Climate and monuments

The heavy rainfall, the increasingly violent storms and the fluctuating temperatures. All these climate changes have a major impact on our living environment. Monuments are increasingly at risk of being damaged by, for example, extreme hailstorms or falling trees. What are the consequences of the climate for heritage?

In the process, Monument Ownership also faces new challenges around climate change. How do you deal with them? We share some scenarios we have experience with.

Nuisance due to rain

None of our monuments is in a flood-prone area. Nevertheless, we have experienced extreme rainfall on a number of occasions. "In some cases, water can naturally subside, as happened for example recently at the Ruïne van Brederode when the bridge there was flooded due to heavy rainfall. But in other cases you really have to take action yourself," says project manager Robin Koot.

This was the case at Radboud Castle last year. When a number of locks in the Afsluitdijk did not work and there was flooding due to heavy rainfall at the same time, water entered certain areas. Together with the fire brigade, the water was then drained to the IJsselmeer. Fortunately, there was hardly any damage to the interior.

Adapting buildings

Our colleagues who work daily to maintain monuments always look at water. How is it drained? What does the roof surface look like? With a small surface there is often less water flooding. Where necessary, we modify the monument without affecting its appearance. This is increasingly necessary due to changing conditions. "For example, at the Grote Kerk Veere we have increased the drainage capacity of the rainwater discharge by installing an additional drain because of the increase in regular rainfall. In addition, we have increased the diameters of the clean water sewer so that there is more capacity to drain water quickly."

What we have started doing differently due to the increase in rainfall is that we have gutters and rainwater drainage checked and cleaned more often. We include this as standard in the annual maintenance for the monument, but it now has to be done more often than before. Where that used to be once a year, for example, it is now twice or more.

Green management

Not only do you spend more time repairing weather damage when maintaining the building, more time is also spent restoring the greenery. "Storms in the past have sometimes given damage to the greenery around our monuments," says director-director Mark van den Bos. "More and more often we get a report of a fallen tree after a storm has blown around, like last year at the Ruins of Teylingen. You get to deal with that more and more often now. So we are freeing up more budget for replanting the greenery around the monuments. In management and maintenance you may also have to intervene earlier or more often than before, such as pruning the trees at more frequent intervals. So it involves an adjustment in the strategy of green management and more alertness." Planting trees, plants or other crops does not happen overnight. We do it based on a green plan. Mark: "We always keep looking at the historical layout and based on that you make a plan for the greenery."

In the restoration of Buitenplaats Trompenburgh, greenery also plays an important role. The existing green structure will be adapted, according to the design of landscape architects Karres+Brands, and reconstructed according to a ^17th-century design. Robin: "We are going to plant 345 new trees for this. When planting the new garden, we choose plants that resist heat well and require little water during certain periods. For example, we are not planting oak trees but lime trees, because they are stronger and hold up better in more difficult climates."

Heat problems

Against the amount of rain, longer periods of drought are becoming more frequent. This is also causing more and more problems, Robin says. "About 2 or 3 years ago the whole moat was dry at Slangenburg Castle. Then I had to rush there in the evening to rescue as many of the carp as possible together with the animal ambulance."

One challenge around heat that we face is also related to water. If it has been dry for an extended period of time and then a lot of rain falls in a short period of time. Then the water cannot infiltrate into the ground. The soil remains boggy and recreation breaks it up. In dry periods, erosion from treading is also a danger to the greenery. Nature does not get a chance to recover when many people walk on it. "We therefore made a plan at the Naarden Vesting for where we do allow people and where we don't. So as to give nature more room for recovery," says director-director Mark.

By alternating dry and wet periods there is also a greater chance of grass growing between the stones, as happened at the Burcht van Oostvoorne. These plants cause damage to the monument, so they have to be removed.

Direct and indirect consequences

"In previous winter periods, the basement of Slangenburg Castle was also flooded. Then, too, we had to pump away," adds managing director Mark van den Bos. "These are direct consequences of climate change that we are already noticing and have to anticipate. But you also have indirect consequences..."

It may sound crazy, but for monuments, a high water table is actually pleasant. Mark explains further. "If the wooden pile foundation under the building is under water then you don't get rotten piles. Once your pile heads get above water, oxygen gets to them and they start to rot. We hear that more and more that that happens in the heritage sector. Fortunately, we haven't had a problem with that yet!"