Building in the low-lying Rijnenburg polder, whether or not to do it? – Area development.nu

On 17 May 2022, Minister Hugo de Jonge (Public Housing and Spatial Planning) wrote in the new Spatial Planning Letter that water and soil must become more guiding for spatial plans. This means that we look closely at the soil and water structure when building assignments. Is an area low? Does it have a soft peat soil? Or, is it naturally wet and soggy? This will require spatial adjustments and additional measures.

The water boards have knowledge of soil and water and are happy to play a role in the (housing) construction task. Haan: “If you want to make water and soil truly steerable, early involvement of water boards is crucial. Not regulating afterwards, but co-creating at the front. Choices we make now have consequences for the future. So let’s make soil and climate-proof building, so that new homes are prepared for the changing climate.”

Polder Rijnenburg in Utrecht

The Rijnenburg polder in the Utrecht region is a large piece of land between IJsselstein, De Meern (Utrecht) and Nieuwegein. At first glance, it looks like an ideal building location: close to the city, nearby highways and plenty of space for homes. Reality shows that it is a lot more complex. Climate change is increasingly causing extreme weather: long periods of drought and heavy downpours.

The extreme precipitation of Limburg in 2021 could also fall in Utrecht. Low-lying polders will then unmistakably be affected by flooding. Jeroen Haan: “As a water board, we have looked at what the amount of precipitation, such as in Limburg, means for our area. This will also lead to significant flooding in the Utrecht region. If we zoom in on Rijnenburg, we see that a large part of the polder comes under water. Then you have to think carefully about whether you want to build there and if so, how.”

Concept study: 3 variants

Earlier this year, the municipality of Utrecht presented a concept study into the possibilities for the polder. Three variants were presented in it: an energy landscape, small Rijnenburg (20,000 homes) and large Rijnenburg (40,000 homes). Water Board De Stichtse Rijnlanden was clear about possible housing plans: ‘no, unless’.

In concrete terms: the water board would rather see no construction here, but if there really is no other option, then soil and climate-proof. The variant great Rijnenburg is therefore not an option for the water board. And small Rijnenburg then? Haan: “Building in the polder entails great risks. At the same time, we understand that the housing shortage is high. That is why we are now looking at further elaborations of the concept study together with the municipality of Utrecht. and soil guiding in the spatial planning. What is needed to be able to live here in a future-proof way, if there are homes anyway?”

Climate proof is the new normal

The dike warden continues: “Extreme precipitation and extreme drought, the past summers clearly show that the climate is changing. In addition, high water in the rivers is more common. We can speak of a climate crisis.

That is why we now have to think very carefully which function we place where. Are you building in a polder that is low and that should actually serve as water storage? In Zuidplas and Westergouwe, the plans are already further along than in our region. There you see that it is possible, but that it is not easy.

The adjustments that you have to make in such places in order to continue living there in the future are large. But we can’t do otherwise. Climate-proof building must be the new normal. Making climate-proof choices now prevents a potential loss of billions of euros in the future. Invest up front and avoid repair afterwards.”

Change of mindset

We used to read the landscape: construction was mainly done on the higher ridges. If a location was not suitable, we looked for other places. But large-scale urbanization has meant that the role of the landscape has faded more into the background. Water and greenery have social value and are indispensable for quality of life, biodiversity, nature development and recreation. But they are not always valued as such in traditional land development.

In fact, water and green are seen as costs rather than benefits. That has to change. If we really want to make water and soil directing, then we have to realize that the value of this is enormous. There is a role for the government, developers, insurers and the financial sector. The first steps in this direction are already being taken. For example, banks are conducting climate stress tests and there are plans to make lending more expensive in locations that are more risky due to climate change.

Innovations needed

But with only a change of mindset we’re not there. Jeroen Haan: “As a water board, we stimulate innovative research into new, more flexible forms of housing. For example, together with the municipality of Utrecht, we are participating in a study into floating construction in Rijnenburg. Traditional construction may be cheaper up front, but will lead to better results in the long run. climate-sensitive construction sites to more maintenance and damage.

Land subsidence, flooding, we have to deal with them more and more often and faster. Then it is better to invest now in innovative forms of living that in the long run will result in much less maintenance and damage. Together with local authorities, we make agreements about climate-proof construction. For example, there is a ‘Climate Adaptive Building Covenant’ in the province of Utrecht. Goal? Reducing flooding, heat stress, drought and subsidence and increasing biodiversity.”

From water key to water port

There are plenty of ideas and plans, but the question is how to put them into practice. An instrument that should help with this is the water test, introduced in 2003. The idea behind this is to involve water boards in spatial projects as early as possible. In many cases this is already going well, but it could be even better.

The new Environment Act changes the water test into the weighing the importance of water. Municipalities must therefore take the views of the water manager into account when establishing the environmental plan. Dijkgraaf Haan: “We have to move from a water test to a water gate. Not first develop plans and then test, but first through the water gate for climate-proof construction and then further develop it. bring in knowledge and expertise and together we develop future-proof neighbourhoods.”

Good cooperation with the municipality of Utrecht

And fortunately that happens regularly in practice. Hoogheemraadschap De Stichtse Rijnlanden and the municipality of Utrecht work well together in the field of climate-proof construction. Good examples of this are Leidsche Rijn and the development of the Merwede district. Leidsche Rijn started in the 1990s and about 90% of the homes have now been built.

In this district you will see a lot of greenery, large ponds and wadis. These wadis ensure that rainwater from the roofs and roads infiltrates into the soil. And in the development of the Merwede district, climate-adaptive construction is also taking place. Building blocks are designed in such a way that extreme rain showers once every 100 years cause no damage. In concrete terms: the requirement is that a shower of 80 mm per hour can be processed. For example, through water storage or drainage to surface water. It should become a matter of course that the water board sits down at the table early to work together on a future-proof, liveable area.

So, building in the Rijnenburg polder?

The good examples are there and climate-adaptive building is slowly gaining a foothold. Haan: “The extreme summers of recent years, with periods of severe drought and flooding, have opened the eyes of a large public. Climate change is serious and we are already dealing with it. That insight is certainly also included in plans for spatial developments.”

Does that mean that building in the Rijnenburg polder is okay, provided that it is climate-proof? “The question remains whether building in low-lying polders is really sensible. But ultimately, as a water board, we also feel responsible for the range of social tasks that must be given a place somewhere and we also see the enormous housing shortage in the region. together with the municipality of Utrecht, we explore the possibilities. From advising to co-creating and introducing more upstream water and climate interests. – and climate proof and we don’t burden future generations with the risks and the price tag.”