FPM Historical Flood Levels (m AHD) (DWER-122)

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 contains the available surveyed peak flood level information for major flood events that have occurred in Western Australia. The flood levels are referenced to the Australian Height Datum (AHD).

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

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.

Note: The ‘Event’ dates in the attribute table are derived from various sources, including Department of Water and Environmental Regulation's Floodplain Management Section reports, records and plans, historical newspaper articles, flood survey information, Bureau of Meteorology rainfall intensity records, on-site flood information and information provided by locals. It is not always possible to obtain an exact date when the flood event has occurred because in some cases the floodwaters may take several days to subside, peaking at different times at various locations over the course, or historical records may only refer to the month or year of the event.

However, considering the above date variations the ‘Event’ dates are listed as follows:   

22nd December 2010: The day, month and year of the flood event (or rainfall) are known.

August 1963: The month and year are known. Exact date unknown.

1954: The year is known but the month and day are unknown.

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.



Tags: Rivers Mapping, Rivers Monitoring, Rivers Research, Rivers Surveys, Water
Organization: Department of Water and Environmental Regulation