Floods a reminder not to gamble with the weather

I refer to the report “Downpour a $2bn disaster” (23/3) and other reports. The continuing deluge and floods are certainly disastrous, not just financially but also socially. Thousands of NSW residents have either been forced to desert their homes or have lost them to the record floods. Images of houses and livestock being carried away by raging flood waters will be imprinted on many minds.

According to the Bureau of Meteorology, the La Nina weather phase will finish by the end of May. However, the World Meteorological Organisation predicts that La Nina will be replaced in early November by an El Nino phase, which would bring dry, hot weather to eastern Australia. With rampant plant growth stimulated by the downpour, there will be a dire risk of another Black Summer of bushfires, which would have abundant fuel to feed on. Is Mother Nature warning us?

Douglas Mackenzie, Deakin, ACT

A significant advantage of using desalination plants is that it obviates the “Wivenhoe Dam dilemma”. Dam administrators have to balance allowing the dam to fill to maximum capacity to meet water supply benefits, against the problem that a full dam is vulnerable to additional flooding rain, with no ability to store more water as a flood mitigation measure.

The ocean is a stable and inexhaustible source of water for desalination, with no risk of flooding.

Richard Gorrell, Killara, NSW

The floods are a reminder not to gamble with our weather. There has to be built-in resilience to cater for over and under supply, especially close to CBDs.

So let’s not make the same mistake with our electricity supply. Imagine the chaos with an unreliable train network, an unreliable airconditioning system for places where we work , socialise and are entertained. And remember to apply some honest life-cycle costing to solutions.

Gordon Thurlow, Launceston, Tas

Ian Dinham’s interesting article (“In too deep: housing on the floodplain”, 23/3) mentions the one-in-a-100-year flooding of the downstream Hawkesbury-Nepean Valley. I had nothing to do with the design of Warragamba Dam, but I do know that the criteria for safety against dam failure once included the one-in-10,000-year upstream flood, more recently amended to the one-in-a-100-thousand-year flood for large dams. I believe that the same applied to earthquakes, for example, in California.

It is important to realise that “one-in-a-100-year” does not mean a frequency of 0.01 per year. It means a probability of one-in-a-hundred each year. It could be this year and might then be exactly the same next year. The precautions against such an event must be decided on the basis of the risk that society is prepared to take from such an event. How to estimate this probability is another subject.

Don Higson, Paddington, NSW

Ian Dinham’s excellent article is topical but only touches on one problem. From overall management of bushfires and floods to rejecting coal before its potential replacement is fully capable to forbidding a nuclear industry by legislation to ordering substandard or archaic defence equipment, and much else besides, the sheer dearth of plain common-sense among our politicians and bureaucrats at all levels of government is astounding. It presents a question: Would we be better putting them all in the enclosure at Taronga Zoo and letting the monkeys out ? Right now, no prizes for guessing the best answer.

Peter M. Wargent, Mosman, NSW

On Tuesday morning, a Brisbane-based ABC-TV reporter was in front of a semi-rural house and said words to the effect of “this house did not flood but its neighbour did”.

If you looked over his shoulder, it was obvious why the older property did not flood. It was built in the traditional way, a pole house on top of a mound — built to suit its location in an area with a history of flooding.

Lessons learned in the past but conveniently forgotten.

Alan Coulson, Umina Beach, NSW

The Windsor Bridge in NSW was finished in 2020 with the road level raised above expected future flood levels, but which is today under water. Was the rainfall consultant to the design team Tim Flannery, with further inspiration from the accountants in the finance department?

Brian Binskin, Eastwood, NSW