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The Swiss secret to dealing with floods

June 13, 2013
  • Switzerland suffered less from the 2013 floods than neighbor Germany
  • The Swiss have developped hazard maps since 1987
  • These maps focus on areas where actual damage can occur and breaks away from traditional focus on the whole area
  • For large scale rivers like the Elbe a holistic approach remains the best method however

In early summer 2013, people living near the lower reaches of the River Elbe and the Danube were fighting floods for weeks. Switzerland, on the other hand, coped with the floods better. Robert Boes, Head of the Research Institute for Hydraulic Engineering, Hydrology and Glaciology at the ETH (Federal Institute of Technology) in Zurich, explains the special flair that the Swiss have for dealing with natural hazards.

 

Allianz Open Knowledge: While the clean-up effort is beginning in the affected regions beside the Danube, and the Elbe is keeping northern Germany in a state of emergency, the Swiss media is reporting on how their country has successfully resisted the floods. What is it that the Swiss are doing better when it comes to flood protection?

Robert Boes: In Switzerland there's a lot of talk of integral risk management. This means identifying and assessing natural hazards. The key words here are 'hazard maps'. These are available for almost every municipality in Switzerland. These maps serve as a basis for conceiving systematic measures to protect the population. This system really got going in 1987.

 

Why 1987? What was happening then?

In the summer of 1987, the Swiss were hit by a large-scale flood that affected several regions. This happened after decades of hydrological peace and quiet. We'd felt safe until then. Over time, a lot had been built. But then the huge flood came - and with it, the recognition that nature can always find something bigger to throw at you. This flood had a great deal of impact on Swiss attitudes to flooding.

Robert Boes, Head of the Research Institute for Hydraulic Engineering, Hydrology and Glaciology at the ETH (Federal Institute of Technology) in Zurich: "In Switzerland, people are made aware of natural hazards.“
Robert Boes, Head of the Research Institute for Hydraulic Engineering, Hydrology and Glaciology at the ETH (Federal Institute of Technology) in Zurich: "In Switzerland, people are made aware of natural hazards.“

So the Swiss learned their lesson. What is the difference now between the German and Swiss attitudes to flooding?

Where hazard prevention is concerned, the Swiss are the world leaders. In terms of flood protection, we break with the old school by not concentrating on the whole area. We only protect those areas where damage can actually occur. In places with no increased risk of damage, the river is just given some space, if possible.

Perhaps the most significant difference in terms of the attitude towards flooding in the two countries can be summed up in a single world: overload. Here we mean that idea of preparing for something that's nigh on unthinkable. Overload describes a scenario which overloads the protective structures, dams for example.

However, while in this case the water might wreak havoc elsewhere, in Switzerland this exception would be included in the calculated risk. Even in a situation like this, the Swiss are still trying to minimize the damage. On the one hand, for this to work the protective structures cannot be allowed to suddenly fail, if a dam breaks for instance. But on the other hand, the effects can be limited if the alarm is raised in good time and emergency measures are implemented.

 

Can you give an example of an overload situation, and how to deal with it?

In the current floods, the River Mangfall near Rosenheim in Bavaria broke its banks. Yes, a lot has been done since the last major floods, dams were restored, more space has been created for the river, but not all the protective measures were ready in time. Here I'm primarily referring to the polder [low-lying land reclaimed from a body of water and protected by dikes] areas upstream. More major flooding would flood Rosenheim's old town.

The counter-example in Switzerland is the River Reuss in the canton of Uri. Since the major flood in 1987, preparations have been made along the Reuss, anticipating rare but serious incidents. In a really large-scale situation, the water can spill over the dams without breaking them. The water is then diverted into the motorway running parallel to the river. In such a case, the motorway would be blocked off. It changes function to become a drainage channel. The noise barriers are constructed so as to double as flood protection barriers. This lets the river expand without causing large amounts of damage, until it flows into Lake Lucerne.

I do have to point out, however, that neither southern Bavaria nor Switzerland has to cope with rivers on the scale of the Elbe. Rivers this large can only be controlled, if at all, if you consider the drainage basin as a whole and systematically pursue a policy of holistic flood protection, comprising natural reserves, technological measures and flood prevention measures.

 

But if flood prevention fails right at the beginning, what can people further upstream do to protect themselves? Build even bigger dams?

Dams only serve to increase the risk. Flood areas, on the other hand, slow the outflow rate and lower the water level. Havel, at the mouth of the Elbe, offers a good example of these polder areas. The artificial storage spaces downstream on the Havel offer space for around 140 million m³ of water. These areas were flooded only a few days ago, to stop the Elbe floods getting stronger.

If these methods are applied across wide areas, across several federal states, and as early as the upper reaches of the Elbe in the Czech Republic, and farmers are compensated for the use of their agricultural land, you can achieve a great deal. Especially in light of the fact that the flood forecast is better than for many areas in Switzerland, for example. In flatland areas people often know days in advance when the main surge of the flood is going to arrive. In the mountains it's difficult to predict. The situation can change very quickly.

 

Alongside the technological measures, attitudes to flooding also include the actions of individuals. Are the Swiss more aware of the dangers?

I think that in Switzerland there's a more pronounced sense of personal responsibility. People don't just call for the state to come and sort everything out. In Switzerland, people are made aware of natural hazards, with the help of the hazard maps, for example. In extreme cases, in case of overload, people will take their own precautions. It's often possible to protect oneself against flood damage with relatively simple measures. I recently heard about a basement car park where the entrance had been raised by 20 centimeters. This meant that the ramp acts as a sort of barrier, and mobile walls can be added to stop surface water getting in.

In a lot of Swiss cantons [districts], it's also compulsory to have insurance for damage caused by natural hazards. Anyone who has got wet once will think carefully, when looking at the high deductibles, about what they store in their basement.

Michael Grimm

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