It’s been an oft repeated statement that more properties were flooded in the 2011 Brisbane floods than in 1974 despite the flood peak being a metre lower. As part of something I’m working on I decided to look further into it.

As it turns out the information available is not exactly clear. There’s a vast difference between having floodwater in your yard and having it in your house. Particularly when a source is quoted elsewhere it’s very easy for the meaning of the number to be changed. Also the source and assessment methodology is generally not listed when these numbers are quoted in reports. Here’s the numbers as best as I’ve been able to find them.

In Ipswich it looks like marginally fewer homes and businesses were flooded in 2011 than in 1974. In Brisbane though more homes were affected by flooding, it seems that fewer had water inside them.

What is indisputable is that far fewer people died in Greater Brisbane in 2011 than in 1974.

References

If anyone can find me better sources, including those that make clear how they counted and what their definitions mean please let me know in the comments.

Report by Director of Meteorology, Brisbane Floods January 1974, Bureau of Meteorology, Canberra

Queensland Floods Commission of Inquiry Interim Report, Chapter 1, QFCOI, Brisbane

Independent Review of Brisbane City Council’s Response to the January 2011 Flood

Ipswich City Council, Community Recovery Plan

Brisbane City Council 12 Month Flood Recovery Report