UPWr Experts – flooding in Poland

Reservoirs will reduce flood waves, but rivers will still overflow

Water has once again shown how dangerous a force it can be, and once again, in many places, we have lost the battle against high waters. Professor, is it possible to fight floods effectively?

We must try. There are several measures we can take to minimize losses. First and foremost, we need to efficiently operate flood control infrastructure and build water reservoirs—both retention reservoirs, which store water, and dry reservoirs, which hold water during flood surges. Well-managed retention reservoirs reduce flood waves and often prevent large-scale flooding. Similarly, dry flood control reservoirs are important.

However, we must remember that water reservoirs with flood control functions are only effective to a certain degree, typically between 30 and 60 percent, although it's hard to estimate precisely. But without reservoirs, especially new ones like the Racibórz Reservoir on the Oder River, built after 1997, the situation in Wrocław could be worse than what we witnessed 27 years ago.

Proper management of water levels is also crucial. Moreover, water infrastructure alone is not enough; well-trained personnel are just as important. That’s why we should focus on acquiring specialized knowledge and educating experts, as we do at the Wrocław University of Environmental and Life Sciences in fields like water engineering, environmental engineering, and the new discipline of climate change adaptation.

It is essential to understand that flood management must be based on catchment area management. What happens upstream from Wrocław—in places like Racibórz, Kędzierzyn-Koźle, Krapkowice, Opole, and Brzeg—has a significant impact on Wrocław and beyond.

We must also remember that it is us who have developed floodplain areas where we live, areas where rivers have naturally overflowed for centuries.

That doesn't sound very optimistic.

No, because water management must take into account the full spectrum of interconnected factors—from flood protection to maintaining drainage ditches. We cannot develop these areas or neglect their maintenance without consequences. Water management planning requires flexibility, so that we are prepared for various scenarios and, when investing, can implement the most effective solutions. We should also build floodplains where possible, areas that can flood in case of emergencies. Let’s not say that hydraulic engineering solutions only exacerbate the problem. Fortunately, many teams of hydrologists, hydraulic engineers, biologists, ecologists, and economists are conducting research that can successfully be applied by those interested in sustainable water management.

What can each of us do to help reduce potential flood damage?

There are many actions we can take: proper rainwater drainage around the house, maintaining functional drainage ditches, securing sewer systems to prevent backflow, and preparing homes for floods (using permanent barriers, sandbags, or preparing family evacuation plans).

Rivers should have space to spread during floods

Dr. Sebastian Szklarek from the European Regional Centre for Ecohydrology of the Polish Academy of Sciences stated that water has a memory and returns to its old paths. However, our memory seems short. We keep making the same mistakes and fail to learn enough from them...

For centuries, we have tried to tame rivers by regulating their courses, shortening their paths, and cutting them off from floodplains with levees. The scale of the 1997 flood and the one this year clearly show that we cannot win this battle. So instead of fighting, we should start cooperating with rivers—holistically and comprehensively. Right now, we’re mostly talking about the risks and effects of flooding, as if we’ve forgotten the ongoing drought affecting much of the country, particularly in the north and east. Therefore, we must create solutions that mitigate both threats while simultaneously improving water quality and protecting biodiversity. This is often possible and achievable, but we need to change our approach and mindset. Politicians and decision-makers must also understand this. We need to find financial resources, launch programs, and implement them widely. We, as a university, are ready to educate a new generation of experts who will face the challenging task of managing water resources in the coming decades.

In this context, there is increasing talk about relocating floodplain communities. We can’t move places like Kłodzko, but what about small towns?

When we talk about giving rivers space to spread across valleys during floods—and such events will inevitably occur more frequently and on a scale we cannot yet predict—we must consider the most radical actions. This includes relocating the most flood-prone parts of or even entire towns. These measures may prove to be more rational economically, socially, and logistically than continuously investing in ineffective technical flood protection and rebuilding after disasters. People and animals are dying—losses that are difficult to even quantify. The problem is growing rapidly, and insurance companies are noticing, refusing to take on the risk. People are losing their entire livelihoods overnight. Then, a few years later, they forget, local authorities entice investors, someone buys a cheap plot of land, builds a house—and the cycle repeats. This vicious circle needs to be broken. Land management practices must change because ignoring the consequences of these mistakes is becoming too costly.

How do you assess the management of flood control infrastructure? This issue has raised many questions and doubts in recent days.

Yes, and that’s despite the fact that the management is undoubtedly being carried out in accordance with pre-developed operational instructions. However, the scale and dynamics of the current flood events show that these methods need to be improved. In my opinion, the biggest issue was the failure to respond to the predicted rainfall in time. For example, the reservoirs of the Nysa cascade should have been emptied much earlier, at a pace that was safe for the towns located downstream. At its peak, the discharge reached 1500 m³/s, causing widespread flooding in the Nysa Kłodzka valley and increasing the risk of a larger flood wave on the Oder. Fortunately, the Racibórz reservoir performed its function well, sparing downstream towns, including Wrocław, from the scale of flooding seen in 1997.

What about deforestation? Did it contribute to the dramatic situation in the Kłodzko Basin?

Mountain forests should primarily serve water retention and soil protection purposes. Economic use should not be the priority. Unfortunately, this is not the case. When combined with the widespread die-off of coniferous forests following the 2015 drought, we have a significant problem. Additionally, the scale and methods of timber harvesting—massive machines that damage the soil, create deep ruts, and the expansion of forest roads—all contribute to significant adverse hydrological changes in mountain watersheds over the past decades. This includes the effective slowing of runoff into lower areas and watercourses.

During this year's flood, we also heard about outdated infrastructure that couldn’t withstand the massive volume of water. It seems there is much to improve here as well.

That’s true. And there will undoubtedly be enormous public pressure, and likely political will, to build a series of new retention reservoirs, deepen riverbeds, and raise levees. Some of these investments are rational and necessary. However, the current events show that we are struggling to maintain the technical condition and proper functioning of the existing infrastructure. This results from various factors: years of underfunding in the water sector, increasing staff shortages, and organizational and political issues—water is managed by three different ministries. We need to approach these issues more broadly, optimizing the management of entire watersheds. First, we need to promote widespread landscape retention in agricultural and forested areas, provide rivers with adequate space in their valleys, restore natural retention in wetlands. Only then should we consider supplementing this natural retention system with artificial reservoirs and other technical infrastructure.

Measuring flows to more acurately model future flood waves

Employees of the Institute of Environmental Engineering at UPWr have been conducting unique research on the Oder River since yesterday. They are measuring the river's flow at the entrance to the Wrocław Water Junction, in the areas of the Opatowice and Bartoszowice weirs.

These studies are crucial for determining the distribution of water flowing through Wrocław, specifically at the bifurcation in Biskupin, where the river splits into the Oder and navigational canals. This is the first time such research has been conducted during a major flood surge, and it is essential for establishing points on the flow curve. In the future, this will help to precisely model how flood waves pass through the city.

These studies would not have been possible without the assistance of the WOPR (Water Volunteer Rescue Service), police, fire brigade, and the company Water Survey Tech.
 

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  UPWr Experts – intense yet short rainfall doesn't solve the problem of droughts

  Prof. Ewa Burszta-Adamiak from the Institute of Environmental Engineering at UPWr discusses flash floods caused by short and intense rainfall, which bring more harm than benefits to the environment, water retention, and our habits that, surprisingly, can make a significant difference.