Plan shows dredging as government responsibility
The Coastal Zone Management Plan for the Brisbane Water Estuary, finalised in 2012, lists periodic dredging of the navigation channel off Ettalong as a NSW Government responsibility.
This fact was drawn to the attention of elected Councillors when staff responded, on July 23, to a question on notice asked by Cr Troy Marquart at the Council's May 14 meeting.
"Is the channel dredging plan currently being used by Central Coast Council to create the required scope of works to maintain and/or remedy the Ettalong Channel issue based upon all the points noted within the Brisbane Waters Coastal Zone Management Plan which was previously adopted by the former Gosford Council in 2012?" Cr Marquart had asked.
The staff response to the July 23 meeting stated that "Action number W18 in Council's certified Coastal Zone Management Plan for Brisbane Water Estuary states: 'Periodically dredge the navigation channel up to 50,000 cubic metres in the Estuary entrance to ensure safe navigation'."
The staff report went on to say, "This action lists the NSW Government as having 'Primary Responsibility' for this work, and assumes that it would need to be periodically re-done every 5 years.
"Whilst an application for grant funding under the Rescue the Waterways program was submitted by Council, as resolved by the Council, it has no plans to undertake any dredging while that application has been determined."
The Coastal Zone Management Plan for Brisbane Water Estuary was signed off by the former Gosford Council in July 2012 and can still be found on Council's website.
It does not appear to have been superseded by any more recent management plan, however, its recommendations in relation to periodic dredging do not appear to have been implemented for the past six years.
It was prepared with financial assistance from the NSW Office of Environment and Heritage and under the NSW Coastal Management Process and in accordance with the NSW Rivers and Estuaries Policy.
According to the plan, it applies to areas including "from the channel connecting the estuary to Broken Bay at the eastern end of Ocean Beach in the south."
The plan's purpose was stated as "to manage and monitor ecosystem health and sustainable human usage of the estuary".
"It is therefore concerned with regularly occurring, day to day or seasonal processes that impact on ecosystem function.
The plan was recommended for detailed review once in every five to 10 years, which means a comprehensive review is due.
The issue of channel dredging falls within actions for Zone 6, described as "The Entrance Reach, including Booker Bay, Ettalong Beach, Lobster Beach, Wagstaff Point, Half Tide Rocks, Pretty Beach, Hardy's Bay and Rileys Bay".
In particular, Action W18: Periodically dredge the navigation channel, said: "Navigation through the entrance to the estuary can at times be difficult due to the propagation of a flood tide delta.
"The navigation channel markers are periodically relocated by NSW Maritime as required, but navigation can become difficult due to the strong currents in this region.
"This leads to issues with boating safety and access can be restricted for some tidal conditions.
"The community is also concerned that sedimentation at the entrance has impacts on the tidal flushing of the estuary upstream of this point, and also that tidal velocity in the main channels decreases resulting in reduced scour, thereby exacerbating the sedimentation issues throughout the channels in the estuary.
"Reference is made to linked Actions R09 and W28, which relate to the need to obtain regular hydrosurvey and potential for beach nourishment with the dredge spoils (respectively).
"It is understood that the propagation of these flood tide shoals is an ongoing process and therefore regular maintenance dredging of the entrance channel would be required.
"There are a number of dredging scenarios available that may achieve the action objectives.
"The concept details for this action are for a generic dredging scenario involving the removal of approximately 50,000 cubic metres of material from the entrance channel, although the optimal volume to be dredged is highly dependent upon the chosen dredge campaign.
"Furthermore, it is noted that the cost of implementation is highly dependent upon the volume dredged.
"The implementation process is as follows: Conduct hydrosurvey of the area of investigation.
"In consultation with the community and OEH, consider the navigation requirements and the desired channel configurations.
"Consider constraints (e.g. sediment quality) and opportunities (potential to link with nourishment works); develop concept options; conduct modelling of the concept options to assess the sustainability of the option; and identify a suitable disposal site for the dredge spoils."
Once those steps were completed, the plan stated that a cost-benefit analysis was to be completed, a preferred option selected and necessary environmental approvals, permits and licences obtained.
A contractor was then to be engaged to undertake the work followed by a post-dredge survey.
The plan said the Council needed to assume the dredging would need to be redone every five years on average.
It was given a preliminary capital cost estimate of $750,000 with an ongoing or recurrent cost of $125,000.
SOURCE:
Central Coast Council agenda 5.2, 23 Jul 2018
Website, 23 Jul 2018
s.centralcoast.nsw.gov.au/environment-and-waste/environmental-management-and-planning/estuaries/estuary-management-planning