The Tongan volcano may well have contributed to the 2022 flood event, as suggested by John Scrivener last week, but we would be taking a great risk in excluding it from our flood planning.
The underwater volcano made a one-off injection of a large amount of water vapour into the atmosphere, but climate change is doing this all the time. By increasing the sea surface and atmospheric temperatures, it is increasing evaporation and the amount of water vapour the atmosphere can hold.
This increases the amount of rain that can, and does, fall. I have plotted 125 years of the highest one-day rainfalls each year for Mullumbimby, and before 2022 it shows a 20 per cent increase in the average rainfall and a 60 per cent increase in the most extreme events. Including 2022 the figures are 25 per cent and 90 per cent respectively.
This shows that although the 2022 event was extreme, it was a further contribution to a rising trend. It is not the 2022 flood itself that needs to be taken into account in our planning, but future projections of that rising trend.
Byron Council is not doing this – they continue to ignore the lessons of the 2022 flood by relying on the 2020 flood study, with a token and long-outdated increase in rainfall for future planning.
The state government’s report on the 2022 flood found that we needed a complete new flood study to include the lessons of 2022, but it will take several years to get the funding and complete the study.
In the meantime, we, the community, do not even know how high the 2022 flood was in most areas – these figures are still being kept secret. Someone planning to build in a flood-liable area may not realise that the minimum floor level required by Byron Council may be only 100 or 200mm higher than the last big flood.
We can hope that the 2022 flood was a one-off event, but we need to assume that it was an indicator of what may be to come and plan accordingly, as governments continue to approve new coal mines and gas fields.
For four decades The Echo has printed the stories some people loved, some people hated, and some pretended not to read. If you want us to keep telling the truth, the real truth, not the sugar-coated version. We’ll need your support to keep the presses rolling. 
