QUEENSLAND by Robert BomNews Weekly
After Cyclone Marcia: balancing drought relief and flood mitigation
, March 28, 2015
The onslaught of Queensland’s Cyclone Marcia on February 20 led to a mistimed release of water at the Callide Dam near Biloela in central Queensland, causing serious flooding and great damage to homes and farmlands. Locals are searching for answers.
The Callide Dam in
In a way, the event is part of a much wider problem in the Fitzroy River catchment area. Ultimately, it comes back to the issue of balancing the growth of human needs against the fickleness and incredible forces of nature.
For authorities in our part of the world, the problems of balancing the unpredictable weather, and trying to outguess and control the need and supply of water, are tasks that may be too hard for any authority to perform without making mistakes.
Fertile low-lying land round Biloela and down-river depends on a reliable supply of water for successful farming. In the past, before the Callide Dam was constructed, it was common to experience floods. A sibling of mine recounts sitting at the Jambin pub, with his legs in water, having a drink at the bar, together with other travellers caught up a major flood.
Releasing water too early could cause a “Tinaroo” effect. Some 20 years ago, authorities emptied the Tinaroo Reservoir dam in far north Queensland in preparation for what was generally regarded as very dependable summer rains in the area around Cairns. The rains failed that year, and the area was caught in a nasty drought until the next year’s rains came.
After recent Cyclone Marcia, residents of the Callide Valley can rightfully point to authorities not acting early enough to reduce the Callide Dam’s water level. On the other hand, water authorities can argue that, owing to the unpredictable path of Marcia, the cyclone could easily have veered away from the Callide Valley without causing any flooding.
Over the last 30 or so years, the region has been particularly dry, as major rain events in central Queensland have skirted around the Callide catchment area. After the dam was built, it took about 30 years for the dam to fill.
Both Canberra and the Queensland government need to take a good look at the Callide Dam fiasco and consider compensation payments in order to avoid costly legal action against water authorities by locals affected by the flood. A failure to do this can only mean that either nothing will be done or an injustice will be perpetrated.
Either way, it will impose considerable costs on people who do not deserve it.
That brings me to the wider problem of flooding in the Fitzroy River catchment area, which includes the Callide Valley. This catchment area is the second largest in Australia, with some seven river-systems flowing ultimately into the Fitzroy River.
The Fitzroy River flows through the regional city of Rockhampton, about 45 kilometres from the coast. Since European settlement, the highest flood was in 1918, with the river peaking at 10.3 metres. Queensland’s newsworthy 2011 flood peaked at 9.3 metres.
In Aboriginal folklore, indigenous Australians have seen much higher floods. Central Queensland University has confirmed the capacity for flooding could see a peak of 12.2 metres in the Fitzroy River.
In such large floods, the Aboriginal population fled to the hills. The area most prone to flooding is South Rockhampton, where the only high ground is the Athelstane Range and Wandal Hills. It is a sure bet that motor vehicles would be granted priority space on the hills, with little room for people, in the event of a major flood.
Rockhampton’s two bridges are built to accommodate 10.3 metre floods, but the approaches on either side of these bridges are subject to flooding. Almost all the city’s medical facilities, especially hospitals, are concentrated in South Rockhampton. The city’s airport is prone to flooding.
In a very big flood, South Rockhampton would be entirely isolated.
The city needs a lifeline road that could be provided by linking the southern tip of the Athelstane Range to a suitable higher spot in North Rockhampton. The main bridges across the Fitzroy River need to be about three metres higher. The city also needs an all-weather landing-strip on the northern side of the river, reasonably close to the city, in order to keep communications and supply-lines open during a major flood.
Another proposal has been to build a 10-trillion-litre dam for flood mitigation and boost the water supply for industry and agriculture.
Such a scheme was originally proposed some decades ago by the famous engineer, Dr John J.C. Bradfield (1867-1943), who oversaw the design and construction of the Sydney Harbour Bridge.
Just recently, an aspiring local revived the proposal in a big way with full-page advertisements in the local paper. He was backed by one of Australia’s foremost graziers, Sir Graham McCamley.
However, would a 10 trillion-litre dam be sufficient? The ordinary high 9.3 metre flood we had in 2011 produced three times that volume of water. Higher floods would swamp a much wider region around Rockhampton.
Some people have proposed that, in the event of flooding, air access could be switched to the military airport north of Rockhampton and Byfield.
However, this is where Cyclone Marcia made landfall. This is not a good suggestion.
Robert Bom lives in West Rockhampton, Queensland.