The long cycle of Floods
The catastrophic floods in Queensland has brought great stress and sadness to those suffering loss of family and friends and property. It is only at these times people examine the history of floods and the long time gaps between the most catastrophic of these events. It also highlights the few people who carry personal memories of past events to prepare them for a similar current crisis.
The last catastrophic flood in Brisbane was in 1974 (and 1890 before that) as can be seen from the history chart of flood peak from the bureau of metrology http://www.bom.gov.au/hydro/flood/qld/fld_history/brisbane_history.shtml The current population of Brisbane and other parts of south-east Queensland has changed greatly in the 37 years since 1974. This state has the highest interstate migration flows.
Over the long term, Queensland interstate net migration has averaged additions of between 20,000 and 40,000 per annum (or about 1%pa of the population). This net migration allows for people moving in from other states (about 3% of the population) less those moving out of the state (about 2% of the population) – i.e. total turnover is 5%pa. In 1974 there were 2.0 million people in Queensland – there are now 4.5 million. Of these 4.5 million, we have calculated that only 350,000 (or 8%) were living in Queensland in 1974 and still living there in 2011. If these numbers are also representative of Brisbane, only 8% of residents could be expected to remember what the 1974 flood was like.
This highlights the lack of experience for people in a high migration and mobile workforce country like Australia, to assess flood risk in environments they live in. It places greater responsibility on Governments and housing approval authorities to assist recovery from these catastrophes and to give closer attention to regulating where people live, regardless of what restraint of personal freedoms this might imply.
Posted Sunday, 16 January 2011
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