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Searching for anti-flood solutions

THREE hours of intense rain earlier this summer in the village of Píla, near Častá in western Slovakia, seriously damaged local houses and destroyed nearby bridges, again reminding Slovaks of the destructive power of water. This was not a one-off occurrence of extreme weather, but the latest in a series of event that have struck all parts of the country over recent years and left local authorities scrambling to find a solution. However, experts appear to be split over what is the best response to extreme weather events. This is reflected, in a simplified form, by quarrels between the so-called ‘cement lobby’ – who favour large-scale interventions such as the construction of flood defence walls – and conservationists – who tend to prefer smaller-scale, nature-based solutions – over what forms of flood protection are more effective.

Píla, one month after heavy rain and floods damaged the village. (Source: Sme – Gabriel Kuchta)

THREE hours of intense rain earlier this summer in the village of Píla, near Častá in western Slovakia, seriously damaged local houses and destroyed nearby bridges, again reminding Slovaks of the destructive power of water. This was not a one-off occurrence of extreme weather, but the latest in a series of event that have struck all parts of the country over recent years and left local authorities scrambling to find a solution. However, experts appear to be split over what is the best response to extreme weather events. This is reflected, in a simplified form, by quarrels between the so-called ‘cement lobby’ – who favour large-scale interventions such as the construction of flood defence walls – and conservationists – who tend to prefer smaller-scale, nature-based solutions – over what forms of flood protection are more effective.

On August 18, scientists from the Institute of Hydrology at the Slovak Academy of Sciences tested some alternative anti-flood measures in Ťahanovce, close to Košice. The experience of flooding in Píla was also used to inform the tests. Experts found that in Píla, a tiny village built in a narrow valley with a brook running through it, forest roads in the Small Carpathians above the village had channelled rainwater directly into the village.

During the test in Ťahanovce, the experts imitated conditions from Píla in terms of the amount of water that had fallen. Apart from ‘traditional’, compacted-surface forest roads, they tested a forest road with a ploughed-up surface and one with small wooden dams installed.

The test was spurred by Ján Nigut, the mayor of Ťahanovce, after he became frustrated by quarrels between the ‘cement lobby’ and conservationists over which anti-flood solution was more effective, the Sme daily wrote.

Part of Ťahanovce is typically flooded every year by the local brook, which takes rain water from a nearby hill towards dwellings. In response, the mayor decided to build a system of small water dams.

“The water management company, Slovenský Vodohospodársky Podnik, claimed that it did not have money to regulate the brook,” Nigut said, as quoted by Sme. “This indirectly pushed us towards alternative solutions. We did not want to wait for the next flood.”

Nigut is convinced the combination of alternative solutions since applied has prevented another flood from occurring in his village this year.

In the Ťahanovce test, the traditional forest road retained 19 percent of the falling water. Wooden dams retained 33 percent of water. But the ploughed-up road, although it was no longer usable as a road, retained 100 percent of the water.

Michal Kravčík, a hydro-ecologist and the father of the idea of anti-flood small terrain adjustments, agrees that forest roads with a compacted surface significantly worsen the ability of the land to retain rain water.

But he regards the experiment in Ťahanovce as not having been independent – or even valid. He wrote in his blog that scientists tested and compared two measures which are not related: transformation of compacted-surface forest roads and construction of small dams.

Anti-flood measures

After taking power last year, Prime Minister Iveta Radičová, to the displeasure of water managers, supported the solutions proposed by conservationists. The government started the Landscape Revitalisation and Integrated River Basin Management Programme, whose first project is just underway. Under this project, 190 villages were chosen from the more than 830 that expressed an interest. In these, various measures and landscape adjustments were applied that should result in the retention as much as 6 million litres of rain water, i.e. at least 30,000 litres per village.

The experiences of villages involved in the project have been very good, with mayors that were canvassed evaluating the measures very positively, Kravčík said, as quoted by the SITA newswire in late July. Based on a survey among the participating villages, almost half said that the project had helped reduce flood risks and those in localities where works had already been carried out said the measures had proved successful after heavy rains. By late July 2011 some villages had completed 70 percent of the planned works, while others had finished only 20-30 percent.

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