Stormwater Management

GWE specialises in managing the effects of stormwater runoff from urban areas and modified rural catchments to streams and rivers. Our solutions are aesthetically designed and meet regulatory standards for water quality and flow control.

An Integrated Approach to Stormwater Solutions

GWE’s approach to stormwater management incorporates the understanding of client and community needs, evaluating flood risk, the assessment of environmental sensitivities and the effects of stormwater discharges and developing sustainable environmental outcomes.

Stormwater – What We Do

We undertake the following Stormwater related work:

  • Flood impact assessment
  • Stormwater management plans
  • Stormwater networks design
  • Resource consent applications
  • Erosion and sediment control plans

Flood Impact Assessments

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, levels for land disposal of treated 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

GWE’s approach to stormwater management incorporates identifying client and community needs, evaluating flood and stormwater discharge effects on the environment and developing Water Sensitive Design (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 re-use
  • Detention tanks and ponds
  • Permeable paving, soak pits and infiltration
  • Wetlands
  • Sand filters, rain gardens and other stormwater filtration

Stormwater Networks Design

Our engineers have extensive experience with the hydraulic modelling and design of culverts, open channels and stormwater pipelines for greenfield and brownfield developments. Designs include detention basis and constructed wetlands to achieve stormwater neutrality, where post development effects are equal to or better than predevelopment 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 and Building Consent Applications

The stormwater discharge from most developments in Auckland 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 and Sediment Control

We work with our 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
  • Stabilising the soil
  • Removing sediment from water before it leaves the site