Dredging Impacts

Dredging Timeline

  • Dredging at the entrance has been a regular event since the opening of the artificial and permanent canal at Lakes Entrance in 1889. The depth of the entrance during the past 100+ years has varied though it was programmed to be maintained to a depth of approximately 2.5m to cater for the local fishing fleet.
  • In 2001 the Lakes Entrance Chamber of Commerce, Gippsland Ports and East Gippsland Shire agreed to apply for Federal funding to investigate the development of Lakes Entrance as a deep sea port.
  • The application highlighted the need for a deeper entrance and stated “The channel depth of 2.5 metres prevents large craft from accessing the lakes and servicing the off shore oil/gas facilities”.
  • The application went further and stated, “Within a 3-4 year period the channel could be cut to 6.0 metres for access of vessels with drafts of 5.5 metres”.
  • In August 2001, marine consultant Gerry Byrne, Technical Specialist-Port Planning and Coastal Engineering was retained by Gippsland Ports to advise on providing access for vessels of 50 to 90 metres in length and draft of 5 to 6 metres to the port of Lakes Entrance.  He advised that “the entrance would need to be 7 metres deep, and if the entrance depth was increased artificially it would quickly silt up to its stable depth of 3 to 4 metres at low tide”. Further he advised that “the deepened entrance would also change the salinity intrusion into the lakes”.
  • In 2004, B Martin a previous Gippsland Ports manager was retained as a consultant on the Sand Management Study and reported, “It is considered entirely feasible to maintain a channel deeper than the suggested theoretical minimum of 3 metres”. Even so the recommendation is to first establish a reliable, safe and sustainable channel of 3 metres. A target depth rarely achieved”.
  • Gippsland Ports June 2007 Quarterly Report (Issue 6) refers to the dredging “trial” being programmed to commence in March 2008 and tenders for dredging being  advertised in July 2007. This was prior to Gippsland Ports applying for a dredging permit late in 2007.
  • A dredging contract was signed with a New Zealand firm in November 2007 with a commencement date of March 2008.
  • The Victorian Planning Minister and the Federal Environment Minister signed off on the “trial’ dredging without the need for an Environmental Effects Statement (EES). There simply wasn’t time for an EES as was demonstrated by environmental consultants John Kowarsky & Associates in February 2004 when they advised Gippsland Ports that an EES could take 12 months. The consultancy further advised that the Gippsland Boating Coastal Action Plan stated the following in regards to the Gippsland Lakes, “Any moves to deepen or widen the entrance would have to be preceded by extensive environmental, engineering and economic studies on the effects of the increased water flows on the rest of the lakes”.
  • The  dredger Pelican departed New Zealand on 16 Feb 2008 prior to Gippsland Ports receiving the dredging permit on the 18 Feb 2008. The total approval process took only 3 months.
  • The dredger Pelican excavated the entrance down to 6 metres and deepened the inner feeder channels. This resulted in the entrance not only being increased in cross-sectional area but the tidal flow speed through the entrance was greatly increased thus dramatically increasing the quantity of ocean water entering the lakes per tide change (tidal prism).
  •  GHD consultants reported that “between 2007 and Feb 2010, the average level of the entrance has been at -4.0 and -5.0 CD for 80% of the time“.
  • The 2007 flood deeply scoured the entrance and trial and maintenance dredging post 2007 has annually excavated the entrance down to around 6 metres. GHD make no reference to the fact that prior to 2007 the dredger April Hamer had difficulty in maintaining an entrance at 3 metres deep (Source: B Martin).
  • Gippsland Ports did not have a survey team capable of monitoring the entrance profile until 2007.

Dredging Impacts (Salinity Increase Post March 2008)

  • The entrance is now being maintained deeper than at any time in history. The width of the entrance is fixed at 80 metres between abutments but the increased depth (post April Hamer dredging) means that the cross-sectional area of the entrance has been almost doubled.
  • On 17 August 2011 GHD reported that, “changes to the entrance capacity can alter the volume of salt water flowing into the system”. Further they reported “the absence of detailed current velocity measurement through the entrance to calculate the tidal prism”.
  • Before the 2008 dredge, tidal flow speeds through the entrance were in the order of 2.5 knots. Fishermen and other boat users now report tidal speeds of around 6 knots, making the entrance more difficult to navigate and increasing the risk of a maritime safety incident.
  • Monthly Environment Protection Authority water quality monitoring and testing demonstrates a large increase in surface water salinity immediately following the 2008 dredging. High surface water salinity levels were maintained for the next two years without a freshwater respite and resulted in the die-back of fringing vegetation and massive bank erosion.
  • GEG scientific research has also found an increase in salinity at various points throughout the lakes.
  • In 1980, Geoffrey King of the Department of Minerals and Energy (Victoria) published a paper in the Royal Society of Victoria titled Tidal Scour in the Gippsland Lakes. He demonstrated that a flood tide introduced saline ocean water into the lakes but the return ebb tide discharged fresh/brackish water from the surface of the lakes to the ocean forcing the entrance to the sea to act as a salt pump.