Floodplain mapping – FAQs

Note: In the event of a flood emergency, the SES is the first point of contact– telephone 132 500. 

  1. What does ‘flood prone’ mean?
  2. How can I tell if my property is flood prone?
  3. What do the different colours on the maps mean?
  4. My property is within the flood prone area.  Does that mean my property will get flooded?
  5. How accurate are the maps?
  6. If my property is flood prone, will that have an impact on the value of my house or property?
  7. My property is within the flood prone area.  Will that mean I have to pay a premium for flood insurance?
  8. If my property is flood prone, will that have any implications for what I can do with my property – eg approval for new buildings or land uses?
  9. My property is within the flood prone area.  What is Council going to do to prevent my property from being flooded?
  10. My property is within the flood prone area.  How can I protect my family and property from flood risk or damage?
  11. My property is not in the flood prone area.  Does that mean I will not be flooded?
  12. I have owned this property for many years and it has never flooded here.  What has changed that has made my property flood prone now?
  13. Will the State Emergency Services (SES) be able to assist in the event of flooding?
  14. Where do I go for more information about the flood plain mapping?

Q: What does ‘flood prone’ mean?

A: The flood maps we have prepared show the estimated area and depth of flooding in the catchment in a 1:100 ARI and a range of other ARI flood events.  The 1:100 ARI flood is the generally adopted, national risk management standard for flood management, noting that a 1;100 ARI flood event is something that may not occur in a typical lifetime – it is a significant event! (We have not had even close to a 1:100 ARI flood in any catchment in our City in the last 50 years).

Detailed technical information on how we develop these maps, and what is meant by ARI can be found here.
Your property is considered to be “flood prone” or within a “flood management area”, if your property is within the flood extents (the coloured overlay) shown on the flood maps for a 1;100 ARI flood event.  This means there is some probability that surface flows of water may pass over part or all of your property during a flood event of this magnitude.

The degree to which this may occur can only be estimated, and may vary from very shallow, slow moving water entering part of your property, to, in some instances, deep, fast flows passing through the property.  By looking at the depth of water (as per the colour code shown on the map legend) you can get an indication of the degree of flooding that may affect your property.

If your property is within the flood extents shown in the 1:20 ARI flood map, then this means that there is a high probability that during a larger storm event (like the 1:100 ARI flood) , surface flows of water may pass over part or all of your property.  If your property is only shown as being within the flood extents on the 1:100 ARI flood map, then there is still a probability that surface flows of water may pass over part or all of your property in a flood of that magnitude.

Our Development Plan also has some policies within the ‘Hazards’ section for addressing development proposed in ‘“flood management areas” for properties that are identified as flood prone in the 1:100 ARI flood maps. These policies may change and additional policies added as amendments are made to the Development Plan. The policies may apply to a development application and may require additional consideration to any hazard impacts. In addition to this, you may not be able to apply for a ‘complying’ development if you property is identified in a flood management area in the development plan.

Q: How can I tell if my property is flood prone?

A: There are three ways you can find out if your property is flood prone: 

  1. Firstly, if your house is in the flood prone area identified in any of our recent flood mapping studies, you, as owner or occupier, should have received a letter from us advising of this.
  2. Secondly, you can locate your property on the flood maps provided on our website and if the property is partly or wholly within the coloured flood prone areas on the maps, then your property is considered to be flood prone.
  3. Finally, if you are still unsure if your property is flood prone, you can contact, Customer Services on 8384 0666 and speak with one of our friendly officers.


Flood mapping example Ward St

Example

In the example above, all the properties on Ward Street, Gray Street and most of the properties on Gawler Street are flood prone, while only the properties on the east (right hand side) of Saltfleet Street north the roundabout are flood prone, and several properties on the west side, south of the roundabout, are flood prone.  This is because the coloured overlay showing flood depth also covers all or part of these properties.

Even if only a small part of the property is covered by the coloured layer, we still consider the property to be flood prone.

Q: What do the different colours on the maps mean?

A: For all of our flood mapping a map legend is used to give a guide as to how deep flood waters may be in any location.

The different colours in the legend indicate the depth of water (in metres) that may be expected.

The colour schemes for the legends vary from study to study.  You should refer to the legend provided on the flood map for your area to identify the extent or depth of flooding expected in your area.

Three legend examples are shown below:

Flood mapping legend examples

Flood depth example:

In the flood mapping extract below, street and property boundaries are shown as a white outline.

By referring to the legend on the right, it can be seen that the flood depth on Ward Street varies from the 0.5m - 1m range (shown in mid blue) in the centre and south eastern end of Ward Street. 

The flood depth progressively gets shallower to the north west near the junction with Gawler Street, to 0.25-0.5m (shown in light green), 0.1 - 0.25m (shown in light brown), and finally 0-0.1m deep (shown in light blue) at the very edge of the flood prone area.  On the eastern side of Gray Street, the depth varies up through 1-1.5m (shown in purple) to 1.5m to 2.5m (shown dark green).

If you need any help reading the map or legend, please give our customer service team a call on 8384 0666.

Flood mapping example Ward St

 

Q: My property is within the flood prone area.  Does that mean my property will get flooded?

A: If your property is within the flood prone areas on the flood plain maps, it is possible that flooding may occur.  Whether floodwaters may enter your dwelling will depend on the depth of flood waters, and a number of other factors associated with the design and construction of your house.

We recommend that you take steps to reduce the risk of damage or harm to your property in the event of a flood. Some practical measures for reducing this risk are detailed in our information sheet

Further information about flood proofing your home may be available from the State Emergency Service at www.SES.gov.au  (see our information sheet for contact details). 

However, you should also read the limitations to understand the limitations of flood plain mapping. 

Q: How accurate are the maps?

A: The mapping is intended as a guide only for development and strategic planning purposes and general information.  There are limitations on the accuracy of the maps.  Find further information and to help understand the limitations of flood plain mapping, visit our limitations page.

It is not possible to model to a very high degree of accuracy how stormwater will behave as it runs over complex surfaces, or even the type of rain events which will occur, as no two events are ever the same and we cannot predict with any certainty what rainfall events will occur in the future. 

The modelling used to create these maps simulates what may happen in a significant rain event. The modelling cannot take into account unique characteristics of individual properties that can influence flows, including buildings, fences and gardens.  In the development of flood modelling software and flood maps, valued engineering judgements, based on monitoring and scientific experiments, have been made regarding how flows will behave in these circumstances.

Q: If my property is flood prone, will that have an impact on the value of my house or property?

A: There are many things that can influence the value of a property.  If a property is identified as being flood prone, then the degree to which the property is flood prone may have an impact on the property valuation. This is because:

  1. The Development Plan may ask for additional criteria to be addressed when a development proposal is lodged for your property in the interests of reducing the risk of flood waters damaging buildings, and
  2. Potential purchasers may perceive this risk differently to you.

Q: My property is within the flood prone area.  Will that mean I have to pay a premium for flood insurance?

A: Following the severe flooding in the eastern states in 2011, 2012, the insurance industry and Australian Government have been working on making changes to the cover provided for flooding, with the intent of keeping flood insurance “affordable” and also making new rules on what is a flood and what isn’t, and what is covered by insurance and what is not. 

These discussions were still in progress (as at June 2013)

We suggest that if your property is within a flood prone area, you talk to your insurer(s) to ensure that you have appropriate cover for your property.

Q:If my property is flood prone, will that have any implications for what I can do with my property – eg approval for new buildings or land uses?

A: Our Development Plan has provisions relating to flood management areas.  The provisions vary to some degree depending on the form of development proposed.

You should discuss your intentions with our duty planning officer to see what provisions may apply.

Q: My property is within the flood prone area.  What is Council going to do to prevent my property from being flooded?

A: Council performs a statutory function under the Local Government Act to take measures to protect its residents from “hazards”, including flooding.  Floods in watercourses are a “natural” event and we cannot stop floods from occurring.  However our service level has been established to minimise the potential for loss and damage due to flooding, through a combination of good development planning, and effective flood protection infrastructure.

Our capital works program provides for funding for stormwater management works including flood protection, subject to Council’s overall budget restraints and priorities. 

Wherever it is feasible to improve local levels of flood protection, we will strive to achieve this in accordance with the resources available.  We design and construct our flood protection infrastructure to provide flood protection for all but the most extreme events.

However, flood protection may not be possible in all instances, or in the short term and that is why we are providing information to residents, and supporting the SES in running the “Floodsafe” and “Stormsafe“ programs across the city, so that you are informed of the things that you can do to limit loss, in the event that a flood does occur.

Q: My property is within the flood prone area.  How can I protect my family and property from flood risk or damage?

A: There are a number of things that property owners can, and should do to reduce the risk of damage or harm from flooding.
We have developed an information sheet with some suggestions. 

The SES has additional information available either by contacting them on telephone 8463 4171, or visiting their Floodsafe web page.

Additionally, the SES, in conjunction with council, will be running a program of Floodsafe community information sessions in your area, to help raise awareness, and help you to reduce the risk of damage or harm in the event of a flood.

Q: My property is not in the flood prone area.  Does that mean I will not be flooded?

A: Our flood mapping only simulates floods on the larger watercourses in our Council area.  It is impossible to simulate every possible form of storm event that may occur.  If your property is not within a flood prone area, there is statistically a lower chance of flooding occurring from a major flood event in the catchment.

However, even if your property is not within the flood prone areas identified by our flood mapping, due to the highly variable nature of our weather patterns, there is still some possibility that heavy rain may fall, creating local ‘flash flood’ conditions. 

By following the suggestions provided in our information sheet or through the SES “Floodsafe” and “Stormsafe” programs, you can help minimise the risk of harm or damage in the event of flash flooding.

Q: I have owned this property for many years and it has never flooded here.  What has changed that has made my property flood prone now?

A: In some areas, urban development has resulted in the potential for more stormwater to run off the land than would have been the case before European settlement, and this has been considered in developing the flood maps.

We do know there have been very significant rain and flood events in the past, before European settlement, which have helped shape the form of the area. 

However, compared to the length of time that the world’s climate has been reasonably stable (since the Ice Age many thousands of years ago), we do not have a very long record of rainfall or flooding in our area. 

Based on our statistical analysis and assessment of the relatively short rainfall history we have, there have been very few major events in the area since European settlement. There is a possibility that these major events can still occur, even though we have not seen one since early European settlement.

Our flood mapping provides a scientifically robust estimate of the probability of flooding from major events, but it cannot predict a specific event outcome. 

You should read our Limitations for more information.

Q: Will the State Emergency Services (SES) be able to assist in the event of flooding?

A: We have provided our flood mapping to the SES. Their emergency response will take account of this information to ensure that they can deliver the emergency response required in the event of flooding.

The SES is the first point of contact in the event of a flood emergency – telephone 132 500.

Q: Where do I go for more information about the flood plain mapping?

A: If you require more information about the flood plain mapping, please contact our Customer Service team on 8384 0666.

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