are natural events that provide many environmental benefits for birds, fish and the surrounding saltmarsh and wetlands. However, they also pose risks to surrounding assets by inundating farmland, cultural assets, roads and recreational infrastructure,” said West Gippsland CMA CEO Martin Fuller.
“Artificial openings are only used in conditions where it is unlikely that the estuary will naturally open to the ocean before flooding occurs, as is the current situation at Bourne Creek.”
“The CMA is responsible for monitoring the closure conditions, carrying out the risk assessment and making the decision to artificially open the estuary.
This decision has been informed through extensive monitoring, a thorough risk and feasibility assessment and in consultation with Parks Victoria and Department of Transport and Planning. The opening involves a small digger removing sand at the estuary opening at a carefully selected time to allow water to flow into the ocean. The CMA will continue to work with landholders and partners to enable the natural opening and closing of estuaries with minimal impact top roads and other important assets.
“Ultimately, we are committed to supporting the environmental benefits of natural water cycles and improving the condition of West Gippsland’s valuable river and estuaries in the long term,” said Mr Fuller.
A chat about estuaries on the shore of Powlett River/Kugerungmome with our Waterways Officer, Callum.
Our Waterways Officer, Callum Edwards, unlocks the language of estuaries and how we are working together to care for them. In this episode, Sally and Callum sit at the windy shore of Powlett River/Kugerungmome on Bunurong Country in South Gippsland and talk estuaries – what they are, the language around them and how we manage them.
About the podcast
About the podcast
Gippslandscapes is an occasional podcast, highlighting the many people doing great things caring for the environment and improving the landscapes of our region. Whether they are farmers, “townies” involved in Landcare, or just someone with a passion to make the region a better place.
Each episode will feature one person or group and they are available wherever you get your podcasts. All episodes are archived on Zen-cast and Apple Podcasts.
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