Mayor Greens responce 7 May 2010

Update Request – Lake Tabourie Condition

First of all, let me sincerely apologise for the delay in responding to your emails. I am advised that unfortunately Council staff requested to provide technical information inadvertently overlooked your correspondence.

Please find the following answers to the questions you asked in your emails dated 16 February 2010 and 24 February 2010, which have been provided by Council staff.

16 February 2010
Question1
Council in the last 12 months has been developing a Flood Study of Lake Tabourie including advanced modelling of berm heights under climate change conditions. This work will inform further studies and decisions related to entrance management. A paper on this topic has been delivered at the recent NSW Flood Conference. This pioneering work attracted the interest of other councils in charge of management of ICOLLs and is attached for your information. Also attached is the requested report from the University of Queensland on entrance opening procedures. This work will be continued during 2010.

Question 2
Council has 14 estuary systems under its management and is progressively developing and implementing estuary, flood and coastal management programs. The pace at which this happens is dependent on the availability of resources and state agencies funding priorities.

Question3
Opening the entrance will not raise the water levels. The current lake level is approximately 0.4m AHD which means the average lake level is above mean sea level. When the entrance is open, tidal exchange is limited due to friction losses along Tabourie Creek which connects the lake to the ocean. So whilst the lake level may increase at high tide this would be limited as the tidal range in the lake is only 0.28m. More importantly, the average lake level should the entrance be open, would more likely decrease to 0.15m AHD (based on historical records) as the lake slowly drains out to the sea. Historical records show that the average lake level when the entrance is closed is higher than the average lake level when the entrance is open.

Opening the entrance at low levels is unsustainable, the entrance would close back soon after being opened as there is not enough head in the lake to scour a large enough channel. Opening the entrance at low level would also create adverse effects on the lake ecology as demonstrated by the review of environmental factors undertaken by a specialist consultant. There is no requirement under the State Government Policy to open lake entrances to restore lake ecology. The fact that the lake is sometimes closed and sometimes opened is what makes its unique ecology. Opening the lake artificially would affect the natural lake ecology. There is no guarantee that the system will be flushed by opening the lake at low levels. The lake will be naturally flushed when a flood occurs but this does not necessarily result in better long-term water quality.

24 February 2010.
Question1
When property owners apply to Council to connect to the sewer, Council requires the septic tank to be de-commissioned, pumped-out by a licenced contractor, lime washed, a hole put in the base of the tank and the sides knocked in so that it does not hold water. Some property owners wish to keep the tank and convert it to a stormwater holding tank so the water can be used to water the garden. In this case, Council requires that the septic tank is de-commissioned, pumped-out by a licenced contractor and disinfected.

Question 2
Council has seven (7) sampling sites in Lake Tabourie.

Question 3
Samples are collected from all the sites at least four times a year and fortnightly during summer from two sites within the main body of the lake.

Question 4
Council does not test the bed of the lake.

Question 5
When the lake opens the ocean water will partially mix with estuarine water. The complexity of the interactions between different events including dilution, nutrient cycles, chemical and sedimentation processes, and nutrient inputs from catchment runoff does not necessarily ensure that the lake will be "cleaner" if it is opened.

Question 6
General lake health is reflected by a number of parameters, fish populations, foreshore vegetation, concentration of Chlorophyll a, nutrient concentration, etc.

Council is currently working with the NSW Department of Environment Climate Change and Water to monitor parameters that will be reflective of the overall condition of its lakes. These parameters will inform the NSW Natural Resources Monitoring, Evaluation and Reporting (MER) program. This program will provide information about natural resource condition and pressure on lake health. It is anticipated that report cards will be available to the community in 2010-11.

Question 7
The Flood Study will investigate the relationship between lake entrance, sand build up levels and flooding impact. It is anticipated that the results of the flood study will be presented to the community in June/July this year.

Question 8
Intervention on the sand shoals will be guided by the Lake Tabourie Flood Risk Management Study and Plan. This Study will start in 2010 and the community views on management options will be sought in 2011 during the investigation of different flood management options.

Question 9
Under the NSW Estuary Management Policy, local Councils are responsible for developing and implementing Estuary Management Plans through cooperation between the NSW Government, Local Government, Catchment Management Authorities, landholders and estuary users. These partners are members of Council’s Far South Natural Resources and Floodplain Management Committee which objective is to foster sustainable management of Shoalhaven’s natural resources including floodplains, coast and estuaries.

The Committee provides overall guidance for the management of natural resources including floodplain management, estuary management and coastal zone management in accordance with Federal, State and Local Government Policy and Legislative instruments.

Question 10
Low lake water levels are of natural occurrence and are part of the natural cycle for an ICOLL such as Tabourie Lake.


Question 11
To equitably manage a resource requires identification of the key ecological, social and economic values that people with an interest in the lake consider important and wish to see preserved into the future. Values can be important in a local, regional or national sense. The recent survey of the Lake Tabourie community sought to identify the values of the lake’s resources and the threats to the condition of the resources, so that objectives for future management of the lake can be developed. It is expected that the reviewed estuary management plan for Lake Tabourie will be publicly exhibited by the end of 2010. This review will have been informed by the recent survey and exhibited for comment.

Question 12
Council will not clear and maintain the entrance until such time that existing interim trigger levels for entrance opening are reached. It is not sustainable to open the entrance at low water levels similar to those currently experienced. Future information gathered through the flood risk management program may trigger a review of current entrance management practices as specified in the answer to question 8.

I trust these answers will assist in clarifying Council’s position on these issues.
Kind regards


Paul Green
Mayor