FPM Historical Extent of Flooding (DWER-123)

Historically, low-lying land adjacent to rivers and coastlines has been favoured for settlement as they provided sources of fresh water, food, transportation and waste disposal. These areas become affected by flooding during sufficiently heavy or prolonged rainfall, high tides or storm surges and cyclones. In the north-west of the State flooding is most likely to be caused by the summer monsoon or tropical cyclones while floods in the south-west are more likely to occur in response to heavy winter rainfalls. While historical flood records and information extend as far back as 1830, detailed information on peak flood levels is typically limited to the last few decades. This dataset shows the extent of flooding (polylines) that has occurred during major flood events in Western Australia. Note: To see the full scope of the historical flood mapping, 3 dataset layers are required to be loaded in the following order: FLOODPLAIN DATASET LAYERS:
FPM Historical Flood Levels (m AHD) FPM Historical Extent of Flooding FPM Historical Floodplain Area The major flood events that are covered in this dataset are: Bow Bridge Townsite (June 1988) Corrigin Townsite (January 1982) Esperance Townsite (January 2007) Kupungarri to Willare (including Dales Yard & Mount Joseph gauging stations) - Fitzroy River (January 2023) Lake Grace Townsite (January 2006) Merredin Townsite (February 1979) Perth (February 2017) Tambellup Townsite (January 1982) Warmun Aboriginal Community (March 2011) York Townsite (July 2021, August 2022) Other major flood events that have occurred in the past include: Blackwood River (1945, 1955, 1963, 1964, 1982) Collie River (1945, 1963, 1964, 1974, 1982) Fitzroy River (1983, 1986, 1991, 1993, 2002, 2011) Gascoyne River (1960, 1961, 1980, 1995, 2000, 2010) Greenough River (1888, 1927, 1953, 1971, 1988, 1999, 2006) Moore River (1934, 1955, 1961, 1995, 1999) Murray River (1862, 1945, 1955, 1964) Preston River (1964, 1967, 1974, 1983, 1990, 2011) Swan River (1862, 1872, 1945, 1955, 1964, 1983) The historical flood information is used in the Department of Water and Environmental Regulation’s floodplain management activities to ensure that floodplains are managed for the benefit of the whole community, minimising the risk and damages and protecting environmental values. Floodplain mapping datasets and floodplain development strategies for rivers and major watercourses in Western Australia are also available from the Department of Water and Environmental Regulation. 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.

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.