Serpentine catchment drainage planning

The Serpentine catchment drainage planning area is a highly constrained area that contains high groundwater levels, multiple Water Corporation owned main drains and is prone to flooding and inundation.

This area is increasingly being considered for urban development, with the Western Australian Planning Commission identifying areas for future development in the subregional frameworks. To enable this future development, it is important that the high-risk water constraints are considered and managed as part of the land planning and development in this area.

Catchment area

The Serpentine catchment drainage planning area is located on the Swan Coastal Plain and is bounded by the Darling Scarp in the east, the Indian Ocean to the west, the Jandakot Mound in the north and Dirk Brook in the south. The terrain is characterised by gently undulating dunal systems near the coast, several wetland systems that are associated with inter-dunal depressions, and an extensive open drainage network.

This network includes the Water Corporation owned Birrega, Oaklands, Peel and Punrak Main Drains, associated branch drains, and the lower Serpentine River, which eventually discharges to the Peel-Harvey estuary to the south of the plan area.

We have prepared guidance and advice on the management of water for future development in the Serpentine catchment below.

Drainage and water management plans

As part of catchment drainage planning, we provide our stakeholders with an understanding of the movement of stormwater (flooding) and groundwater water in the landscape and its interaction with other features such as wetlands, rivers and existing drains in the context of future development.

This information is presented in the form of a drainage and water management plan (DWMP), which provides approaches to enable development while also protecting infrastructure and human safety and life.

The Lower Serpentine area has been identified by the Western Australian Planning Commission and local governments for future urban growth. We have initiated drainage planning in the area and have produced drainage and water management plans and related technical studies for several catchments.

Birrega and Oaklands including East of Kwinana drainage and water management plan

The Birrega and Oaklands and East of Kwinana drainage and water management plan (including the East of Kwinana planning investigation area) is in preparation. We have prepared technical studies to guide the development of the plan in this area.

Byford drainage and water management plan

The Byford drainage and water management plan provides guidance on water management issues for the Byford Townsite area, in the local government area of Serpentine and Jarrahdale.

Jandakot drainage and water management plan

The Jandakot drainage and water management plan provides a guide for developers and stakeholders to enable development to proceed, particularly regarding stormwater management issues. It supports the Jandakot structure plan and relates to the Peel main drain catchment.

Supporting technical studies

We prepare technical studies to provide an understanding of the movement of stormwater and groundwater in the catchment and to consider flood and inundation risks, and prepare flood mapping to influence better water and land use planning. These studies provide the technical basis for the drainage water management plans and will facilitate development in this highly challenging area.

A series of hydrological studies were completed to understand the distribution and movement of surface water and groundwater in the landscape. In particular, how the surface water interacts with the high groundwater in the area. These studies provide the technical information for the DWMPs in the area.

The advantage of this approach is that the studies use scenarios to project and determine the effects on the hydrological regime of the area for pre- and post-development conditions.

The hydrological studies are presented in three separate reports:

the Lower Serpentine hydrological studies - Conceptual model report, which characterises the hydrology and hydrogeology of the area
the Lower Serpentine hydrological studies - Model construction and calibration report, which describes the construction of the MikeSHE numerical model based on the conceptual model
the Lower Serpentine hydrological studies - Land development, drainage and climate scenario report, which analyses and discusses scenario results in the context of hydrological constraints.

The flood modelling and drainage studies are developed at a catchment scale. The objective of these studies is to understand the flood behaviour under the existing catchment conditions before development and then assess the risks and benefits of different future development scenarios through flood mapping.

A hydrologic and hydraulic assessment is conducted for the designated catchment area.

A hydrologic assessment or model assesses the runoff of surrounding and upstream catchments into the catchment of interest. The hydraulic flood model is used to simulate flood behaviour, map flood extent and determine water level and discharge at various locations.

Most major rural drains in the area are managed by the Water Corporation. Our department and the Water Corporation have dual responsibility for managing drainage and flooding in this area.

The flood modelling and drainage studies:

The East of Kwinana flood modelling and drainage study defines the nature and extent of flooding in the Birrega and Oaklands catchments with the outlet being the Serpentine River and eventually the Peel-Harvey estuary. It supports the Birrega and Oaklands DWMP. This document is available on request. The previous studies are the Birrega and Oaklands flood modelling and drainage study and the North-East Baldivis flood modelling and drainage study.
The Punrak flood modelling and drainage study covers both Punrak and Dirk Brook catchments and was undertaken to define the nature and extent of flooding for any future development in the area. This document is available on request.

The East of Kwinana and Ravenswood and Pinjarra planning investigation area flood risk management and land capability assessment takes a floodplain risk management approach to analyse and provide advice on flooding in the East of Kwinana and Pinjarra-Ravenswood areas as identified in the Perth to Peel 3.5 million sub-regional frameworks.

The report is a technical engineering analysis that supports the Birrega and Oaklands (including East of Kwinana) DWMP.

Floodplain risk management and land capability advice was provided to Western Australian Planning Commission to assist in the determination of the land uses in the area. The report and determination are available on the Department of Planning, Lands and Heritage website. This document is available on request.