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Central Europe: Catastrophic Floods Refocus Attention On Role Of Dams

  • Jeremy Bransten

The devastating floods in Central and Eastern Europe have reignited debate over whether man's changes to the countryside -- especially the extensive damming of rivers in recent decades -- are not partly to blame for the scale of the destruction. Dams are often touted as an important element in effective flood control. But the residents of Prague, Dresden, and scores of other smaller cities and towns who found themselves underwater last week are asking why the dams did not save them from catastrophe.

Prague, 21 August 2002 (RFE/RL) -- Before last week, Prague's previous catastrophic floods had been in 1890. Then, the force of the oncoming water, swollen with tree trunks and other debris, punched large holes in the city's landmark Charles Bridge.

This time, the medieval bridge survived, but many historic buildings were not so fortunate, as entire neighborhoods were inundated. Thirteen people in the Czech Republic lost their lives. The scene repeated itself downstream in Dresden and many other communities on the Czech and German sides of the border, following a pattern set a few days earlier in Austria and southern Bohemia.

As rescue crews and residents across the region begin the cleanup and governments count up the cost of reconstruction, much soul-searching is being done -- and questions are being asked. Conventional wisdom was that, at least in major cities such as Prague, an 1890-style flood could not reoccur, thanks to the many river dams built over the past decades.

So did something go wrong, or was conventional wisdom simply incorrect?

Humans have always lived near rivers, and periodic floods have been part of the natural cycle. Many factors go into making a flood, among them potential snow cover in the mountains, temperature, precipitation, soil permeability, ground slope, ground cover, and river-basin size and shape.

But during the middle and latter part of the 20th century, many rivers in Central and Eastern Europe literally changed their shape due to dams, which engineers promised would not only facilitate navigation and produce cheap electricity but also provide more security. On the first two counts, the engineers were right, but faith in their ability to eliminate or control floods -- in the wake of this summer's devastation -- has been seriously eroded.

Alexander Zinke heads an environment consultancy firm in Vienna that specializes in water management. He tells RFE/RL that attitudes in Central Europe -- especially Austria -- have been changing for the past decade and that this year's floods may prove to be the catalyst for real change: "The period of human development of nature where man was fighting against rivers and tried to tame rivers -- this period has ended. The peak was perhaps in the 1950s and '60s. Today, many river engineers have understood that they can only make sound river management if they cooperate with the natural forces of rivers."

Zinke says that dam construction, concentrated on the upstream section of rivers, has made navigation and electricity generation easier -- and thus provided economic benefits. But those benefits came at increased risk to downstream areas, which have become increasingly populated. "In these areas, the flood risk was in fact only further extended downstream and that resulted in a kind of chain reaction -- the flood risk was increased the more one looks downstream. So, the economic benefits of river development did not really take care to reduce the flood risk along the entire river length but only in the upper and middle part."

Because dams cannot be built effectively in lowland areas, and marshland and forests -- which used to act as sponges -- have been consistently reduced to make way for human settlement, there is little that stands in the way of floods, once they have made it past upstream reservoirs. The solution -- clearing lowland flood plains of humans so the soil can once again perform its natural absorption function -- is obvious, but has until now been resisted by governments, for obvious reasons.

"This is, of course, a very sensitive and difficult issue. Until now, river management authorities were always trying to prevent this dispute and were looking for spaces outside of settled areas. So we were looking for areas where still only agricultural or forested land was available to restore or to extend the flooding areas. But with the new floods, which we are presently experiencing in various countries, the discussion has now started that also settlements -- we are talking more about single farms or single houses, even single industry sites -- should be relocated and that the state should recompense these relocations."

Ladislav Satrapa, deputy head of the Hydrotechnical Department at the Czech Technical University in Prague, agrees that the relocation of single farms or businesses can be attempted in some areas. But he tells RFE/RL that the idea that entire lowland regions can be re-landscaped is simply impractical: "It would be complicated or practically impossible to replace the effect of the dams by changing current land usage and the face of the present landscape."

Satrapa argues that dams can, in fact, provide a certain degree of flood protection -- it all depends on how they are used. Most dams, by their very nature, serve contradictory aims: industry wants them to be kept full so they can generate electricity and improve navigation, while residents of lowland areas want them kept largely empty so they can retain floods. Both goals are achievable, Satrapa says, but not at the same time. Choices have to be made.

"This contradiction exists, of course. It exists because criteria such as the manufacturing of electricity, the supplying of industry with water, or the raising of the river's level to improve navigation are relatively easily quantifiable economically, whereas the effects of flood damage are more difficult to quantify. That's probably why the two sides of the equation haven't really been examined. Maybe if an economic study were made of the potential damage from floods, we would see that it would make economic sense to empty dam reservoirs to a greater degree, even if the economic effect is detrimental in the short term."

In the Czech Republic alone, the bill for flood reconstruction from floods in 1997 totaled some 2 billion euros. This year's destruction is expected to top 3 billion euros. And this does not factor in lost revenue from tourism or businesses left idle. Austria faces a similar bill while, Germany's damage will be higher.

Satrapa believes that in the Czech Republic, a detailed analysis of past floods, including the 1890 calamity, can provide authorities with valuable data on water levels, speed and trajectories, which can be used to calculate precisely the way in which dams can be used to better safeguard lowland communities.

"This can all be calculated with models. The dams can be factored out of the model and the causes can be found. The flood of 1890 happened along the same route as this current flood, and in 1890 there were no dams. But we can model this. We can say, 'We have the river, but we don't have the dams,' and we can trace the flow. And then we can factor in the dams and calculate what effect they would have on the flood."

Coordinated releases of water from a series of dams along a river like the Vltava, which runs through the Czech Republic for several hundred kilometers from south to north, is a difficult procedure that must be precisely choreographed. But Satrapa is convinced it can be done effectively -- using formulas developed by his department.

"Releasing water from these dams is a complicated thing, but in an ideal situation, if the system works as intended, the reservoirs should start to take in water at the point when the culminating flow is approaching. Before that, water in large amounts has to be released from the dams so that they can be filled by the culminating wave, and then there should be enough capacity to catch most of the flow."

Satrapa says this month's floods demonstrated that engineers largely failed to manage the coordinated intake and release of water in time, partly because dam levels were too high at the outset -- for economic reasons -- and partly because they had insufficient data on the way the river would behave.

Alexander Zinke in Vienna is more skeptical. For him, this month's Central European floods are further proof that engineers will never be able to time Mother Nature correctly. "The question with having large dams for flood retention is that you never know exactly when you should fill them and when you should release water, and that was also the problem with the present flood situation."

For the next few months, regional and national leaders in Austria, Hungary, Germany, and the Czech Republic will be focusing their attention on immediate reconstruction priorities before the onset of winter. But once the physical damage is repaired, major decisions on land and dam use await -- decisions which until now have always been avoided, but can probably no longer be put off.