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 10 polygons illustrating the area of land adjacent to a water body which is subject to flooding during a range of possible design events:

1 in 10 (10%) AEP floodplain 1 in 20 (5%) AEP floodplain 1 in 25 (4%) AEP floodplain 1 in 50 (2%) AEP floodplain 1 in 100 (1%) AEP floodplain Designated flood event floodplain 1 in 200 (0.5%) AEP floodplain 1 in 500 (0.2%) AEP floodplain Maximum channel capacity Probable maximum flood

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.

• Blackwood River – Augusta, Bridgetown, Nannup and Boyup Brook Townsites.

• Bow River - Bow Bridge Townsite.

• Capel River - Capel 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.

• Margaret River – Margaret River Townsite.

• Nullagine River – Nullagine Townsite.

• Preston River - Boyanup and Donnybrook Townsites.

• Serpentine River, 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 and east to South Western Highway (Serpentine River).

• Swan River, Canning River and Tributaries: 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, 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.

• 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).

Glossary:

• Annual exceedance probability (AEP) - the likelihood of occurance 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.

• Flood fringe - the area of the floodplain, outside of the floodway where development could be permitted provided it is compatible with flood hazard and building conditions provide an adequate level of flood protection. These areas are generally covered by still or very slowly moving waters during a 1 in 100 (1%) AEP flood.

• Floodplain - the portion of a river valley next to the river channel which is covered with water when the rier overflows its banks during major river flows. The term also applies to land adjacent to estauries which is subject to flooding.

• Floodway - the river channel and a portion of the floodplain where a significant flow or storage of water occurs during floods. If the floodway is even partially blocked then the natural flooding regime of th area may be detrimentally impacted with flood levels being raised and affecting areas which may not have been previously affected. Development in floodways is to be avoided wherever possible.

• 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.

This dataset was formally known as FPM Floodplain Area (DOW-054)