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Flooding- is your site affected?

We are all becoming more aware and cautious of flooding risks when looking at potential properties to develop, buy for ourselves or to rent.


Following the January and February 2023 flooding events in Auckland, Auckland Council has recently updated its flood modelling and published updated flood maps. This will make it easier for people to identify areas that are more at risk to flooding, based on the updated information and flood modelling.


The 1 per cent annual exceedance (AEP) floodplains indicated on Auckland Council Geomaps have a 1% chance of occurring or being exceeded in a year. The updating flood modelling may show previous floodplains that have now extended or areas that are now subject to flooding where it wasn’t identified before.


How can you access the updated flooding maps?

The updated flooding maps can be found via both Auckland Council’s Geomaps here and its new Flood Viewer here. These maps show the 1% AEP flood event, and also “flood prone areas”. The Flood Viewer is more accessible as it supports users on all devices, whereas Geomaps is only available on desktop.


How to access the flooding data on Geomaps

  • To view the maps, you first need to go into Auckland Council’s GIS Viewer, Geomaps, here.

  • After this, enter your property address.

Image source: Auckland Council GIS

  • You can then turn on the ‘Natural hazards’ layer by ticking this option, and select ‘Flood Plains’ from the legend. This will show whether your property is subject to the 1 in 100 year flood plain. This is the flood plain that rules in the Auckland Unitary Plan relate to, and which could trigger the need for resource consent.


Site specific investigations

If your site is within the 1% AEP floodplain and you are wanting to undertake development on the site, you should discuss your project with an engineer early in the process. Your engineer will undertake site specific investigations in relation to flooding and prepare a flood risk assessment that assesses the extent of the flooding on your specific site.


The floodplain shown on Auckland Council’s Geomaps can be different to the flooding risks identified by your engineer as the Council’s updated flood modelling uses a conservative approach and is also a high-level model (rather than related to site specific investigations). Once your engineer has confirmed the extent of the floodplain in relation to your site and provided assessment of it, you can then understand the potential risks associated with your development, how you can avoid these effects, or mitigate them.


When will I need a resource consent?

If you want to build (such as a new dwelling, or additions to a dwelling) or locate structures within a floodplain, resource consent will often be required under the Auckland Unitary Plan. Resource consent is also required for the use of new buildings or the change of use of existing buildings to accommodate “more vulnerable activities”, including activities such as dwellings and boarding houses.


There are also restrictions related to the earthworks within floodplains associated with your development that you need to be aware of, such as earthworks to establish the building platform of a building within a floodplain. The Auckland Unitary Plan requires that earthworks within the floodplain not raise ground levels more than 300mm, to a total fill volume up to 10m3. If this is exceeded, resource consent will also be required. This relates to changing flood volumes in the flood plain.


The flooding risk assessment undertaken by your engineer should be submitted as part of your resource consent application, outlining how flooding risks will be avoided or can be managed.


Need help with your development?

If you want to undertake development on your site and are unsure how it may be impacted by floods, get in contact with our team of experienced, qualified planners. We can identify resource consent requirements, how to minimise consenting risk and assist with the resource consent application.


We also work with a wide range of specialists, including engineers, to make sure you get the best team for you and your project.


You can contact us on hello@planningplus.co.nz or (09) 427 9966.



Mary Zhou is a Planner at Planning Plus®. Mary has been part of the Planning Plus team since 2021 and has a real passion and drive for all things planning. Mary has experience with a variety of projects including rural and urban land use, subdivision and feasibility analysis.





Disclaimer

Please remember that the advice in this blog is general in nature and based on information and advice available at the time of writing. We recommend you get your own planning advice. As with all our blogs this information is preliminary in nature only and we have used our best endeavours to ensure it is correct at the time of writing. It is not intended to substitute for your own investigations or obtaining specific advice from professionals. Planning Plus LtdTM is not liable in any way for any errors or omissions.

© Planning Plus Ltd 2023


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