Dams can pose security risk to Africa
Dams pose security risk to Africa
A Dangerous Path: Dams pose flood risks in a warming world
Patrick McCully, Executive Director of International Rivers
October 5, 2007
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Floods are the most destructive, most frequent and most costly
natural disasters on earth. And they are getting worse. In recent
weeks, 14 African nations have seen their worst floods in decades.
More than a million people have been affected, over 200 drowned, and
countless others made homeless across the continent. At least some of
this suffering was preventable.
The recent flood disaster in Ghana was reportedly greatly worsened
when dam operators in Burkina Faso opened a floodgate to prevent the
Bagre Dam overflowing after heavy rain. That water raced downstream
to Ghana, through the Black and White Volta Rivers, hitting riverbank
dwellers hard. This is not the only time this has happened in Africa.
Hundreds of people were killed and hundreds of thousands harmed when
Nigerian dam operators opened their floodgates without warning in
1999 and 2001.
In these cases – and in many others the world over – dams supposed
to help reduce floods only made them worse. Yet a number of
governments in Africa and elsewhere are proposing more dams as the
answer to floods.
Flood damages have soared internationally in recent decades, partly
because global warming is leading to more intense storms, and partly
because more people are living and working on floodplains. The UN
estimates that by 2050 the number of people at risk of damaging
floods will double to two billion. But one key factor behind the
spiraling flood damages are the very flood control measures that are
supposed to protect us.
Dams and embankments can never be fail-proof, and when they fail,
they do so spectacularly and sometimes catastrophically. They provide
a false sense of security that encourages risky development on
vulnerable floodplains. Too often in the case of non-flood-control
dams, downstream residents are put at risk by agencies more intent on
wringing the most electricity or irrigation water possible from a
reservoir, rather than keeping water levels low enough to absorb
flood waters.
The limitations of conventional flood control will become ever more
evident as global warming-induced super-storms test dams and
embankments beyond their intended limits.
Author Jacques Leslie aptly describes dams as “loaded weapons aimed
down rivers.” Dams kill not only because of dam-operators’ negligence
and failure to warn people downstream when they suddenly open their
gates, but also because they collapse (as many as 230,000 people died
from a chain of dam failures in central China in 1975). Several large
dams have collapsed in Nigeria with deadly consequences, notably, the
Bagauda Dam in Kano State in 1988; the Cham Dam in Gombe State in
1991 and the Bagoma Dam in Kaduna State in 1994.
Conventional “hard path” flood control ignores the complex workings
of rivers and coasts. Dams, embankments and the straightening and
dredging of rivers trigger profound changes in the ways in which
water and sediment flow through watersheds. Flood damages soar when
engineering projects reduce the capacity of river channels, block
natural drainage, increase the speed of floods, and cause the
subsidence of deltas and coastal erosion. In addition, “hard path”
flood control often ruins the ecological health of rivers and estuaries.
There is a better way to deal with floods — the “soft path” of flood
risk management. Flood risk management assumes that all anti-flood
infrastructure can fail and that this failure must be planned for.
The “soft path” is also based on an understanding that some flooding
is essential for the health of riverine ecosystems.
Instead of spending billions of dollars vainly trying to eradicate
floods completely, we need to recognize that floods will happen and
learn to live with them as best we can. This means taking measures to
reduce their speed and size (for example, restoring meanders and
wetlands) and duration (e.g. improving drainage). It means protecting
our most valuable assets by raising houses on mounds or stilts, and
defending built-up areas behind carefully planned and well-maintained
embankments. It also means doing all we can to get out of floods’
destructive path with improved warning and evacuation measures.
Such practices are already in use in many parts of the world. In
China, efforts are underway to restore 20,000 square kilometers of
Yangtze wetlands to act as flood absorption areas. Artificial flood
releases are being tested in Nigeria as a means to revive wetland
ecosystems downstream from the Tiga and Challawa Gorge dams.
Alterations in water management are being proposed for Mozambique’s
Cahora Bassa Dam that could reduce the impact of major floods and
restore downstream ecosystems.
In the United States a 10-year project to reduce floods on the Napa
River in California will restore tidal marshlands, remove some
buildings from the flood zone and set back embankments to give the
river room to spread. Communities along France’s longest river, the
Loire, persuaded the government to scrap a planned “flood control”
dam in favor of river restoration and a new flood warning system.
Despite a growing worldwide consensus that mitigation, not
elimination, is the only realistic flood policy, there remain
powerful factions devoted to outmoded “hard” flood control. An iron
triangle of politicians, bureaucrats and dam builders continues to
promise salvation through embankments and dams after floods strike
(even when such floods have been worsened — or caused – by existing
dams and embankments).
Instead of adopting a method of flood management that has failed in
other parts of the world, Africa can learn from the mistakes of other
nations and adopt a more flexible, effective and sophisticated set of
techniques to cope with floods. Such an approach will provide greater
protection, at less cost, than engineered flood control, and more
flexibility for adapting to future climate changes.
Patrick McCully is the author of “Before the Deluge: Coping with
Floods in a Changing Climate” published by IRN. Download the report
at http://tinyurl.com/yo3oug