Floods don't occur randomly, so why do we still plan as if they do?

phys.org | 3/19/2018 | Staff
TitanSwimr (Posted by) Level 3
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The South East Queensland study area (approximately indicated by the orange box) and the 10 catchments analysed in this study.

Most major floods in South East Queensland arrive in five-year bursts, once every 40 years or so, according to our new research.

Estimation - Protection - Management - Approaches - Basis

Yet flood estimation, protection and management approaches are still designed on the basis that flood risk stays the same all the time – despite clear evidence that it doesn't.

We analysed historical flooding data from ten major catchments in South East Queensland. As we report in the Australasian Journal of Water Resources, 80% of significant floods arrived during five-year windows, with 35-year gaps of relative dryness between.

Succession - Floods - South - East - Queensland

The early 1970s brought a succession of severe floods to South East Queensland. This was followed in the 1980s by a raft of floodplain development projects, together with extensive research on floodplains and flooding risk, carried out by a group of researchers who described themselves as the "Roadshow" because of their frequent visits to flood-prone regions.

Throughout the 1980s, some Roadshow members noticed that large floods in South East Queensland seemed to follow a 40-year cycle, with five-year periods of high flood risk separated by 35 years of lower flood risk. They speculated that the next "1974 flood" (a reference to a devastating flood that hit Brisbane and South East Queensland that year) would arrive some time around 2013 .

South - East - Queensland - Floods - January

Sure enough, South East Queensland was once again hit by large floods in January 2011 and January 2013.

Evidently, large floods in South East Queensland are not random. This is a problem, given that development policies and engineering practice, by and large, still assume that they are.

Queensland - Meteorologist - Farmer - Inigo - Jones

In 1931, the Queensland meteorologist and farmer Inigo Jones linked the Brisbane River's floods to the Bruckner Cycle of solar activity, which he determined to be 35 years long, but which has...
(Excerpt) Read more at: phys.org
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