It is true that billions of zlotys have been invested in huge investments in flood protection in recent years. But we still see that in some places nature has turned out to be stronger than dams and reservoirs.
– Correct. If in the past it was believed that our technical and engineering thinking was so strong that we could protect ourselves from everything, from any meteorological situation, this way of looking at the risk of flooding has been completely different for many years. We are aware, and I include engineers, that we cannot protect ourselves against all the climatic episodes that we experience.
There have always been floods in rivers. Rivers overflowed their banks, always flooding the floodplains. And this will continue to be the case in the future. Therefore, today the new perspective on flood risk management is that, knowing that we may be subject to these types of threats, we must be better prepared in all aspects other than just the technical one. Of course, we do not give up all the technical infrastructure, that is, maintaining the retention volume that we have. We want to generate new volume, both natural and, in other words, return floodplains and retention areas to the rivers, we want to build new reservoirs, but we are still aware that this will not be enough for all the climatic episodes that will occur.
The fact that such dramas are now happening in places like Kłodzko or Głuchołazy, that is, in places that have suffered a lot before, is it a matter of luck that such heavy rain has fallen in this area again? Is it simply the specificity of this area and its drastic exposure to the elements?
— Of course it is a specific place, because the mountains are a specific place where precipitation is generated. And then there is the current Boris, also specific in his character. And it always happens that mountain rivers generate the most dynamic, most intense, most voluminous flows, and everything happens very quickly.
The second issue, however, is that these rivers have the right and will always have the right to overflow and flood certain areas. And our flooding problems, that is, those related to losses and dangers to human health and life, result mainly from the fact that we live in these valleys. It is a characteristic of the development of human civilization that we embrace rivers, which is a result of our need for water. And that is where we live. And since we live there, we must take into account that we will suffer during extreme weather events. We cannot protect ourselves from everything.
Will the water in places like the center of Kłodzko last for many days? Or maybe it flows quickly, goes further and you can start cleaning quickly?
— In mountainous areas where these flows are faster, where the concentration of this flood wave is faster, this water will also leave these areas more quickly. And the problem will move, in our case, to the north, that is, downstream of our main rivers. Of course, it is necessary to take into account that the rains, even after a pause, will return to the mountainous region. This threatens to create another wave of flooding which, depending on the hydrometeorological situation, could prove equally dangerous.
And this is where Wrocław starts to come into its own.
– Of course. We only have a few days until this wave starts reaching the capital of Lower Silesia. And your hosts will have to face this problem.
A very large city and potentially huge material losses.
— Wrocław is certainly better prepared than it was years ago. The Wrocław waterworks has been modernized and the total capacity of the water supply facilities has been increased. But will it be enough to handle the floods that will occur there? I cannot say that at the moment. Of course, the peak of the wave will be reduced by the retention reservoir in Racibórz, which should be sufficient.
But back to the reality of 1997: will Wrocław absorb such a large wave, and will other cities located in northern Poland, even if they suffer flooding phenomena, be less intense?
– And here we would also have to read the tea leaves. In the cities located north of Wrocław, there are also retention reservoirs that will somehow be able to reduce the flood wave. But to what extent? Hydrological simulations and forecasts are needed to accurately answer this question.
What about Warsaw? We just talked about the dramatically low water level in the Vistula. Could the situation turn the other way and should the capital also be on guard?
— Given the current meteorological situation, I do not believe that there is as great a risk of flooding in the Vistula basin as in the Oder basin.
Will the main factor influencing the near future be when the heavy rains end? Forecasts show that the rains should ease at the beginning of the week.
— If this were to happen and the rainfall lasted relatively less, the peak of the flood wave would also last less.
How much damage can a flood cause? What infrastructure is most exposed to the elements? We hear about bridges being destroyed, for example, in Głuchołazy.
— Many infrastructure elements can be damaged. In Wrocław, for example, the issue of maintaining a sewage treatment plant is important. Such facilities, which would be located in floodplains, could create additional problems and threats related to the deterioration of water quality, which could release pollutants from such a sewage treatment plant. Therefore, this is one of the elements that are very sensitive to flood risk. In addition, bridges, roads, embankments and culverts.
We also have one more element that strongly influences the issue of flood risk: the durability of flood embankments. We have about 8,000 of them in Poland. There are about 8,000 kilometres of them and there is always a potential risk that they will fail under higher loads or longer flooding. This is also something that can – but does not have to – happen. These are particularly difficult things to predict.
We hear from the services that people don’t want to evacuate. They think: we will survive somehow, we don’t want to leave the house. And yet, sometimes, within a few minutes, the situation can deteriorate so drastically that there will be no way or place to escape this deadly trap.
— It is true that although residents are often aware of the risk of flooding, their awareness of the direct threat to life is not always high. Or to put it another way: it often loses out to the willingness to take care of their material well-being. We really do not like to leave our property in such a difficult situation, potentially in the hope of defending our property, which is very dangerous. And this is also an element that has been strongly exposed since 1997 and since 2010. Namely, educating people living in floodplains. Today we hear a lot on TV about taking care of our material well-being, moving valuables to higher floors of our houses and moving cars, agricultural equipment, for example, to places that we know will not be flooded.
Flood risk can be divided into two elements: the possibility of flooding a given area and the issue of losses that will arise as a result of the flooding. If we limit these losses through our various activities, we will only be left with the flooded area, which will then have to be cleaned up, but ultimately our cost of flooding will be lower.
The key is to understand and learn that we must know how to deal with such situations. We cannot rely solely on the Prime Minister to protect us, on the services to protect us, on Polish Waters to protect us. Living in a potentially threatened area, we are also partly responsible for the losses that may occur.
Are we facing a long period of several weeks where our state operates in crisis mode?
– Yes. First, there will be stress related to what happens on other sections of the rivers. Much depends on how long this rainy episode in the south lasts. If it ends soon, most of our critical infrastructure should be able to withstand this single wave. This does not change the fact that we will have to take into account some losses.
Ph.D. Michał Szydłowski is a professor at Gdańsk University of Technology, working at the Department of Geotechnics and Water Engineering.
