Banedanmark's new sensors keep an eye on known beaver and extreme weather

A beaver has become nationally known for building a dam at a passage under the railway between Herning and Struer, and thus causing train delays. Heavy rain causes the water level to rise, the path of the water changes, and if the beaver's dam becomes too high, the risk of undermining the railway increases.

Today, Banedanmark can follow developments in real time. New sensors measure the water level both before and after the flow, and when the levels become critical, the emergency services can react in time. In practice, this means that Banedanmark, in collaboration with the municipality, continuously ensures that the beaver dam is partially removed so that the water can continue to pass through. 

The sensors make it possible to follow how the water level reacts when the dam is changed, and experience has shown that the beaver quickly builds on again.

"We can see that the beaver is often particularly active after we have been out removing some of the dam. I can't help but feel a little sorry for it, but we are not allowed to move it, as it is protected, and so it is smart that our meter can tell us when the dam gets too big," says Lene Bøgebjerg Bøgvad, climate adaptation manager at Banedanmark.

Kibæk incident was a turning point

The beaver is just one example of why Banedanmark is currently rolling out a nationwide system of sensors along the railway. The work was started in earnest after the dam breach at Kibæk in West Jutland in 2022, when heavy rain undermined the railway embankment and train traffic had to be suspended for several weeks.

Subsequently, Banedanmark launched a risk assessment of the railway's most vulnerable sections. The preliminary results from 2024 and 2025 are already being used to prioritise where the sensors will be installed, although the overall risk assessment is still ongoing.

"The assessment showed that many of our passages, pipes and drains under the railway were designed 100 to 200 years ago, and therefore cannot keep up with the amount of rain we see today. At the same time, we do not have unimaginable funds to rebuild all over Denmark at once, and therefore we prepared a contingency plan and decided to set up sensors," says Lene Bøgebjerg Bøgvad.

Sensors as early warnings

Banedanmark is therefore in the process of installing up to 1,200 sensors along the railway throughout the country. A decision that was made in 2023: 200-300 sensors have already been installed, and the rest will be rolled out during 2026.

The sensors act as early warnings and monitor water levels at flows, drains and bridges.

"When we see that the water level is developing in the wrong direction, we can send out the emergency services and keep the flow free. Many of the incidents we avert never become news, precisely because we manage to react in time," she says.

Another example is the Greve brook on Zealand, where a submerged watercourse under the railway is regularly blocked by garbage, bicycles and other foreign objects. Here, the sensors make it possible to intervene before the area becomes impassable.

Water measurements are shared because water knows no boundaries

A central part of Banedanmark's approach is that data from the sensors is shared openly. Data is collected via VandaHydro and made freely available via the joint public platform Kemidata, which is operated by Danmarks Miljøportal.

"Water does not stop at municipal borders. If the water level is abnormally high in one place, it can have consequences further down in the system. That's why the municipalities often call us to see if our meters can tell them anything, and that's why we share our measurements so that everyone can benefit from them," says Lene Bøgebjerg Bøgvad.

Several municipalities already use Banedanmark's data, just as Banedanmark itself draws on municipal measurements. Research institutions have also shown interest, for example in data on near-ground groundwater and smaller streams, which are otherwise rarely monitored systematically.

More knowledge leads to a more robust railway

According to Banedanmark, the sensors have already provided new knowledge about the plants' vulnerability and unexpected bottlenecks.

"A small pipe of 30 centimeters can be just as critical as a large flow. The sensors give us a completely new understanding of our facilities and a better basis for prioritizing efforts," says Lene Bøgebjerg Bøgvad.

With real-time monitoring, strengthened preparedness and open data sharing, Banedanmark is working to make the railway more robust in a climate where both extreme weather and nature's own actors play an increasingly important role.

Banedanmark's water measurements are freely available to everyone together with other water measurements on kemidata.miljoeportal.dk (search "Continuous measurements" on the left and select "hydrometry" as the study type), and are shared in collaboration with several operators, including Watson C, WSP, Kollektio, Klimator, HydroInform and SpectroFly.