- future land use decisions;
- how we design and maintain roads and drainage systems;
- what is required to make buildings safe and durable;
- emergency response during floods and storm events;
- how we manage erosion and beach recession; and
- how we continue to enjoy our unique
lakeside lifestyle; and how we keep the lake clean and
- Acknowledges that risks are location specific and are best addressed at the local level.
- Recognises that being prepared requires input from landowners, business owners, residents, special interest groups and organisations, Council, and state government agencies.
- Is timed so the actions are implemented to respond to increases in risk, as they are required.
- Identifies the criteria for a successful outcome (economic, social, environmental).
- Provides a level of certainty for decision-making by the public, Council and others, yet is flexible enough to change with changing information.
completing a survey;
marking areas on the interactive map;
sharing your flooding and inundation experiences;
submitting your photos;
suggesting an idea on the ideas wall;
answering a quick question or poll;
asking a question; and
signing up to our project newsletter.
Heavy rainfall in the catchment of creeks, such as Dora Creek and Cockle Creek, can cause run-off that raises the water level in the lake. This is added to by rainfall on the lake itself.
High ocean levels caused by high tides and storm surge enter the lake via Swansea Channel and cause lake levels to rise higher than usual.
1% AEP (Annual Exceedance Probability) – the preferred way
1:100 year flood;
100 year ARI (Average Recurrence Interval);
What is a Local Adaptation Plan?
Local Adaptation Plans are location-specific plans developed with the community that guide:
The City’s first local adaptation plan was prepared with the communities of Marks Point and Belmont South. The combined Pelican, Blacksmiths, Swansea and surrounds is the second local adaptation plan currently being developed with the community. View these relatied projects online at shape.lakemac.com.au/future-flood-planning and shape.lakemac.com.au/futurepelicanblacksmiths.
What is local adaptation planning and why is the City doing it?
Adaptation planning identifies actions that Council, in conjunction with our community, can take to respond to a change in climate and prepare for projected increases in lake levels and lake flooding over a long period of time.
These actions are designed to reduce these impacts and ensure our City is resilient and continues to prosper. Adaptation planning is about understanding what options are available and deciding which ones are best at a local level for our City.
Adaptation plans will guide future decisions, such as how we design and maintain roads and drainage systems, how to make buildings safe and durable, and how we manage erosion and maintain a healthy lake.
What is the Probabilistic Hazard and Damages Assessment?
Council engaged Salients Pty Ltd to undertake a probabilistic hazard and damages assessment to examine the current and future combined flooding and tidal inundation risks (and damages) for Pelican, Blacksmiths and Swansea.
The study will form the basis of a cost benefit and distribution analysis.
How can I participate in the online consultations?
Council encourages all community members living and working in Swansea to share their experiences and ideas online to help us prepare for the future and develop the Swansea Local Adaptation plan.
You can participate online on this Shape Lake Mac project site, Adapting Swansea (shape.lakemac.com.au/adapting-swansea) by:
Should I sign up to Shape Lake Mac?
We are interested in hearing from our community on a range of projects. If you would like to stay up to date with this project and find out more about others we are working on, sign up and have your say!
If you have not previously participated simply click on the "Register" button at the top right hand of the page, when prompted create a SCREENNAME (Note: your comments will appear under your screenname and you can comment anonymously through a screenname of your choice) create a PASSWORD of your choice provide a valid email address, your age, gender and the location in which you live.
If you have previously participated simply click on the "Sign In" function located on the right hand side of the top tool bar.
To participate in other parts of the project, such as attending an information session or workshop please see the 'key events' page of the website
Is my privacy protected when participating online?
Yes! Your privacy is absolutely protected and Council and will only use your email to contact you with updates and to invite you to participate in consultations.Your email address and any other information provided by you will not be distributed to any third party or used for any other purpose. We do not ask for your personal details or require them at any time as part of your participation.
What causes the lake to flood?
Flooding in the lake can come from two sources:
It is when these two eventshappen at the same time, such as during the June 2007 ‘Pasha Bulker’ storm, that we get the most severe floods. In high winds, lake waves can make flooding around the lake foreshore even worse.
What difference will sea level rise make to floods?
As ocean levels rise, the level of Lake Macquarie will rise by about the same amount. Current predictions by scientific experts are that sea levels on the east coast of Australia will rise by 0.4 metres by 2050, and by 0.9 metres by 2100. So, if a flood occurs in 2050, it will be about 0.4 metres higher than if the same flood occurred today. The lake flood study shows that the increase in flood height is actually a little less than the underlying increase in ocean and lake levels as a result of sea level rise.
What if sea level rise predictions are wrong?
The current projected sea level rises used by Council are based on the best available scientific advice, assuming continued high levels of global carbon emissions. As the science is updated and improved, or as emissions scenarios change, the predictions will be reviewed. Actual sea level rise is now being measured and tracked, so the predictions can be tested against actual measurements. The Lake Macquarie Waterway Flood Study and Plan (2012) will be reviewed regularly (at least every five years) to incorporate the latest scientific measurements and predictions.
Why don’t we just make Swansea Channel bigger to let the flood water out faster?
There is a common belief that making Swansea Channel bigger will reduce flood levels by allowing the lake to drain more quickly. This would be true if the lake drained into an empty basin, but it drains into the Pacific Ocean. The channel lets water into the lake from the ocean, as well as letting flood water out.
Hydrological (water) studies show that for most floods, up to the extreme 1:200 year flood, ocean high-tide levels are higher than the peak lake flood level. If the channel was larger, it would allow more ocean water in at high tide, increasing peak flood levels, not reducing them. So making the channel larger may actually increase flood peaks for the most frequent floods. It would only have some advantage for the rare but extreme 1:500 year flood and ‘probable maximum floods’. A larger channel will also increase tidal influence in the lake in non-flood times, increasing the tidal range, and raising high tide levels. This would increase the effects of sea level rise on the lake foreshore, although only slightly.
What is the worst flood recorded in Lake Macquarie?
The highest flood recorded in the lake was in 1949, when the level reached 1.25 metres AHD. The June 2007 ‘Pasha Bulker’ flood was only the fourth highest, reaching 1.05 metres AHD. A severe flood considered to occur on average once in a hundred years (1:100 year flood) and, if it happened tomorrow, is predicted to reach 1.50 metres AHD. The 1949 flood is estimated to be a 1:20 year flood – more likely, but less serious than the 1:100 year flood.
Why has Council adopted sea level rise benchmarks of 0.4 metres by 2050 and 0.9 metres by 2100?
The NSW Government requires that, in determining appropriate sea level rise benchmarks, councils in NSW should consider information on historical and projected future sea level rise that is widely accepted by competent scientific opinion. Council receives its advice on projected sea level rise from pre-eminent scientific sources in Australia, such as the CSIRO, the Bureau of Meteorology, the NSW Chief Scientist and Engineer, and the NSW Office of Environment and Heritage. These organisations review scientific evidence about climate change including sea level projections.
The current rate of sea level rise off the coast of NSW is about 2.6 millimetres per year. The best available evidence is that mean sea level is expected to rise by 0.4 metres by 2050 and 0.9 metres by 2100. This means that sea level is expected to rise quicker in the future than it does now. Australian scientific bodies regularly review measured and projected rates of sea level rise, and they all advise that lower levels of sea level rise are highly unlikely. The next global review of measurements and projections is scheduled in 2021, and this will lead to a review of the Australian information.
How is the probability of a particular flood calculated?
There are various ways of expressing the flood probability, all meaning the same thing:
These all mean the same thing – on average, a flood of this magnitude is likely to occur once in every 100 years, or has a one per cent chance of occurring in any one year. In reality, a 1:100 year flood could occur twice in one year, but that is very unlikely.
A small increase in lake levels will occur more often than a large increase. For example, the estimated 20% AEP flood in Lake Macquarie will reach 0.82 metres AHD, the 5% AEP flood will reach 1.23 metres AHD, and the 1% AEP flood will reach 1.5 metres AHD.
These levels, and the probability of them occurring, are calculated by using models that can predict the likelihood of future events. The models are tested and calibrated against historic records of rainfall, tides, and floods.
The same measures of probability are used to describe other natural events – winds, storms, high tides, storm surges, and rainfall, for example. The more frequent the event, the less severe it is. A 1% AEP storm will be more severe than 20% storm.
What is the Lake Macquarie Waterway Flood Risk Management Study and Plan?
Lake Macquarie is a tidal lake in the Hunter Region of New South Wales, providing commercial and recreational use, as well as having high scenic value. The Lake has a permanently open outlet into the Pacific Ocean via the narrow and shallow Swansea Channel. It is one of the largest coastal lakes in eastern Australia with a foreshore more than 174km in length.
The Lake Macquarie Waterway Flood Risk Management Study and Plan, adopted by Council in June 2012, identifies properties near the Lake that are currently flood affected during a large flood event, and the additional properties that would be affected by flooding if permanent Lake levels rise 0.9 metres in the future. Approximately 7500 homes may be affected in a serious flood when lake levels rise by 0.9 metres. Scientific advice indicates such a rise is likely within the next 80-100 years.
Many low-lying properties already experience poor drainage, periodic flooding and occasional inundation during high tides, and these hazards would increase with gradually rising lake levels. The Lake Flood Risk Management Plan recommends Local Adaptation Plans be prepared for these low-lying areas.
What is the Coastal Zone Management Plan?
What is the Coastal Zone Management Plan?
Council’s Coastal Zone Management Plan (CZMP) 2015-2023 has been prepared in accordance with State Government legislation. The CZMP aims to preserve and enhance the environmental value of the coastline, estuary and channel amid increased visitation and pressure from urban development across the City. The CZMP has been prepared in collaboration with the NSW Office of Environment and Heritage, as well as other agency and community stakeholders.
Most actions are for Council to implement, but long-term environmental health and community wellbeing and enjoyment also require contributions from State agencies, particularly NSW Trade and Investment (Crown Lands Division), businesses and the community. The southern part of the Lake Macquarie catchment is located in Wyong Shire, so a healthy lake also depends on the actions of Central Coast Council.
Will I have to make any changes to my property because it is a flood hazard area?
Any development conditions, such as floor heights or set-backs, resulting from flood studies and risk management plans, only apply to new developments, so there is no need to make any changes to your existing property. However, if you decided to substantially re-develop your property or build a new development, you will have to meet the new conditions.
Is sea level rise included on a Section 10.7 Certificate?
A Section 10.7 Certificate (formerly 149) is a mandatory certificate you need to get when purchasing a property. It is a planning certificate under Section 10.7 of the Environmental Planning and Assessment Act 1979.
Planning certificates give information on the development potential of a parcel of land including the planning restrictions that apply to the land on the date the certificate is issued. There are three types of 10.7 planning certificates; 10.7 (2), 10.7 (2) Clause 3 Complying Development and 10.7 (2&5).
Most properties in low-lying parts of the City have had a flood risk notation on the Section 10.7 Certificate since 1997 (or before).
There has been no change in the number of properties with flood notations (which includes sea level rise) since 2012.
In 2012, the specific reference to sea level rise on Section 10.7 certificates was removed, as this potential future risk was incorporated into the reference of hazard from flooding.
What goes on my property certificate (Section 10.7 Certificate)?
Councils are required by law to indicate if any special development conditions apply to particular properties. They do this by placing a notification on the property certificate (Section 10.7 Certificate, formerly 149). This alerts owners, prospective buyers, or anyone else with an interest in a particular property that special conditions may apply.
Since mid-2009, all properties around the lake foreshore below three metres AHD have an indication on their Section 10.7 Certificate that they may be affected by special development conditions because of lake flooding. About two-thirds of the affected foreshore properties – those below two metres AHD - have had a flood condition on them since the 1990’s.
Are Section 10.7 certificates affecting property values?
The latest real estate information from the Estate Agents Cooperative database shows the capital growth of property values in Marks Point, Swansea, and other areas of the City, have increased. Marks Point has increased by 5.8 per cent, Swansea by 4.3 per cent, Eleebana by 8.7 per cent and Coal Point by 10 per cent. The average increase across the City was 4.3 per cent.
Changes in property values have been seen across the City due to factors such as the global financial crisis, housing supply, and interest rates, but these changes affect all types of property, not just those noted as flood-prone on Section 10.7 certificates (formerly 149).
If Council is looking at implementing flood control measures for possible sea level rise in 50 years’ time, then why should residents have it noted on Section 10.7 certificates now?
New roads, drains, and homes built today will still be around in 50 to 100 years, so we have to build them now to suit future conditions as well as today’s conditions.
Under NSW law, Councils have to provide information on any planning policies, hazards, or development controls that apply to a particular property. This includes things such as the land zoning, mine subsidence, State Environmental Planning Policies, and flood risk. This information is supplied on a Section 10.7 certificate (formerly 149).
Because properties in or adjoining flood-prone areas have special development conditions, such as a floor height requirement, this has to be shown on the Section 10.7 Certificate. The Lake Macquarie certificate simply answers the question “Whether or not development on that land or part of that land…is subject to flood related development controls”. For flood prone properties, the answer is “yes”. This applies to all foreshore properties less than 3 metres above the Australian height datum (AHD).
Most properties in Marks Point and Belmont South have had a flood notation similar to this on their Section 10.7 certificates since 1997, and many since the 1970’s.
Effective adaptation planning is timed, so that actions are implemented when they are required, to respond to increase in risk. This also allows for the best available science and technology to be used when it is needed.
What is Australian Height Datum (AHD)’?
‘AHD’ stands for ‘Australian Height Datum’. It is a standard Australia-wide reference point for measuring height. The zero point (0 metres AHD) is based on the Australian average sea level in 1966-68, so 1.0 metre AHD is approximately the same as 1.0 metre above average sea level.
What is freeboard and why is it added to flood planning levels?
'Freeboard' is a margin of safety applied on top of estimated flood levels to allow for factors such as wind waves, flood debris, the local effects of adjoining structures, changes in rainfall due to climate change, local topography, channel blockages and filling on the flood plain.
The standard allowance for freeboard is 0.5 metres. The NSW Flood Risk Management Guide says that allowance for projected sea level rise should be calculated separately and should not be included in freeboard. Floor levels for new buildings in flood prone areas are typically set at 0.5 metres above the 1:100 year flood level.