FAQs

Burrill Lake

Burrill Lake includes the settlements of Dolphin Point, Burrill Lake Village, Bungalow Park and Kings Point. 

The catchment area is 78 km² and the lake waterbody has a surface area of 4 km². The main tributary of the lake system is Stony Creek which flows into the northern end of Burrill Lake.

Burrill Lake connects to the Tasman Sea through Burrill Inlet. The inlet is generally open to the sea, but there are some recorded periods of closure. Mechanical opening of the entrance by Council is managed through its Entrance Management Plan. 

Lake Conjola

Lake Conjola includes the settlements of Lake Conjola Village, Killarney, Conjola West, Fisherman’s Paradise and Berringer Lake. 

The catchment area is 145 km² and the main lake waterbody has a surface area of 4.3 km². The main tributaries of the lake system are Luncheon, Conjola, Gooloo and Bunnair Creeks which principally drain the large western section of Lake Conjola's catchment. 

The inlet channel to Lake Conjola from the Tasman Sea is approximately 3.5 km long and is subjected to periodic closures. The frequency of closure depends on the level of sand build-up at the entrance from oceanic forces versus the amount of catchment runoff and its ability to scour the inlet open. Mechanical opening of the entrance by Council is managed through its Entrance Management Plan.

Tabourie Lake

The Lake Tabourie Township is the only significant development in the area where most residences straddle Lemon Tree Creek. On the northern side of Tabourie Creek, at the outlet to the Tasman Sea, is the Lake Tabourie Tourist Park.

The catchment area is 46 km² and the lake system is mainly fed by Lucy King Creek, Munno Creek, Branderee Creek, and Lemon Tree Creek. The majority of Tabourie Lake is located upstream of Princes Highway Bridge, while the watercourse downstream of the bridge is generally referred to as Tabourie Creek.

The Tabourie Lake entrance is frequently closed to the sea by oceanic wave actions. Mechanical opening of the entrance by Council is managed through its
Entrance Management Plan.

A flood warning system is a set of connected activities designed to provide advice on potential flooding so people can take action to minimise impacts. The concept of the total flood warning system in Australia includes six basic elements:

• Monitoring and prediction: detecting environmental conditions that lead to flooding, and predicting river or lake levels during the flooding.
• Interpretation: identifying the impacts of the predicted flood levels on communities at risk in advance of the flooding.
• Message construction: devising the content of the message which will warn people of the impending flooding.
• Communication: distributing warning information in a timely fashion to people and organisations likely to be affected by the flooding.
• Protective response: generating appropriate and timely actions and behaviours from the agencies involved and from the threatened community.
• Review: examining the various aspects of the system with a view to improving its performance.

All six elements must be present and functionally integrated for the total flood warning system to be working effectively.

Additional information on flood warning systems can be found in the Australian Disaster Resilience Handbook Collection, Application of the Total Warning System to Flood.

No. There is no formal and site-specific flood warning system for Lake Conjola, Burrill Lake or Tabourie Lake. Council and NSW SES emergency response to flood events currently rely upon weather warnings from the Bureau of Meteorology (the Bureau) and rainfall and water level information from monitoring gauges in each of the catchments and surrounding areas. 

Lake Conjola, Burrill Lake and Tabourie Lake are ICOLLs and subject to flash flooding. Under the National Arrangements for Flood Forecasting and Warning (2018), the responsibility of flood warning in non-riverine, flash-flood environments lies with Council working in partnership with the NSW Government and other agencies. 

Riverine Flooding occurs when the rain-to-flood delay time is relatively high – typically more than six hours, but excludes flooding caused by elevated sea level, storm surge, flash floods, urban overland flow, or failure of any artificial infrastructure (dams or levees). The Bureau issues flood warning products for riverine flooding, which includes Flood Watch and Flood Warnings.

Flash Flooding typically occurs within six hours of the flood producing rainfall. Flash flooding can have high peak flows that do not last as long as riverine flooding. The Bureau issues flash flood warnings to a limited number of locations in NSW, which are delivered as Flood Watch or Flood Warning products. Advice related to storms that may cause flash flooding is available from the Bureau's Severe Weather and Thunderstorm Warnings.

Areas in each of these catchments are susceptible to flooding, placing property and lives at risk and causing disruption to businesses and populations. Previous floodplain risk management studies found that for a flood with 1% Annual Exceedance Probability (AEP), 183 properties are at risk of flooding above floor levels (in habitable buildings) in Lake Conjola, 318 properties in Burrill Lake and 42 properties in  Lake Tabourie. This risk is expected to increase into the future. 

In each of these catchments, previous floodplain risk management studies note the fundamental importance of implementing a flood warning system as one of the priority actions to reduce risk to life during flood events. Furthermore, this action was adopted for implementation in the respective floodplain risk management plans for these catchments. This project, is as such, progressing these Council adopted plans.

Flood warning systems also help emergency services, Council and community (including businesses) respond more proactively prior to a flood event by giving extra warning time with necessary information to make appropriate flood-safe decisions. 

More information about flood risk for your area, including interactive flood mapping and major flood-related projects can be found on Council’s webpage: https://www.shoalhaven.nsw.gov.au/For-Residents/Our-Environment/Flooding-Fire/Flood-Risk-in-the-Shoalhaven 

The primary benefits of a flood warning system are to inform those at risk of a potential flood hazard and to encourage them to undertake appropriate protective behaviour to keep them and others safe during a flood. Effective flood warnings enable emergency responders and community members to take proactive action to lessen flood impacts. Warnings have been linked to reductions in flood fatalities and to some extent flood damages (Haynes et al., 2017). Other benefits of flood warning include: more informed and proactive emergency response, improved flood warning to local businesses to help manage operations that are impacted by flooding, improved warning to local residents and road users to make safe decisions, more informed pre-flood entrance management, and encouraging ongoing improvements to resilience and safety during flooding. 

Due to the significance of effective flood warning services to communities, a number of key stakeholders collaborate during the design and delivery of these services to ensure they are effective. Key stakeholders include:

• Bureau of Metrology (the Bureau): historical and statutory responsibility of issuing warnings of weather conditions likely to cause flooding, as well as flood predictions and warning products. The Bureau owns and maintains a portion of the NSW gauge network.
• NSW State Emergency Service (NSW SES): the legislated agency responsible for emergency flood operations. The NSW SES are also legislated to deliver flood warnings through the Australian Warning System.
• NSW Department of Planning and Environment (DPE): provides financial support and technical advice to councils to investigate the potential for/installing new gauges/networks, and to develop new flood warning services. DPE owns and maintains a portion of the NSW gauge network east of the Great Dividing Range.
• Local Government (councils): determine flood risk and mitigation options within the respective Local Government Area (LGA), which is based on the development of Flood Studies and subsequent Floodplain Risk Management Studies and Plans. Flood risk mitigation options may include flood warning services.
• Community and Local Businesses: flood prone communities must be made ready to understand and act on flood warnings and floods themselves. Community engagement is critical to building and maintaining awareness of flooding and flood warning systems. This includes local residents, businesses, road users and visiting populations. 

Based on flood predictions, the NSW SES is responsible for issuing warning products to communities based on expected consequences from flooding. NSW SES issues warning products in-line with the Australian Warning System (AWS) which is a nationally consistent multi hazard system for emergency services to use when warning communities of expected consequences and relevant hazards. There are three types of warning messaging which include:

• Advice: issued when there is a heightened level of threat, and the community needs to stay up to date as the situation changes.
• Watch and Act: issued when conditions are changing, and the community needs to start taking action to protect themselves and their family.
• Emergency Warning: the highest level of warning. Issued when community may be in danger and need to take action immediately.

Each warning message has three components: Location + Hazard; Action Statement; and a Warning Level.

More information on the Australian Warning System can be found here: https://www.australianwarningsystem.com.au/

More information on NSW SES warning products can be found here: https://www.ses.nsw.gov.au/flood-resources/before-a-flood/be-aware/

ICOLL stands for Intermittently Closed and Open Lakes and Lagoons. ICOLLs are coastal lakes and lagoons that have dynamic entrance channels that close and open to the ocean for periods of time under natural processes. 

The frequency and duration of entrance closure differs between each ICOLL and is related to a number of factors that drive rates of sediment infill and scour of the entrance channel. These include tidal prism characteristics (i.e., the volume of water leaving an estuary during an outgoing tide), catchment rainfall, coastal processes including local wave and ocean conditions, as well as site-specific entrance factors.

According to entrance status records from 1916 to 2019, the Lake Conjola entrance was open for approximately 89% of the time and closed for the remaining 11% of the time (provided by Council, courtesy of Isabelle Ghetti Spreadsheets from Ken Dodimead).Tabourie Lake is more prone to entrance closure than Lake Conjola. Analysis of lake water level data extending from 1992 to 2017 was undertaken by Cardno (2019) and showed that the lake was open approximately 32% of the time during that period and closed for the remaining 68% of the time. 

Burrill Lake on the other hand typically maintains an open entrance for the majority of the time, however, can close on the odd occasion for extended periods (Peter Spurway & Associates Pty Ltd, 2008). Haines (2006) estimated that Burrill Lake entrance is open to the ocean approximately 98% of the time and closed the remaining 2% of the time. 

There are a number of factors that contribute to flooding in an ICOLL catchment. Some of the key factors include the amount of rainfall over the catchment, the capacity for the catchment to store floodwaters (for example in undeveloped floodplains and wetlands etc.), the condition of the entrance channel prior to a flood (e.g., open or closed) and the prevailing ocean conditions (tides, waves etc.). It is a complex interaction of these factors that result in the level of flooding for a given event. 

More information about flood behaviour can be found in the latest Floodplain Risk Management Studies and Plans for each of the catchments via Council’s webpage: https://www.shoalhaven.nsw.gov.au/For-Residents/Our-Environment/Flooding-Fire/Flood-Risk-in-the-Shoalhaven

A flood warning system predicts flooding by inputting available flood monitoring and forecast information into a real-time predictive model to estimate flood levels. Key inputs to predicting a flood in an ICOLL include: 

• Prevailing and forecast rainfall from the Bureau
• Current water levels in the catchment from gauges 
• Catchment conditions (i.e., how wet or dry the catchment is from previous rainfall)
• Latest entrance channel information and estimated flood scour
• Prevailing and forecast ocean conditions (tides, waves etc) 

These inputs are used by a flood model that is run continuously in real-time to predict flooding in an ICOLL catchment. The flood model is setup with its accuracy checked against past events. 

Information from the flood model is then passed on to SES to help inform decision-making prior to a flood event and trigger warnings issued to the community. 

Flood warning messages would generally be sent via a range of mechanisms such as SMS, radio, door knocking (where possible), phone calls, social media, SES website, Council’s Disaster Dashboard webpage and Hazards Near Me app. 

A flood warning system should utilise a variety of mechanisms to communicate warning messaging to allow for redundancy, varying demographics (differ degrees of familiarity with technologies) and potential communication line failures (e.g., phone reception issues, power outages) during a flood event.

Importantly, communication formats for flood warning are to be clear, concise and consistent with the Australian Warning System format. 

The scoping study so far has developed a number of preliminary flood warning system options for Lake Conjola, Burrill Lake and Tabourie Lake. Three preliminary flood warning system options were developed for each catchment and include:

1. Predictive flood warning and decision support (utilising present gauge network)
2. Predictive flood warning and decision support with priority 1 gauge installation works
3. Predictive flood warning and decision support with priority 2 gauge installation works

Design components included in each of these options are outlined in the tables provided in the document library on this Get Involved webpage. Under this approach, predictive flood warning and decision support (Option 1) is to provide the minimal basis for flood warning in each catchment and additional priority gauging is undertaken as required to support more robust flood warning operation. The flood warning system is expected to provide approximately 12 - 24 hours of warning time at Lake Conjola and Burrill Lake, and 6-12 hours of warning at Tabourie Lake. 

A preferred flood warning system option for each catchment is to be selected in consultation with Council, the NSW State Emergency Service, the Bureau of Meteorology, Department of Planning and Environment, Environment and Heritage Group (DPE EHG), and the community. Detailed development of a preferred flood warning system option for each catchment is to be undertaken in subsequent stages. 

The next phase of the project will involve the detailed development of a preferred flood warning system option for each catchment. This will include developing detailed flood warning system design, draft flood warning system owner’s manual, key inclusions for the NSW SES Local Flood Plan, draft community education and awareness program (to be confirmed) and draft scope of works for implementation of the warning system.

Council will then look for funding opportunities for the implementation and ongoing maintenance of the flood warning system.