Back Stormwater - When rainfall tips the balance

Date: 21 December 2022

Upgrading Stormwater.

Weather in Auckland has been a hot topic lately. We discuss why upgrading stormwater may be required and why we have such issues in Auckland with stormwater; what problems can arise when stormwater fails, what consideration need to be made in regards to storm water if you are building or developing a site in Auckland and what can be done to minimise the risks – plus how we can help if you need to upgrade your stormwater!

Issues arising from heavy rain

Auckland seems to be becoming the new Suva with the ongoing muggy weather and tropical downpours of early summer. Let’s hope the rainy days don’t carry on into the remainder 2023.

Unfortunately, the intense downpours can be catastrophic, wreaking havoc with flooding and slips. This excess of water creates unsavoury problems in some central suburbs like Grey Lynn where they can contribute to an overflow of the sewerage system. This overflow can prevent people from swimming safely at many of our harbour beaches – which is especially a shame during the summer months!

How and why does stormwater cause issues in Auckland?

While stormwater (rain off roofs and other infrastructure) is generally designed to be separated from wastewater (the ‘grey’ water from toilets, laundries and kitchens etc.) some of our older suburbs unfortunately still see them mixed together in shared drains.

Combined sewers in Auckland can overflow into Meola Stream (Westmere), Remuera Stream, Newmarket Stream and Oakley Creek – one of Auckland’s longest urban streams flowing from Hillsborough through Mt Roskill and Waterview to the Waitemata Harbour.

Where such waterways run through private property the Auckland Council will maintain the waterway because of the concern for wider public safety including the risk of culverts blocking due to eroding stream banks.

Site development and stormwater

However new building work, from residential renovations to large scale commercial jobs, could benefit from the installation of retention tanks which Topline can customise to meet the specific site needs. Read more about commercial drainage > and residential drainage >

Storm water upgrades in Auckland

If you are considering building developments storm water systems need to be prepared to mitigate against potential flooding and related risks to property like site and structure stability, along with environmental considerations.

When planning a development, the Auckland Council may be able to authorise the discharge of stormwater under the region wide network discharge consent which sets out a range of requirements for connection to the stormwater network

Problems arising from stormwater issues

In urban environments, stormwater can create three major issues:

  • flooding, due to the volume of water
  • stream erosion, due to the increased speed of the water
  • water pollution, due to potential contaminants the water is carrying

Resource consent for stormwater

You may need to get a resource consent for stormwater matters, such as:

  • the size of impervious area on your site
  • where the stormwater is being directed to (potentially including a retention tank)
  • if the stormwater is coming from a high contaminant generating car park or a high use road
  • if your site is in a Stormwater Management Area.

Stormwater and pre-purchase considerations

Before buying a property, you should find out if there is a watercourse on the property which you may mainly be responsible for maintaining where it runs in and out of the property boundary.

Stormwater – how to minimise the risk of things going wrong

Generally, aim to keep your waterways free of litter, garden waste and fallen trees.

Do not use detergents, fertilisers or pesticides in areas where they might flow into the waterway.

Stormwater upgrades

If you need help improving your drainage for commercial stormwater or residential stormwater get in touch. We can also help with commercial retention tanks and residential rainwater solutions. Contact the plumbing, gasfitting and drainage experts, Topline, today by enquiring online or calling 0800 111 818.

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