Climate adaptation: what do we need and what risks do we accept?

The Netherlands wants to be climate-proof by 2050. But when are you climate-proof? You can't prevent everything. What performance must our network deliver, at what cost and what risks do we accept? As Rijkswaterstaat we are working with the Ministry to make these considerations. So that we take the right measures and limit the damage during flooding and flooding, but also during severe drought and extreme heat. And so make our networks climate-proof.

In this section I focus on the 'wet' networks of Rijkswaterstaat, or in other words: what does climate adaptation mean for the main water system and main waterway network? It is often about damage to objects due to weather extremes, but climate change also has an impact on maintenance windows, for example. We can only maintain a storm surge barrier when the water level is low, but rising sea levels and storms mean that this level is being exceeded more and more often. We have to deal with that, because maintenance is crucial for the functioning of the barrier. And in the summer of 2021 we saw in Limburg that high water levels no longer occur only in winter. If you are then just doing regular maintenance on a weir, as usual in the summer, you do have a challenge.

In the southern Netherlands we are now preparing to renew the 100-year-old weirs in the Meuse. The seven weirs in the Meuse at Borgharen, Linne, Roermond, Belfeld, Sambeek, Grave and Lith form one system. Between 2028 and 2035 they will reach the end of their technical lifespan. Climate adaptation plays a very large role in choosing the right solution. If we are going to replace them, we actually have to look 100 years ahead. That offers opportunities to prepare for the future. With renovation, we look 30 years ahead. That may seem to offer fewer opportunities, but it can also be a wise choice. After all, the new KNMI scenarios still have uncertainties and variables. And how far can we limit global emissions and thus the rise in temperature? We don't know exactly where it will go. We will have more insights in 30 years. But we also know that we already have frequent problems in dry times with low river discharges. In that, the Meuse is becoming increasingly vulnerable. We are now in the middle of deciding whether to replace or renovate. 

Rijkswaterstaat also conducts periodic stress tests on its network, as do all governments. We then map out the vulnerable spots. On the Brabant canals, for example, the junction of the Zuid-Willemsvaart with the Wilhelmina Canal proved to be a vulnerable point. During extreme rainfall, the volume of water draining from two water boards may exceed the amount we can discharge. This stretch of 40 kilometers in length is also called the rain barrel of Brabant. Not only do we collect water here, but we also use it in dry times.

Last winter we saw how crucial it is to think about climate adaptation and redundancy, because "in the rain barrel," the valve of a sluice gate at Lock IV jammed. The system here is set up in such a way with a lock chamber for navigation and, in addition, a sluice chamber for controlling the water level on the canal. In order to still be able to regulate the water level when the sluice chamber became jammed, the lock chamber doors were opened to discharge right through the lock chamber. Unfortunately, this meant that navigation came to a standstill, but it did mean that a considerable part of the surrounding area kept its feet dry. 

We are currently investigating in what climate-adaptive way we can increase the drainage capacity of this 'rain barrel'. We have linked this to the Flood Approach Brabant East program, initiated to protect the environment in the Den Bosch region from high water. We are working together with the water boards to find a solution. But I also link the results back to policy. What performance do we want to deliver, at what cost, and what risks do we accept? 

The Pen - Carina Verbeek – Climate adaptation consultant at Rijkswaterstaat Zuid-Nederland.