The Department of Water and Environmental Regulation produces floodplain mapping of rivers and major watercourses and provides floodplain development advice to ensure that proposed floodplain development has adequate flood protection and does not impact on the existing flood regime of the area.
This advice is related to major river flooding only. Other issues, such as stormwater drainage and envirionmental and ecological considerations are not addressed.
This dataset contains 20 extent types as follows:
Extent of 1 in 10 (10%) AEP flooding
Extent of 1 in 20 (5%) AEP flooding
Extent of 1 in 25 (4%) AEP flooding
Extent of 1 in 50 (2%) AEP flooding
Extent of 1 in 100 (1%) AEP flooding
Extent of flooding - Designated flood event
Extent of 1 in 200 (0.5%) AEP flooding
Extent of 1 in 500 (0.2%) AEP flooding
Extent of maximum channel capacity
Extent of probable maximum flooding
Extent of study - 1 in 10 (10%) AEP
Extent of study - 1 in 20 (5%) AEP
Extent of study - 1 in 25 (4%) AEP
Extent of study - 1 in 50 (2%) AEP
Extent of study - 1 in 100 (1%) AEP
Extent of study - Designated flood event
Extent of study - 1 in 200 (0.5%) AEP
Extent of study - 1 in 500 (0.2%) AEP
Extent of study - Maximum channel capacity
Extent of study - Probable maximum flood
The Extent of Flooding lines are boundaries defining the expected location flooding would reach during a particular flood event (e.g. 1 in 100 (1%) AEP, etc.).
Note: To see the full scope of the floodplain mapping, 12 dataset layers are required to be loaded in the following order:
FLOODPLAIN DATASET LAYERS:
FPM Flood Level Points (m AHD)
FPM Flood Level Contours (m AHD)
FPM 1 in 100 (1%) AEP Floodway and Flood Fringe Line
FPM Extent of Flooding
FPM Levee Banks
FPM Location of Cross Sections
FPM 1 in 100 (1%) AEP Floodplain Development Control Area
FPM Map Index
FPM Bridges
FPM Special Development Condition Area
FPM 1 in 100 (1%) AEP Floodway and Flood Fringe Area
FPM Floodplain Area
The dataset covers the following areas:
Avon River - Toodyay to Beverley and Brookton Townsites.
Blackwood River – Augusta, Bridgetown, Nannup and Boyup Brook Townsites.
Brunswick River - Greater Bunbury
Bow River - Bow Bridge Townsite.
Capel River - Capel Townsite.
Cemetery Creek - Lake Grace Townsite
Chapman River – Geraldton Townsite.
Coblinine River & Dorderyemunning Creek - Wagin Townsite.
Collie River - Collie Townsite.
Denmark River - Denmark Townsite.
Fitzroy River - Fitzroy Crossing Townsite.
Five Mile Brook - Bunbury Townsite.
Gascoyne River - Carnarvon Townsite and the Lower Gascoyne (contains both pre and post-stage 2 Carnarvon flood mitigation works mapping: refer to "COMMENTS" field).
Greenough River – Indian Ocean to Walkaway.
Gribble Creek - Kalgoorlie Townsite.
Harding River - Roebourne Townsite.
Irwin River - Dongara Townsite.
Katanning Townsite.
Lower Collie River - Greater Bunbury.
Margaret River – Margaret River Townsite.
Nullagine River – Nullagine Townsite.
Preston River - Boyanup and Donnybrook Townsites.
Serpentine River, Peel, Birrega & Oaklands Drains, Murray River and the Peel Inlet / Harvey Estuary - Peel Inlet / Harvey Estuary to Pinjarra and south to the Darling Scarp (Murray River) and Peel Inlet / Harvey Estuary to Wellard (Peel Main Drain), east to South Western Highway (Serpentine River) and north to Wungong Brook (Birrega Drain).
Swan River, Canning River and Tributaries: Perth - Fremantle to Walyunga National Park (Swan River) and Canning Bridge to Brookton Highway (Canning River). Tributaries include Bennett Brook, Blackadder Creek, Ellen Brook, Helena River, Henley Brook, Jane Brook, St Leonards Creek, Susannah Brook (Swan River) and Southern River/ Wungong Brook (Canning River).
Toby Inlet – Quindalup Townsite.
Turkey creek - Warmun Aboriginal Community.
Vasse-Wonnerup Estuaries, Broadwater and New River - Busselton Townsite.
Wagin Townsite.
Willyung Creek – Albany Townsite.
Yakamia Creek – Albany Townsite.
The dataset also covers the following areas:
However, these are not design flood events, they are major historical or alternative scenario flood events that have been used (instead of the design flow, if present) to set planning & development guidelines as part of the floodplain management strategy. Refer to "FPM Historical Extent of Flooding" metadata for more details.
Bandy Creek - Esperance Townsite.
Cohn Creek - Merredin Townsite.
Corrigin Townsite.
Gordon River - Tambellup Townsite.
Turkey Creek - Warmun Aboriginal Community (contains both design and historical information).
Yakamia Creek – Albany Townsite (contains both design and alternative scenario information).
For further information on flooding and floodplain management in Western Australia please refer to our Water Facts publications: Flooding in Western Australia (Water facts 13) and Floodplain Management (Water facts 14).
This information is available at the following addresses:
https://www.wa.gov.au/system/files/2022-11/Water-facts-14-Floodplain-management.pdf https://www.wa.gov.au/system/files/2022-11/Water-facts-14-Floodplain-management.pdf
Glossary:
Annual exceedance probability (AEP) - the likelihood of occurrence of a flood of a given size or larger in any one year; usually expressed as a percentage.
1 in 100 AEP flood - this means that there is a 1 in 100 (or 1%) chance of a flow of this size or larger occurring in any one year. This flood has a 50% chance of being experienced at least once in a person's lifetime. The 1 in 100 AEP flood has been generally adopted in Australia and overseas as the basis for floodplain management planning.
Floodplain - the portion of a river valley next to the river channel which is covered with water when the river overflows its banks during major river flows. The term also applies to land adjacent to estuaries which is subject to flooding.
Designated flood event (DFE) - used for planning purposes and is generally the 1 in 100 (1%) AEP "designed" flood event. However, a designated flood event could be based on an "actual" flood event (e.g. Moora 1999 flood event) or an alternative scenario (i.e. Yakamia Creek - 1 in 100 (1%) AEP flood event plus sea level rise).
Maximum channel capacity (MCC) - the maximum flow that a waterway can contain before breaking out across the floodplain during a flood event.
Probable maximum flood (PMF) - the largest flood that could conceivably occur at a particular location, resulting from probable maximum precipitation. The PMF defines the extent of flood-prone land. Generally, it is not physically or financially possible to provide general protection against this event.
Australian Height Datum (AHD) - is a geodetic datum for altitude measurement in Australia. It was adopted in 1971 by the National Mapping Council as the datum to which all vertical control for mapping is to be referred. The datum is based on the mean sea level (1966-1968) being assigned the value 0.000m on the Australian Height Datum (AHD) at 30 tide gauges around the coast of the Australian continent.
