More than $5 million has been spent on dredging the Sunshine Coast’s main harbour entrance over the past five years in a bid to keep the critical waterway open amid increased shoaling.
The expense has been deemed essential for fishing, tourism and recreation industries, and the cost is likely to keep rising with more wild weather events, and with no permanent solution in sight.
The Mooloolah River mouth has been a subject of concern for years. The area has been dubbed “dangerous” and “risky” because of shoaling and breaking waves.
A Maritime Safety Queensland spokesperson said intermittent dredging was crucial.
“Without any dredging, the harbour entrance would become significantly blocked and would no longer service the harbour, meaning vessels would be severely restricted in their ability to enter or exit,” they said.
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“MSQ has a sediment transport model to predict when shoaling events are going to occur and can rapidly mobilise a local dredge contractor to clear the shoal when conditions allow.
“During these events, MSQ undertakes frequent hydrographic surveys to identify the best areas for navigation and communicates this information via Notice to Mariners.”
The most recent dredging campaign, conducted after severe weather in March, cost about $500,000.
The spokesperson said sand banks had become more problematic in recent years.
“Historically, shoaling events were quite infrequent with periods of up to 10 years between events,” the spokesperson said.
“However, the frequency of shoaling events has increased significantly in the last 15 years.”
The harbour entrance breakwaters were built in the late 1960s. Dredging has been done since the early 1970s. Major shoaling events in 2011-12 and 2022 required continuous dredging for long periods and had a significant impact on navigational access.
The state, through MSQ, is responsible for maintaining the harbour entrance, although Sunshine Coast Council has contributed some funds because some of the dredged sand is used to renourish Mooloolaba Beach.
Dredging is set to continue for the foreseeable future, in the face of extreme weather events associated with climate change and in the absence of more viable solutions.
“MSQ has undertaken extensive investigations and considered other options,” the spokesperson said.
“Feedback from the Stakeholder Reference Group, formed to consult on alternative shoal management options, was that capital works options were considered a last resort, given the potential negative coastal process impacts.”
It’s understood that MSQ is continuing to look at alternative shoal management options, including capital works such as a breakwater extension and sand bypassing systems.
There has been some success through a Western Channel Trial since 2022.
The ongoing initiative involves an adjustment to the dredging program to maintain a wide basin west of the entrance that provided boaties with a path when weather does not allow dredging for long periods.
The trial could be improved by a shoal monitoring pilot project using drones, which could provide more frequent information of shoal position.
Mooloolaba Fisheries general manager Paul Schenk said maintaining the harbour entrance was crucial.
“The dredging costs tonnes of money: it’s an expensive process,” he said.
“The dredge barge and boats are parked at our wharf and I see five or six guys go to the dredge and do what they’ve got to do.
“It will always be a constant, very expensive task to dredge but it has to be dredged for boats to consistently get through.
“The reality is they’ll need to keep dredging for the life of the passageway.
“It (the harbour entrance) is essential.
“It’s used regularly by dozens of (large) commercial boats (from The Spit) and many smaller commercial boats (from Mooloolaba Wharf and in the Kawana Canal).
“If you look at the agrifood business, seafood is worth a lot of money.”
Mr Schenk said the fishing industry complemented the local tourism and hospitality sector.
“People love seeing a real commercial hub – tuna boats and prawn boats coming in every day – and it supports all the restaurants along the strip and other ones that we supply to. It’s absolutely essential for local business.”
The river mouth is also used by tourism operators: for whale watching, diving and cruising and for recreational pursuits like jet-skiing, rowing and casual fishing.
Mr Schenk also said any suggestions of a revamp of the river entrance, including redirection, was “dreamland stuff”.
Meanwhile, the MSQ spokesperson urged boaties to be vigilant around the river mouth.
“The use of dredging and correct passage planning during dredging works has minimised the impact on commercial and tourism industries. However, like all coastal bars during heavy weather conditions, Mooloolah River bar can be extremely treacherous,” they said.
“Mariners are advised to check local conditions and ensure all safety precautions are in place before attempting to cross the Mooloolah River bar, especially a low water or at night.
“MSQ encourages boaties to check weather forecasts, tide charts and bar conditions before entering or exiting the harbour.
“Understanding vessel limitations, using the mandatory safety equipment required and ensuring all safety precautions are in place further reduces risks.
“With careful preparation and awareness, navigating the harbour can be done safely and effectively.”
