Southern inland floodplain management plan replacement project

  • February 22, 2023
  • Posted by: Madrigal Admin
  • Category: Tender News
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Tim Entwisle on site on the Macquairie river in about 1998 on a floodplain management plan project
A colleague of Tim Entwisle's on site on the Macquarie River in 1998.
A colleague of Tim Entwisle’s on site on the Macquarie River in 1998.

The NSW Department of Planning and Environment (DPE) is looking for companies to develop models for the Murray River, Murrumbidgee River, Lachlan River (multiple), and Billabong Creek valleys. The project is part of the southern inland floodplain management plan replacement project. Each of the valleys is being tendered separately.

The tender sets out the standard specifications for the hydraulic modelling services in great technical detail (really only for experts). The DPE requires that the modelling is consistent and of high quality.

Purpose of the floodplain management plan project

Tim Entwisle in 1998 on site at a weir on the Macquarie River for the Department of Water Resources.
Tim Entwisle in 1998 on site at a weir on the Macquarie River for the Department of Water Resources.

The purpose of the hydraulic modelling is to develop new floodplain management plans that meet the requirements of the Water Management Act 2000. These replace the old plans that were created under the Water Act 1912. The old plans were designed to benefit both rural communities and the floodplain environment.

The DPE will replace the 10 old plans with four new ones covering the valleys of the Lachlan River, Murrumbidgee River, Murray River, and Billabong Creek.

Specifications for the modelling

To make the southern inland floodplain management plan replacement project more manageable, each study area has been divided into several smaller work packages. The hydraulic models need to be set up so that they are consistent across all the work packages.

The supplier needs to use a specific modelling approach for creating the hydraulic models, called the 1D/2D TUFLOW HPC hydraulic model. This model setup has been chosen because it balances model accuracy and runtime, is easy to develop, and makes it simpler to process inundation extent. There are other technical specifications including:

  • sub-grid sampling (SGS) to use the same resolution as the input DEMs (digital elevation models) wherever possible
  • the model to be done in 2D, but some important structures, such as culverts, will be modelled in 1D
  • the quadtree method may also be used to improve the resolution of certain features like embankments, levees, channels, and other flow control areas.

Madrigal experience

Old style fishway on the Macquarie River
Old style fishway on the Macquarie River

The southern inland floodplain management plan replacement project is of great interest to Tim Entwisle, Principal at Madrigal. Tim was heavily involved in modelling projects in the 1990s at the Department of Water Resources (which is one of the ancestor organisations of DPE). The projects were statewide and he travelled extensively over the state on these projects including to Macquarie Marshes, Gwydir Wetlands, Lachlan Anabranch and Menindee Lakes. He was also the project manager for the NSW Water Reform Task Force that developed the technical and management framework on which the Water Management Act 2000 was based.

Contact us

The tenders close on 15-Mar-2023 11:45pm. Contact us if you need help putting together your tender for this exciting project.