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Commercial Building image
2011

Waitangi Museum

Location: Waitangi, Bay of Islands, Far North District

Client: Waitangi National Trust
Salvation Army Auditorium Building
2020

Salvation Army Auditorium Building

Location: Aubrey Street, Whangarei

Client: The Salvation Army
Services

Stormwater Management

Efficient Stormwater Solutions

Northland’s intense rainfall makes stormwater one of the most important — and most scrutinised — parts of any development. Get it right and your site drains safely without flooding neighbours or waterways; get it wrong and it’s a consent risk and a long-term liability. RS Eng designs stormwater systems for everything from single dwellings to subdivisions and commercial sites: conveyance and drainage, on-site detention and attenuation to control peak flows, treatment to protect receiving environments, and disposal to ground where soakage allows. We design to council and regional standards and prepare the documentation to prove it.

Stormwater Management Services: 

We develop stormwater solutions tailored to each site, balancing performance, compliance and environmental protection.

Let's work together

Stormwater drainage design

Flood risk assessments

Detention and retention systems

Green infrastructure solutions

Regulatory compliance

When Do You Need Stormwater Management?

Stormwater design is required or strongly recommended in the following situations:

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  • Building a new home or structure
    Most new builds need stormwater design to manage roof and hardstand runoff. On larger or low-lying sites, or where you’re adding significant impervious area, councils require a more detailed design and often approval.
  • Subdividing or developing land
    Subdivisions and developments must manage the additional runoff they create — usually with detention or attenuation so peak flows don’t increase downstream. This is a core part of the engineering for resource consent.
  • Building on a low-lying or flood-prone site
    Where flood risk is present, stormwater design keeps buildings and access safe in large rainfall events. A flood assessment is often required before council will grant consent.
  • Discharging stormwater to water, ground or a network
    Discharges can trigger resource consent depending on scale and the relevant council rules. We assess the requirement and prepare the application.

What Makes Northland Stormwater Conditions Different?

Northland’s climate and ground make stormwater design more demanding here. Knowing the local conditions is why our systems perform in real storms.

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  • High-intensity rainfall and ex-tropical storms mean systems must be sized for severe, short-duration events.
  • Low-lying and flat coastal land drains slowly and floods easily, and outfall levels can be affected by tides — so conveyance and disposal need careful design.
  • Variable soakage is a defining local issue. Clay soils across much of Northland soak poorly, so disposal-to-ground solutions that work in sandy areas often won’t — soakage testing can be undertaken.
  • Sensitive receiving environments — estuaries, harbours and the coast — mean treatment to remove contaminants before discharge is increasingly required by Northland Regional Council. An RS Eng stormwater design is sized for your site’s rainfall, ground and outfall.
How the Process Works

We follow a clear process to assess the site, design the stormwater system, and deliver documentation ready for consent and construction.

Request a Consultation

  • Step 1 — Get in touch
    Tell us your site address and project. We’ll advise on the stormwater design required and provide a fee estimate.
  • Step 2 — Site assessment
    We review levels, catchment, soakage potential and flood risk — carrying out or coordinating soakage testing where disposal to ground is proposed.
  • Step 3 — Design and analysis
    We size and design the drainage, detention/attenuation, treatment and disposal, modelling peak flows so the system meets council requirements.
  • Step 4 — Consent documentation and sign-off
    We prepare the stormwater design and reports for consent and, during construction, provide the monitoring and sign-offs required. We’ll confirm timeframes when we scope the work.

FAQs

Attenuation and detention systems temporarily hold rainwater on your site — in tanks, ponds or underground storage — and release it slowly, so your development doesn’t increase peak flows and flooding downstream. Councils often require this for new builds and subdivisions.

Most new builds need at least basic stormwater design to manage roof and hardstand runoff. On larger or low-lying sites, or where you’re adding significant impervious area, a more detailed design and council approval are usually required.

Yes. We assess flood risk using council flood mapping and site-specific analysis, and design stormwater systems that keep buildings and access safe in large rainfall events.

On sites without a public connection we design on-site solutions — soakage/disposal to ground where the soil allows, or detention and controlled discharge — based on soakage testing and the site conditions.

Sometimes. Discharges to water, to ground or to a public network can trigger resource consent, depending on scale and the relevant council rules. We’ll advise whether consent is needed and prepare the application.