Flooding FAQs

We have flood information for many areas across the LGA. This includes information about past and / or anticipated flood levels, and flood risk precincts.

There are two main ways you can get information from us about how flooding affects your property:

1. Apply for a Flood Certificate through the Flood Level Information request form
2. Apply for a Planning Certificate. You'll need to request a combined 10.7(2) and 10.7(5) planning certificate to get information about whether the property is flood affected, the 1% AEP (100 year ARI) flood level and flood planning level.

All properties within the Flood Planning Area have flood information available.

To view the Flood Planning Area, please visit our Online Mapping Tool.  We do not have flood level information for all properties, so if your property is outside of the Flood Planning Area you should call us on (02) 6648 4000 to check if information is available before you start an application.

For further general information about flooding and guides on how to stay safe and what to do in case of flooding, go to the NSW State Emergency Service website.

The Flood Certificate will provide the applicant with as much flood information as possible on the property in question. This form may be useful if you are looking to develop a property, or are considering purchasing within the floodplain. The form provides additional flooding information that otherwise would not be captured within a 10.7 (Parts 2 and 5) Planning Certificate.

If flood information is available for your property, we aim to provide the following:

• Flood Risk Precinct (if available)
• Approximate ground level information
• Floor Level data (if available)
• Planning Levels (Design Flood Level, Flood Planning Level)
• Estimated flood levels for a range of events (20% AEP, 1% AEP, PMF, etc)
• Climate change flood levels (if available)
• Historical flood levels in close proximity to the address (if applicable)
• The associated Flood Hazard and Categorisation (if available)

The flood information we are able provide in this certificate will vary between catchments, and not all of the information may be available for all properties.

Some large and rare floods have often not been experienced since European settlement commenced, computer models are used to simulate the depths and velocities of major floods. These computer models are normally established and operated by flooding experts employed by local and state government authorities.

Because of the critical importance of the flood level estimates produced by the models, such modelling is subjected to very close scrutiny before flood information is formally adopted by a council.

Maps of flood risks (e.g. 'low', 'medium' and 'high') are prepared after consideration of such issues as;

• flood levels and velocities for a range of possible floods;
• ground levels; flood warning time and duration of flooding;
• suitability of evacuation and access routes; and
• emergency management during major floods

Flood risk maps are currently not available on council’s online mapping tool, however flood risk information is presented in the flood certificate provided as part of a Flood Level Information Request.

As part of the floodplain risk management process, flood studies and flood risk management plans are reviewed over time. As these reviews take place, computer models are revised and predicted flood levels and associated flood mapping can change. The resultant change in flood levels and flood mapping however is normally very small. These changes are not expected to occur very often and the intervals between revisions to the maps would normally be many years.

The reasons why the computer models are revised can include;

• new rainfall or ground topography information becomes available;
• new floods occur which provide additional data from which to fine-tune the models;
• better computer models become available as the science of flood modelling improves and computer capabilities increase;
• flood mitigation works may have been carried out,
• development within the catchment may have occurred, that was not previously simulated in the models.

Any change in a council's classification of properties can have some impact on property values. Nevertheless, councils normally give due consideration to such impacts before introducing a system of flood risk classifications or any other classification system (e.g. bushfire risks, acid sulphate soil risk, etc).

If your property is suddenly classified as being in Flood Prone the real flood risks on your property have not changed, rather, present information regarding risk estimates has become more available for Council to inform decision making. A prospective purchaser of your property could have previously discovered this risk if they had made enquiries themselves.

Ultimately, the market determines the value of any residential property. Individual owners should seek their own valuation advice if they are concerned that the flood risk estimation may influence their property value.

Yes, you should confirm the specific details of your current insurance situation about flooding directly with your insurer. Individual insurers decide what criteria they use to determine flood risk and insurance premiums use data from multiple sources.

f you have experienced significant insurance premium increases, there are two main avenues to pursue to find lower premium cover:

• Shop around and get quotes from a range of insurance companies, as they all calculate flood risk in slightly different ways.
• Compare the updated flood information (mapping) for the 1% AEP for your property. Is your house footprint outside the flood extent (not shown as flooded)? Is the internal floor level for habitable rooms higher than the ground level of your property, raising it above the identified depth of flooding in a 1% AEP event? Take this information to your provider and have a discussion with them.

Further information on flood insurance(PDF, 838KB)

A 1% Annual Exeedance Probability Flood, also known 100 year ARI flood, means you have a 1 in 100 chance that a flood of that size or larger could occur in any one year. It does not mean that if it floods one year, it will not flood again for the next 99 years.

The 100 year flood terminology is misleading, hence the preference for using the 1%  AEP or 1 in 100 annual chance flood.

Some parts of Australia have received a couple of 100-year floods in one decade. The probability of experiencing a 1% AEP flood in a particular location over an 80 year period is about 55%, and the chance of experiencing two is around 19%.

The 1% AEP flood level is generally used as the Design  Flood Level for most types of development. The extent is the area below this level that will be impacted by a flood of this magnitude.

The probable maximum flood (PMF) is the largest flood that could possibly occur. It is a very rare and improbable flood. Despite this, a number of historical floods in Australia have approached the magnitude of a PMF.

Every property potentially inundated by a PMF will have some flood risk, even if it is very small. Under the State Government changes implemented during 2001, councils must now consider all flood risks, even these potentially small ones, when managing floodplains. As part of the State Government changes, the definitions of the terms 'flood liable', flood prone' and 'floodplain' have been changed to refer to land inundated by the PMF.

The Flood Planning Level is a height used to set floor levels for property development in flood prone areas. For the majority of development it is defined as the level of a 100-year flood (1% Annual Exceedance Probability) plus 0.5 metres freeboard. This level may be higher for vulnerable land uses (e.g. hospitals or schools).

The flood planning area is the area below the Flood Planning Level and as such subject to flood related development controls.

Land affected by the Indicative Flood Area/Indicative Flood Planning area have been determined through preliminary flood modelling and does not truly represent the 1% AEP (1 in 100 year) flood extent, however Council is confident these areas are flood affected. The Indicative flooding extent is primarily designed to identity flood prone land in areas that do not have detailed flood studies.  

Properties within the Indicative Flood Area/Indicative Flood Planning Area are subject to flood related development controls. If development or rezoning is proposed, then further detailed flood assessments may be required. 

Freeboard is a factor of safety expressed as the height above the design flood level to compensate for uncertainties in the estimation of flood levels across the floodplain, such as wave action, localised hydraulic behaviour, unforeseen blockages and impacts that are specific event related, including levee and embankment settlement, and other effects such as climate change. Freeboard is usually 0.5m above the design flood level.

AHD refers to Australian Height Datum, a common national plane of level approximately equivalent to the height above sea level. All flood levels, floor levels and ground levels in Council studies have been provided in metres AHD.

The chance of a flood of a given or larger size occurring in any one year, usually expressed as a percentage. E.g. if a peak flood discharge of 800 m3/s has an Annual Exceedance Probability of 1% it means that there is a 1% chance (that is a one-in-100 chance) of a 800m3/s or larger events occurring in any one year.

A holding pond created by regrading an area or construction a levee that temporarily detains stormwater or flood run-off during big storms. They are designed to offset the impacts of urban development and/or reduce impacts of flooding. The basin can be ‘dry’ (does not permanently hold water) or ‘wet’ (permanently hold water). Dry basins retain water only during storm events, later releasing the water at a controlled rate until the basin empties. Hence the basin remains dry between rain events.

It is the property owner's responsibility to ensure stormwater overflow from development works, buildings and paved areas is collected, mitigated and/or directed to the street.

If you have concerns about stormwater issues please contact council on 02 6648 4000.

Generally if it is a recent subdivision, councils Subdivision Engineer will investigate. If it is coming off defective guttering or being directed by pipes or similar (for example a concrete path) onto your property our Building Compliance Team will investigate.

If you have concerns about a natural waterway or stormwater drain please contact our Council on 02 6648 4000.

Clearing creeks will enable more water to flow but will not prevent flooding during rare floods and will potentially increase flooding impacts downstream. Creeks can only take so much water before they overflow regardless of any debris or vegetation. During rare floods, the whole of the floodplain is activated and more water flows on the floodplain than in the creek or river.

If your question about flooding/flood risks in the Coffs Harbour LGA isn't answered on our flooding webpage or by our online mapping, you can obtain more detailed information such as flood levels for a specific property by submitting a Flood Level Request Form with the appropriate fees.

For further general information about flooding and guides on how to stay safe and what to do in case of flooding, go to the NSW State Emergency Service website.