Viv Forbes ("Flood plains are for floods", 26/3) makes the point that "those who choose to build on flood plains must bear the costs of the occasional flood". This seems reasonable at first, but Mr Forbes forgets that the blocks on flood plains were cheaper and are owned by those least able to pay high insurance premiums.

Many would assume that planning approval provides security against flooding. It is the planners and councils who approved the developments on the flood plains that should pay. Class actions are likely.

Another point Mr Forbes may not realise is that floods are less likely to be "occasional" as he claims. The bureau of meteorology modelling shows that under the current "high-emissions scenario", major rainfall disruptions will occur more frequently.

Finally, in the same way that fuel-reduction burns cannot stop bushfires in extreme conditions, the "flood-proofing" everywhere, called for by Mr Forbes, isn't effective or even possible. The total amount of water entering the Warragamba Dam during the rainfall event will exceed the additional capacity that the proposed extra three metres wall-extension would provide by 50 percent.

The amount of water going over the dam in one day alone reached 500 GL, the capacity of Sydney Harbour. As they say in medicine, "prevention is better than cure."

Spending money to keep global warming below 1.5 °C is the prevention we need.

Ray Peck, Hawthorn