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Unwetter: Die unterschätzte Gefahr durch Starkregen | Doku | NDR | 45 Min

Mar 20, 2024
Subtitle: Norddeutscher Rundfunk 2019 Summer 2019. Heavy rain hits northern Germany. One more time. Infrastructure is collapsing in many places. Many people in Lower Saxony still remember the horrific summer of 2017. After days of flooding, several rivers overflowed their banks. That was just two years ago. It was predictable and the community knows what is happening. Experts demand: Municipalities must take many more precautions, for example, renew sewage systems. But many mayors do not address the problem or do so incorrectly. Until now, each municipality has cooked its own soup. Most municipalities are not prepared for the consequences of climate change. What you have to do? *Rolling thunder* Mid-June 2019.
unwetter die untersch tzte gefahr durch starkregen doku ndr 45 min
This summer, storms often break out after a heat wave. Also in the Wolfenbüttel district. Heavy rain falls on two places in the municipality of Elm-Asse. Since the communities are surrounded by fields and fields, the water bodies cause mud flooding. Water penetrates the basement of a school and ruins a renovated workshop. The next day, helpers have to scrape and wash mud from the streets and sidewalks. That's not normal. We don't have large bodies of water nearby. The heavy rain falls punctually in one place. But we can't build a high dam around it so that nothing happens.
unwetter die untersch tzte gefahr durch starkregen doku ndr 45 min

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A few days later. In the town hall of the collective municipality of Elm-Asse. In the construction department, Mathias Stieler and Claus Grothe receive a visit from Mayor Regina Bollmeier. What is Remlingen like? You've already dealt with this and have been able to develop some... ... ideas. Yes, Remlingen was of course a completely different problem: it came from all sides. Otherwise, it is above the aces. In Sandberg... Claus Grothe shows the mayor why the heavy rains caused such enormous damage. Construction department employees have been taking stock for days. A concept is needed so that the municipality can protect itself from the costly consequences of heavy rains.
unwetter die untersch tzte gefahr durch starkregen doku ndr 45 min
That's a strange feeling. You no longer feel safe anywhere. We have a severe weather advisory for today. Everyone looks at the sky worried because no one knows what is coming. On May 20, it already rained heavily in Elm-Asse. That makes two such events in four weeks. Things have gotten worse. I am already an old model and have several years of life experience behind me. There have always been strong and powerful storms. But I really can't remember them being as localized as they are right now. And the frequency is actually increasing extremely rapidly. We are looking at hotspots in Eitzum and Remlingen to get another picture of the place.
unwetter die untersch tzte gefahr durch starkregen doku ndr 45 min
Good. Mathias Stieler and Claus Grothe must develop plans in the common municipality to control the consequences of heavy rain. You already guessed it: it won't be easy. In the summer of 2019, storms flooded northeast and northern Germany several times. In Berlin, sewers and drainage ditches failed. In order to predict the risk of extreme precipitation, meteorologists work with data from German weather stations. You talk about “measuring pots.” The distances between them are relatively large, so not all storms were always recorded. *Rolling thunder* Storm cells are usually small scale. Now studies show what this looks like on radar images.
They have a resolution of 2x2 kilometers. I see more there than with the individual measuring containers. Every storm. In northern Germany, the risk of extreme weather events increases during heavy rain. According to the weather expert, there have been several "southwest places" this summer. They cause an increase in temperatures in the north. We are seeing an increase in southwest locations. With them, the warm air from southwestern Europe reaches us more often. This warm air is warmer than before and absorbs more moisture. He has to get out of the clouds again. Let's look at the radar image: the very dark area causes precipitation of up to 50 liters per square meter in half an hour.
So a lot of water comes out of the clouds. You always have to do with the fact that a countermovement occurs. Skeptics say, "I don't believe that climate change thing." That is why not 100% has shown what is allowed, but 90%. ARD meteorologist Sven Plöger appears on television before the Tagesschau. And at conferences like here at the Ministry of the Environment in Stuttgart. Among the public: many government employees. Plöger's topic: the changes caused by climate change and what federal, state and local governments can do about it. Finally, I talk about Arctic ice and our climate in the future.
Because the Arctic ice is receding... Now we feel the consequences here too. The retreat of ice causes the temperature difference between the equator and the pole to decrease. If it decreases, less compensation is needed. On average, the wind is weaker. This means our ups and downs move more slowly. If they stay longer, the climate is logically more extreme: prolonged maximums, drought and heat in summer. Or a long time under. Like in 2017 against Braunsbach in Württemberg. That's exactly what it's all about: preparing for things like this. And that these heavy rains, when the storms stop, do not distribute the rain, like a broken lawn sprinkler.
A manifestation of climate change. They face the consequences: the two-man team from Elm-Asse's construction department. Your mayor wants to know how citizens and businesses can be protected. On June 11, heavy rain caused a landslide in the fields near Eitzum. To avoid it, they would have to do something here. But there are several problems. Number 1: The state highway maintenance department is responsible for this part. When digging the trench, they must follow different standards than Mathias Stieler and Claus Grothe. This ditch has more volume than the transition to our urban ditch. There we have the traffic jam and the bottleneck.
This means that the diameters of the trenches and pipes do not match. If water enters through the small tube, everything overflows. Next problem: responsibilities. The county road curves back. Responsible: district road maintenance department. Here along the state highway: the road maintenance department of state and federal highways carried out maintenance work. And here, when we reach the urbanized area, it leads through an underground passage into a city irrigation ditch. The city of Schöppenstedt is obliged to maintain it. Within a radius of 150 meters, three different administrations are already involved. Thats not all. Many ditches border private property.
We also need to talk to the residents. Small crossings over the urban ditches lead to many properties. This is obstacle number 3. The problem is the intersections on a property. This represents a narrowing of the stream bed and also greatly reduces flow. It builds up, then overflows and runs onto the property. However, property owners are responsible for crossings. Problem number 4: Before a construction crew can clean the ditches again, residents would have to cut down their trees. This is the situation for both in many places: there are no easy solutions. A few neighborhoods further away, near Hildesheim. Heavy rain devastated the fields in front of the Gronau district of Brüggen.
The masses of mud arrived right in front of Georg Purkhold's house. He is scraping dry mud for the fourth day in a row. Since 2004, his property has flooded several times. What is the logical consequence of this, if it is for so long?: that something has to stop. The church didn't do that. There is only a small overflow left at the exit of the town. That's all. When it starts to rain heavily, and with increasing frequency, situations like this occur. And that was the situation. After the mud flood, firefighters raze the main street. You can only get rid of the sticky dough quickly with lots of water.
Georg Purkhold is alone on his farm. His wife is seriously ill. He sees how the mud dries quickly when it's hot. It was foreseeable what would happen and the community knows what is happening. I think the dear mayor will visit me soon and will have to listen to malicious words. A few days later. He hasn't gone to the mayor, but he is angry. He shows what bothers him so much in the fields above the city. The water that comes from the fields above naturally runs downwards. They have drainage ditches here. When it rains a lot you can see the force with which the water arrives.
All the water should flow through a small tube here and in this direction. The problem is: it is higher there. The water does not rise. As a result, it overflows here and reaches the town. A "mixture of responsibilities" has caused this situation, according to a municipality spokesperson. There was no coordinated planning or maintenance concept with the state and the district. That should change now. This generates anger towards the authorities. But officials can't always do something about it. In the collective municipality of Elm-Asse. Employees of the construction department meet with their mayor in front of the Asse mine.
Here they had relied on a rain retention tank. The rain retention basin remained dry during the recent heavy rains. The rain retention basin remained dry because it fell before the Asse. Bollmeier feels that the heavy rains are increasingly affecting his community. This is already happening, that citizens are contacting me. Because they want to visibly see that something is happening and legitimately. But adapting to climate change costs money. Then I would have to save somewhere else. Actually, I can't do that. We have a very bare house. There is not enough behind or in front. Two highly indebted municipalities have merged.
That is why we have a delay in the renovation of all buildings, in all corners and edges. And we always have to take many measures. Normally we cannot finance anything with any other fund. The community should not go into more debt. Which doesn't make it any easier. Bye bye. Until then. The town of Seesen, on the western edge of the Harz, has much bigger problems. Just two years ago, days of heavy rain caused the flood of the century. The masses of water came from the Harz Mountains and caused the rivers in the lower areas to overflow.
This residential area of ​​Rhüden was also flooded. For days, the Schrader family emptied their house and worked to the point of desperation. Doris Schrader was only able to fix minor problems four days after the flood. Oh darling! There's definitely something there too. Oh good. Are they deformed too? Yes. In his half-timbered house, the broth was a good 40 centimeters high. The ground floor: uninhabitable. My daughter says: move, buy an apartment. But you stick with it, right? Regrettably yes. Awful. The Schraders took on much of the renovation themselves and worked hard for months. Frames, walls, furniture: everything swelled, everything disappeared.
Two years later, the 61-year-old has yet to do so. Black mold has formed behind the tiles due to wet walls. For health reasons he shouldn't do it at all. My cervical spine is no longer cooperating. I know I have to take pills again tonight. Because the pain is sometimes unbearable. They like to walk here to relax: along the Nette. The river near them overflowed at that moment. Thank goodness it didn't keep raining and stop. Just a few days ago it rained a lot. Then they thought I was starting over. (Pedro) The cute one got up... .... and he got up and he got up.
Then he ran over the banks. And then you start shaking and you say: Something is wrong here again. Yes, that is correct. Thoughts of 2017 immediately return. It all came back to me. We walk up and down here. Everyone who asked... ...could not answer, could only cry. Something should have happened a long time ago. The network needs to be deepened and expanded in some places. So that it can drain water better from above. At that time, the water masses of the Harz descended through the Schildau. In order to tame nature in an emergency, the city has wanted to build a rain retention pond since 2007.
The plan: in the event of heavy rains, up to 800,000 cubic meters of water could be dammed. A citizen initiative protested against this. It was unclear then whether the state would help finance the million-dollar project. Environmental impact reports then had to be obtained for all areas of the building, including Nette. You get desperate. At the moment nothing is being done. It only works when the story of environmental sustainability... ...is over. This has to do with approval. Every time you worry: “I hope not again!” Otherwise the water will be very high again. Resentment is also directed against Mayor Erik Homann.
He visited the Schraders in the summer of 2017. So that was the height of the water? No, 35. Thank God we only had 35 x 40 cm of water here. Mr. Homann, what are the chances that anything will change? We have been in the process of containment or dam of Bornhausen for a long time. It could only discourage the couple because the project is very complex. It still is today. The processIt's been going on for a while, in 2018 we had the difficulty of scheduling a discussion. And during this discussion it came to light: The standards for nature conservation and species protection studies had increased.
From the moment we ordered it. That meant we had to get back to nature conservation and species protection. Then the investigations. That's why an environmental planner met one morning in the summer of 2019. Plant scientist and bird expert. List animals and plants in the retention pond area. That's that big group of trees in front. This is this mown meadow. The dam is located, so to speak, behind the meadow. In these areas. And that would be... The Schildau flows behind, in this area. This blue will later become the storage area during floods. And, uh... Walk leisurely over the pond from here and then keep going.
Yes. Yes. Then we look at the interesting points. Some trees would have to be cut down to create the dam. These could be nesting places for rare birds. Therefore, the project could be delayed further. So somewhere... ...the red-backed shrike can be found here in this wet meadow. I have had this on several visits. Maybe it will show. There it sits in the background: the red-backed shrike. It is a fairly small bird, but is known to launch its prey. In fact, it does to some extent. Please? In sloes. Exactly. Or even blackberries. He likes to take grasshoppers or similar small insects and skewer them to eat later.
Each location is noted on maps. They perform these types of inspections several times a year for a complete evaluation by the project manager. The common buzzard spies on voles in the meadows. Plants such as meadowsweet indicate intact wet meadows. Valerian also grows here. And what kind of stork is that? Identification literature is available online. Well, that's why I carry a magnifying glass with me. I can't see it with the naked eye, but I can see it with a magnifying glass. And... ...it looks like it's the Marsh Cranesbill. Whatever fits well in the area. Meteorologists predict more heavy rain.
Flash floods could soon occur again in the Harz Mountains. Lower Saxony had promised flood victims non-bureaucratic aid, with money from the state NBank itself. But Peter Schrader has to continue doing it himself. Only for economic reasons. Because the money we receive from NBank is not enough in either case. There is more damage than the appraiser recorded. He himself could not make the ruler and other more complex things. But companies in the region had long waiting lists. The consequences: the repairs were prolonged and suddenly the Landesbank demanded the return of 11,000 euros. Ongoing problems followed. It's a stupid feeling for me because I usually try to move forward on my own.
Without much help. I would have been better off with a bank loan. I would have paid for my stuff with him and then made the payment in installments. I could have saved myself a lot of trouble and worry... ...The bank granted him a reprieve. Fearing the next flood, biologists have now advanced towards the Schildau stream. Here at the front of the birch you can see that the root plate is exposed. That there is potential for the reproduction of bird species near water. The kingfisher and the dipper come to mind. What they observe could delay construction of the retention basin.
Compensatory areas would have to be found. A red kite flies above them, which probably has its nest here. Definitely used. You can see it on the worn side branch. A red kite is even more important than a red-backed shrike or a common buzzard. This species is endangered and protected. Endangered means it is on a red list. Category 2: critically endangered. At least in Lower Saxony. Sometime in the fall, experts will summarize the results of their inspections. Their report will then be included in the project approval process, which has been underway for six years for construction of the retention basin.
We want all our interests to be taken into account. We want to take into account the protection of species and the conservation of nature. Everyone wants that and this is the result. In this sense, it is not necessary to pass the responsibility to anyone. But you have to live with the fact that these procedures take a long time. Back to the Elm-Asse community hall. We had in Roklum... A major measure is necessary in Roklum. The point is that like a funnel, half the field runs through the town and muddies the street. The municipality of Roklum had a very good idea...
Exactly. Börde is also a lot, but there is... The director of the construction department, Grohte, wants to visit the construction site with employees from all member communities. The goal: identify all weak points during heavy rains. The work would have to be carried out by specialized companies. Then we started talking to our mayors from the member municipalities. These are mainly the ones who bear the costs. The mayor of the municipality has written to her colleagues. He would like to tackle protection against heavy rain together. We have twelve churches. Six accept our offer. Two said: Thank you very much, but we don't have the need.
The other four did not report. This reflects on a small scale what a survey among municipalities shows. “Do you have any concept or policy decision to prevent extreme weather events?” These figures were determined by the German Institute for Urban Studies. Advises federal, state and local governments. Jens Hasse, expert in local adaptation to climate change. Since 2008, the government has been supporting cities and communities to prepare for the consequences of climate change. But that seems to be too much for many local politicians. You can imagine it: a small community, some of which only have 20 to 30 employees. Suddenly they cannot address a problem like a big city municipality or a district administration does.
What really comes out is: the level of knowledge, how do I get data, information, how do I get started, so to speak. That depends a lot on whether someone commits and does it. And in a small community you can convince your mayor. The small community of Kissenbrück belongs to the collective Elm-Asse community. Its honorary mayor is Gerhard Wiche, from the CDU. He was one of those who rejected the mayor's offer to work together to address vulnerabilities in the event of heavy rain. Polsterbrück occupies a special place here. We don't have as much water here as in other communities in Samtgemeinde.
I mean, it's because of the geographic location. Sometimes we get rid of very intense rains. The cushion splashes behind the community center. But when it rains constantly, the stream brings water that flows into the center of the city. "No problem," says Wiche. He had a supermarket built in the flood protection zone. With special permission, slightly elevated and retention basins around it. At Inkissenbrück we are very well prepared for... ...heavy, large-scale rainfall. And here in Pillowbrück we wouldn't have to touch any more money to protect ourselves even more from floods. Two more retention basins would be sufficient in a new development area.
Like him, many local politicians maintain statistically that his area has not been seriously affected so far. This is a very risky consideration if we only focus on its location: "So far it has only affected others." The impulse would be, "Maybe I'll be next." Then, at some point, it affects the community that was saved. The mayor and the head of the building department are using their resources to control the consequences. Future risks must also be taken into account, experts say. As we discovered in the study, we always have the same problems at specific points. We take care of these things.
Not the things where there has never been anything and where there could be something. First of all, we had frequent problems with heavy rain. It is understandable that small municipalities act this way, but that is where the problem lies, according to the expert. The question is always: Have future scenarios been considered? What can happen? There are different statistical methods. This is a different look than the past. In reality, municipalities should conduct “risk assessments” to determine where undetected hazards could arise during heavy rains. These things cost money. This is an engineering job. To do this you need someone who knows how to operate “terrain models”.
Who can bring hydraulic and hydrological models. You have to hire engineering companies for this. This costs money that municipalities often do not have. I also think there is a chain effect. But I am concerned about the slowness and lack of clarity of the decision-making process in federal politics. During his lectures to environment ministers and local politicians, ARD meteorology expert Sven Plöger speaks to many of them. I notice a simple procedure. All the places that have experienced this or have experienced it in their immediate surroundings: they urgently want to do something. Whoever has been lucky enough...
There are many towns in Germany where it has never had much rain because it happened to happen somewhere else. The issue is not so close there. This corresponds to his interrogation. Up to 60% of municipalities do not have any plan in this regard. This is a conclusion that... The federal government has decided since 2008 on a German adaptation strategy. And it runs certain financing programs. Both at the federal level and for municipalities, for years and days. The federal government has to take action on this. Therefore, our recommendations should be directed more towards medium and small municipalities. Mathias Stiehler and Claus Grote from the construction department of the municipality of Elm-Asse could benefit from this.
His analysis also includes agriculture. This shapes much of Lower Saxony. When it rains a lot, sloping fields and fields become a problem. A landslide occurred along this road during the last heavy rains. But they depend on others. As of now, interest in the field is on the way. He is also responsible for the maintenance of the water and the ditch of this ditch. We are in contact with them. On Friday we have an appointment with the nature conservation authority and the field interest group to find out how we will proceed. Then we wait and see. Hmm.
We can't do anything else because it is not our responsibility. The field interest group is the local representation of farmers. Ulrich Löhr from the neighboring town of Groß Denkte speaks for them. He checks the state of the fields on its slopes. He has threshed wheat and wants to plant barley as his next crop. We mix straw and soil to keep the greatest amount of organic matter, straw, on top. So that we prevent erosion and water cannot flow uncontrollably. So that the land stays where it belongs: in the field. As president of the rural town of Braunschweiger Land, he represents the interests of many colleagues in the region.
It has not been plowed here for 20 years because the risk of erosion increases. Instead, like others, he relies on the disc harrow to produce the “compost seeds.” In this way the field would absorb more water. This mulching planting system also involves, to a certain extent, the use of phytosanitary products to eliminate residual weeds. This also includes the professional use of glyphosate for mulching. By “residual weed infestation” he refers to wheat seedlings. The combine does not collect all the grains. The green stalks must disappear before the barley grows. Glyphosate is controversial. In my opinion it is one of the most harmless pesticides.
And one of the best tested. If glyphosate were banned, the plow would inevitably be used. Who turns the soil completely, burying the organic matter. Then there will inevitably be more erosion events. Organic farmers see things differently. Weeds must be cut with the cultivator. That would take more effort, but it is possible. The construction department has another problem. Even if they reached an agreement with all parties involved and suddenly the missing money was there, they still wouldn't be able to dig wider drainage ditches or install larger sewer pipes. They did well. In fact, it is necessary to adjust the calculation bases.
For which event should trenches and pipes be designed? That has changed enormously in recent years. That's how it is. We were waiting for events of a hundred years. Now time is shorter, events happen more frequently. It's not just homeowners who need a different consideration: should downspouts be larger? Also the municipalities. Everyone should consider whether we scale sewer lines differently. The calculation basis comes from flood protection. The fixed point for experts is the “centennial event.” An extreme flood that statistically occurs once every 100 years. Consequently, there are also 50 and 30 year events. Heavier rain means that the previous values ​​are no longer correct.
That's why they are being reviewed. The review of the standardsDIN. Of design sheets. About similar things: in Germany everything is well distributed and there is close collaboration between the administration and the engineering offices. It always takes a few years until all the experts say, "Yeah, that makes sense." Osterholz-Scharmbeck near Bremen. Waiting until new calculation parameters for the sewer pipes were available was impossible for the city. Also in this case the city council ensures that no new debts are incurred. However, municipal public services continue to excavate roads in places considered risk areas for heavy rains. Daniela Rahn from Stadtwerke manages the projects.
At this point she is cutting a path through the industrial zone to replace the sewer pipes. With this measurement on the industrial street, the diameter of the pipes is too small: only 40 centimeters. Now we are expanding the tubes from 40 cm to 70 cm. This allows us to absorb more water, buffer the waterway and drain it into rain retention ponds. The city of Lower Saxony is special. It has not yet been affected by the floods and is still taking action. We don't have to put the child in the well first. drop. It has also rained a lot here, but so far we have been lucky.
In 2013, heavy rain fell on the neighboring community of Hambergen, a few kilometers away. A year later again. This was unimaginable to us and took everyone by surprise. For the mayor of the indebted city, this means that to improve the irrigation system, his treasurer has to save elsewhere. In this way, school common rooms could be designed less elaborately. This is an area of ​​tension. We have to endure individual conflicts. If a major loss occurs because we didn't take precautions, we have completely different problems. That's why I can easily argue that we invest money in something that cannot be seen.
As coffers are tight, municipal services can only spend 400,000 euros a year on this. That's why not as many new pipes can be installed. Preventing flooding from rain becomes a race against time. The specialist has to adapt. I would have liked to rebuild an entire street, that is, install a new stormwater drain there. But there are not enough resources for that. Then I have to share the construction project. I have to do two tenders and plan these sections so that the budget is sufficient. The race against time. Now it's a marathon in Seesen. The city has wanted to build a rainwater retention basin for twelve years, but there have been protests from residents and the dangers of nature conservation.
And always finances. The small town alone can barely raise 13 million euros. Until now, each municipality has cooked its own soup. Each municipality is responsible for flood protection. But you can't see this locally, only on a large scale. Then flood protection makes sense and is effective. This idea brings the solution. Seesen belongs to the Goslar district. Together with the district of Hildesheim, the city of Hildesheim and the city of Salzgitter, they form the “Innerste Flood Association”. Because the rivers do not stop at the municipal limits. The association is financed by the state of Lower Saxony with a special fund of 27 million euros per year.
Seesen also benefits from this when constructing the holding tank. This means that once we have the planning approval decision, we will hand over this project to this newly founded association. He builds and operates the pool. This is much better for us financially because the burden is spread across many shoulders. Because if there is no construction above, the communities below will always get their feet wet. These types of collaborations are still very rare. Almost 75% of the municipalities surveyed cannot or do not want to work with their neighbors. Cross-border collaboration offers many advantages. Shared costs for research and construction projects, for example.
I think that... ... it is also clear to the citizens, the taxpayers: here we cooperate so that we all benefit. These are advantages where, of course, two people always have to share the photo, which is what is ultimately created. There are solutions for overwhelmed municipalities. Federal and state governments would have to fund flood protection more and more effectively. And those responsible for the communities work more together. They can hardly cope alone with the consequences of heavy rains. Copyright Subtitles: NDR 2019

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