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 8 extent types as follows:
1 in 10 (10%) AEP flood level contour
1 in 20 (5%) AEP flood level contour
1 in 25 (4%) AEP flood level contour
1 in 50 (2%) AEP flood level contour
1 in 100 (1%) AEP flood level contour
Designated flood event level contour
1 in 200 (0.5%) AEP flood level contour
1 in 500 (0.2%) AEP flood level contour
This dataset describes how flood levels vary across the floodplain for various sized flood events. Flood levels are referenced to the Australian Height Datum (AHD)
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 - Brookton Townsite.
Collie River - Collie Townsite.
Fitzroy River – Fitzroy Crossing 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.
Katanning Townsite.
Lower Collie River, Brunswick River and Wellesley River - Greater Bunbury.
Preston River - Donnybrook Townsite.
Serpentine River, Peel, Birrega & Oaklands Drains, Murray River and the Peel Inlet / Harvey Estuary - Peel Inlet to the confluence of the Dandalup-South Dandalup-North Dandalup Rivers and south to the Darling Scarp via Pinjarra (Murray River), Peel Inlet to Black Lake (Nambellup Brook) and Geogrup Lake to South Western Highway (Serpentine River), north to Wellard (Peel Main Drain) and 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).
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 life time. 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.
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.
