Floods: Wivenhoe, dams and bigger issues

Recriminations are continuing over the management of the Wivenhoe dam and its contribution to the devastating February floods in Brisbane. Few, however, are looking at the evidence that is mounting of the considerable costs involved in the construction and failure of large dams.

Recriminations are continuing over the management of the Wivenhoe dam and its contribution to the devastating February floods in Brisbane. Few, however, are looking at the evidence that is mounting of the considerable costs involved in the construction and failure of large dams.

The insurance industry has commissioned its own report on Wivenhoe’s management. Consultant engineering firm WorleyParsons attributes at least some of the blame to Queensland government-owned Seqwater for the way in which floodwater releases from the dam were managed during the crisis.

Arguably there are broader issues. Wivenhoe is a classic example of the many white-elephant engineering projects backed by the notorious reactionary Joh Bjelke-Petersen, National Party premier from 1968 to 1987. Built after the 1974 floods, Wivenhoe is an earth and rock embankment wall 2.3 kilometres long and 50 metres high. The dam’s reservoir has a total storage capacity of 2.61 cubic kilometres. Its surface area is 109.4 square kilometres. The cost at the time was $450 million.

‘Mythical’ flood control

Opposition to the dam was muted and came mostly from farmers whose land was compulsorily acquired for construction. The constant refrain was that the dam was needed to stop a repeat of the 1974 Brisbane flood. Indeed, as a federal government-commissioned risk assessment of natural disasters noted in 2000, an “urban myth” had emerged about the protective capabilities of the dam. The consultants noted prophetically:

“There is a widely held view within the Brisbane community, for example, that the construction of Wivenhoe Dam will prevent a repetition of the 1974 flood, and consequently, Brisbane is now flood-free.

“Whilst Wivenhoe Dam has undoubtedly improved the management of flood waters, it certainly will not eliminate all floods in the Brisbane River, let alone floods originating in the Bremer River portion of the catchment.”

Moreover, according to the Australian, the body responsible for managing large dams - the Australian National Committee on Large Dams - the dam did satisfy the criteria for acceptable flood mitigation measures in 2007.

Yet Wivenhoe is not an isolated example. There have been many cases of large dams - defined as dam walls measuring above 15 metres - failing. As one World Wild Life Fund study notes, there are more than 45,000 large dams in more than 150 countries. There is some evidence that large dams have improved agricultural output by making more land suitable for cropping through the provision of water for irrigation. They have also provided some flood control and hydropower.

Costs

There are considerable doubts, however, about the reliability and effectiveness of these benefits in proportion to the costs. Patrick McCully in his book Silenced Rivers: The Ecology and Politics of Large Dams discusses many of these failures. The most spectacular was the Henan disaster in central China in August 1975. As many as 230,000 people may have died as a result of dam failure. Many other disasters have occurred since the 1860s.

Dams have also caused considerable environmental damage and, together with associated activities such as irrigated agriculture, have been a major cause of the decline of freshwater biodiversity. Dams create major obstacles for fish populations and disrupt breeding patterns. So-called fish ladders and other technologies are usually just for show. Dams block the flow of sediment into estuaries, creating “hungry rivers” and reducing estuary biodiversity and sustainability. Reservoirs often inundate sensitive environmental areas and valuable crop land. Wivenhoe submerged prime farmland capable of producing millions of dollars of output.

Human populations often feel some of the most extreme impacts. In her pamphlet The Cost Of Living, Arundati Roy estimates that in India alone, some one and a half million people have been displaced since independence. Even apparently benign benefits such as hydropower have been shown to be costly and of little benefit.

Perhaps the most damaging flow-on affect of large dams is the impacts of mass irrigation systems. Such schemes usually have a lifespan of one to two generations as wasteful irrigation raises water tables, leading to land degradation. The disaster of Australia’s Murray-Darling system is a graphic example.

Admitted failures

By the year 2000 even the World Bank - a major sponsor of large dams - concluded through its World Commission on Dams that many of its projects had been failures. It concluded: “… on balance, the ecosystem impacts are more negative than positive and they have led, in many cases, to significant and irreversible loss of species and ecosystems.”

Its conclusions on technical and economic impacts of large dams included: “ … irrigation services have typically fallen short of physical targets, did not recover their costs and have been less profitable in economic terms than expected.

“… municipal and industrial water supply have generally fallen short of intended targets for timing and delivery of bulk water supply and have exhibited poor financial cost recovery and economic performance.

“… [large dams] have led to greater vulnerability to flood hazards due to increased settlement in areas still at risk from floods, and in some cases have worsened flood damages for a number of reasons, including poor operation of dams.”

The last part is particularly telling in the case of Brisbane. Wivenhoe created a false sense of security.

Much large dam construction is now confined to the developing world. As McCully notes, often the motivation for their construction - as well as coming from engineering and construction firms’ desire for profit - can come from Third World leaders (and the Stalinist Soviet and Chinese leaderships) who want to make “visible” signs of development.

The Queensland Conservation Council is running a campaign against dam building. Currently the government is proposing or constructing 11 major new dams in the state.

Alternatives

Increasingly alternatives to large dams are emerging. More efficient irrigation systems are available. Better use of drinking water and harvesting of storm and waste water offer viable alternatives to new dams and reservoirs.

For flood management, the International Rivers Network notes there is an increasing need to move to “softer” strategies in place of large-scale engineering fixes:

“Strategies to reduce the speed and size of floods include moving embankments back from rivers and restoring wetlands, floodplains and meanders, and slowing down urban run-off.

“… Discourage people from living in the areas most vulnerable to floods. Floodplain management includes planning regulations to discourage new floodplain development, and financial incentives for people living in the riskiest areas to move to higher ground.

“Flood risk management includes structural measures such as flood-proofing of individual buildings (for example, by raising them on stilts or mounds) and communities (e.g., building flood shelters and flood-protected water sources), the building of floodplain storage and bypass systems (areas of sparsely or undeveloped land which can be used to divert or store high floods), and the judicious use of well-maintained embankments for vulnerable urban areas.”

Such measures would require a major reordering of economic priorities. That is unlikely to come about while many of the decisions are dictated by profit-driven construction and engineering firms.