FPM Location of Cross Sections (DWER-022)

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 environmental and ecological considerations are not addressed.

This dataset contains the location of cross sections lines, indicating modelled / surveyed cross sections of the river channel and floodplain.

The cross sections are labelled using chainage, which is generally defined as the distance from the downstream start of a flood study traversing up the river. The cross sections are defined perpendicular to the flow direction and illustrate how the relevant flood levels are to be applied across the floodplain.

Each cross section has an associated flood level listed in the attribute fields as follows:

FLDLVL_10 (1 in 10 (10%) AEP flood event) FLDLVL_20 (1 in 20 (5%) AEP flood event) FLDLVL_25 (1 in 25 (4%) AEP flood event) FLDLVL_50 (1 in 50 (2%) AEP flood event) FLDLVL_100 (1 in 100 (1%) AEP flood event) FLDLVL_DFE (Designated flood event) FLDLVL_200 (1 in 200 (0.5%) AEP flood event) FLDLVL_500 (1 in 500 (0.2%) AEP flood event) FLDLVL_MCC (Maximum channel capacity) FLDLVL_PMF (Probable maximum flood event)

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.

• Capel River - Capel Townsite.

• Chapman River – Geraldton Townsite.

• Coblinine River & Dorderyemunning Creek - Wagin Townsite.

• Collie River - Collie Townsite.

• Corrigin Townsite.

• Denmark River – Denmark Townsite.

• Five Mile Brook - Bunbury Townsite.

• Fitzroy River - Fitzroy Crossing.

• Greenough River – Indian Ocean to Walkaway.

• Gribble Creek - Kalgoorlie Townsite.

• Harding River – Roebourne Townsite.

• Irwin River - Dongara Townsite.

• Margaret River – Margaret River Townsite.

• Murray River - Ravenswood Bridge to Blythewood.

• Nullagine River – Nullagine Townsite.

• Preston River - Boyanup and Donnybrook Townsites.

• 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.

• Yakamia Creek – Albany Townsite.

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.

This dataset was formerly known as FPM Location of Cross Sections (DOW-035)