Why GWE for Stormwater
Protect against flooding and erosion
evidence-based modelling to protect communities and infrastructure.
Healthy waterways & protect the environment
smart stormwater design that treats contaminants and balances development with nature.
Regulatory certainty
clear, defensible modelling and reporting that satisfy councils and consents.
Sustainable development
practical engineering meets Water Sensitive Design to create lasting solutions that stand the test of time.
What we do
Flood Impact Assessment & Hydrologic / Hydraulic Modelling
Flooding is a common hazard for many developments in urban and rural environments and is based on numerous factors including site topography, rainfall intensity and soil conditions. GWE undertakes hydrologic and hydraulic modelling for sites that are prone to flooding. We identify the extent of flooding and overland flow paths and advise our clients on how to develop sites by advising on floor levels for structures, land disposal solutions for treated stormwater and/or wastewater and provide solutions to maximise usage of land. We use techniques such as:
LiDAR surveys
GIS tools
Rapid flood hard assessments
TUFLOW, InfoWorks ICM
Stormwater Management Plans (SMPs) & Water Sensitive Design (WSD)
GWE’s approach to stormwater management incorporates identifying client and community needs, evaluating flood and stormwater discharge effects on the environment and developing WSD solutions to manage those effects. Site specific, sustainable outcomes are achieved through a balanced use of conventional stormwater infrastructure, WSD devices and enhanced natural systems with emphasis on:
Rainwater tanks and stormwater reuse (stormwater retention)
Detention tanks and ponds
Permeable paving, soak pits and infiltration
Wetlands
Sand filters, rain gardens and other stormwater filtration (stormwater quality treatment.
Stormwater Network Design
Our engineers have extensive experience with the hydraulic modelling and design of culverts, open channels and stormwater pipelines for greenfield and brownfield developments. On-site Stormwater Designs include detention basins and constructed wetlands to achieve stormwater neutrality, where post development effects are equal to or better than pre-development effects. This is achieved through best practice modelling and design tools such as:
HEC-HMS and HEC-RAS
TUFLOW, InfoWorks ICM
CulvertMaster and FlowMaster
Specialist in-house programmes
Resource & Building Consent Applications & Regulatory Support
In Auckland, the stormwater discharge from most developments will be covered by a regional network discharge consent held by the council. However, the management of stormwater within a development will have to follow the rules of the Unitary Plan and this will have to be demonstrated through a stormwater management report that will accompany a building consent application.
GWE provides advice on the consenting requirements and will produce technical and planning reports to support applications for a building consent. The consent application will need to demonstrate:
A statutory assessment of the development has been completed
Appropriate design considerations have been made to manage stormwater
Compliance with the activity standards for the development
Erosion & Sediment Control Plans
We work with civil engineers to undertake earthworks design and use a range of techniques to prevent sediment entering natural waterways. We develop erosion and sediment control plans to meet local Council standards by:
Managing the quantity of water entering the site
Controlling how water flows through a site (diversion bunds)
Stabilising the soil
Removing sediment from water before it leaves the site (Sediment Retention Ponds SRP’s, and/or Decanting Earth Bunds DEB’s)
Water Reticulation
We assist clients with the design of water networks and pressure boosting pump stations, delivering systems that can be handed over to Council for long term management or operated privately by industry or body corporates. Our expertise covers:
Network modelling
Reticulation layout and design
Hydraulic, mechanical & civil design
Materials selection
Water hammer analysis
Reservoir siting and design
Pressure boosting stations
Sewage Reticulation
We assist clients with the design of wastewater pipelines and pump stations, delivering systems that can be transferred to Council for long-term management or operated privately by industry or body corporates. Our expertise covers:
Network modelling
Reticulation layout and design
Hydraulic, mechanical & civil design
Materials selection
Water hammer analysis
Low pressure and vacuum collection systems
Pumping stations
Why Choose GWE
Expert stormwater design
our water engineers produce site‑specific SMPs and robust hydrologic/hydraulic modelling.
Sustainable by design
we integrate Water Sensitive Design and nature‑based solutions to improve quality and reduce loads.
Compliance, made clear
consent‑ready documentation aligned with Unitary/Regional Plan rules and council technical guidance.
Risk managed end‑to‑end
How we work (LIFT)
L
Listen
we begin by mapping catchments, assessing existing flow paths, site constraints and regulatory expectations.
I
Innovate
we use modern stormwater modelling and Water Supply Design, creating compliant solutions that ease infrastructure demand and enhance environmental outcomes whilst delivering resilient results.
F
Follow Through
accountable at every stage, we deliver reports, manage consents, oversee construction and validate results.
T
Team Up
we coordinate planners, ecologists, engineers and contractors so stormwater solutions integrate smoothly with all parts of your development.
Frequently Asked Questions.
What is a Stormwater Management Plan (SMP)?
An SMP summarises how stormwater is managed on your site: run-off modelling, device selection, flow control and quality treatment, with rationale and mitigation.
Do I need to get a stormwater discharge consent?
Often yes. Even where regional network consents exist, your development must comply with the Unitary Plan rules and provide evidence via reports.
What tools and models do you use?
We employ industry-standard models (e.g. TUFLOW, InfoWorks ICM) and GIS/LiDAR data to deliver robust flood and flow analysis.
Can I use natural or green infrastructure instead of big pipes?
Yes, we specialise in Water Sensitive Design (WSD), integrating ponds, swales, permeable surfaces, infiltration and wetlands to reduce the reliance on traditional systems.
How long does the stormwater design and consent process take?
It varies by complexity, but planning, modelling, design and consenting often span several months, particularly for larger developments.