Building with nature

During an interview with Henk Hartzema, it quickly became clear that this is not a simple urban planning undertaking. It is a project that show the way in which the Netherlands wants to live with nature that is becoming less and less predictable. It is about creating symbiosis landscapes in which different spatial processes work together.

The birth of Stad aan het Sloe

For about five years I have been working on the Southwestern Delta, everything that binds the provinces of Zeeland, South Holland and West Brabant, as an area, where land and sea meet. In 2022, Deltares and TU Delft submitted a call for a research by design study within the catchment area of the major rivers, Redesigning Deltas. Within this, we investigated the Southwestern Delta, departing from a sea level rise of about three meters. This has led to a long-term project called Zeelandia.

I find the area so fascinating because nowhere does it become as tangible that we as humans are fighting against the elements, as here. We found out that we are looking for connections between all kinds of processes, which are key. We have called these symbiosis landscapes.

Where you can still see that you have nature, a dike, a village, a business park or a recreation park, it would be much nicer and better if those things reinforce each other. That a kind of ecosystems are created in which different users, species and target groups can find each other. For some people this is difficult to imagine and that is why we have proposed City to the Sloe.

With this concept, people usually immediately understand what I mean. For me, that is a landscape that is in its purest, complete form. In which accessibility, human habitation, nature, safety and livelihood security come together.

The city is ultimately the symbol of man who settles on earth and constantly has to deal with the elements around him. Sometimes against it, sometimes with it, but always in cooperation. So that’s how Stad aan het Sloe came to light, about two and a half years ago.

Working with sea level rise, salinization and flood risks

Within Zeelandia, we have developed three scenarios for the entire Southwest Delta. These are the characteristic scenarios as drawn up by Deltares: moving along, holding back (raising dikes) or seaward. In all cases, something is really going to change. What many people don’t know, including me before I delved into Zeeland, is that less than ten percent of all river water flows into the sea via Zeeland. About eighty percent goes via the port of Rotterdam, the rest via the river IJssel.

If the sea level really starts to rise, you have to put Rotterdam behind the locks, just like Amsterdam is now. This means that eighty to ninety percent of the river water has only one way out: through Zeeland. There is no alternative: northern routes such as those used to exist at Katwijk no longer exist, and the IJsselmeer and the Afsluitdijk can only handle a limited amount of water. At the same time, we know that our rivers are increasingly becoming rainwater rivers, with lower valleys and higher peaks. All that extra water must therefore flow through Zeeland. The province is not ready for that at all, because we have dammed and closed everything there. So it would all have to open again.

The real mobility scenario means that the sea would come back into the land, with an elevation of three meters it will come as far as Gorinchem, halfway the Netherlands. We have to make the river dikes enormously higher and make the catchment area of the rivers wider. This will create a kind of mudflat landscape right through our country and in which the rivers can flow in and out.

In this scenario, a large part of Zeeland becomes unsuitable for permanent residence or agriculture. It is lost to use as we know it today. Certain parts can be secured behind dikes, such as the southern part of Zeeland, where Stad aan het Sloe is located. Habitation would then move from the middle of Zeeland to the south, because that area can be better protected against sea level rise.

In addition, many dammed waters, such as the Veerse Meer, the Grevelingen and the Haringvliet, are ecologically almost dead. Biodiversity is collapsing. So we have to allow currents and perhaps ebb and flow there again to make it livable again.

Interdisciplinary collaboration

The Zeelandia team consists of urban planners and we work together with LOF landscape architects and engineering firm Witteveen+Bos. So we really brought together with three disciplines, because it is an incredible puzzle in which all the lines are intertwined. As urban planners, you are of course concerned with the quality of the environment, but a landscape architect and an engineer who understand exactly how water works. They are concerned with how salinization occurs and how you can stop it, this is really indispensable.

When the sea comes

A possible public relocation as a result of climate change is something very big. Social security is important, but we cannot control everything. We don’t know exactly when the sea level will rise three meters, if at all. In addition, as a designer, we are of course not in charge of the political decisions that are made. What the research has mainly brought us is the realization that sometimes you have to go all the way. We have recognized that you don’t have to give up fighting against the elements, but actually have to move along more.

If the delta widens and people eventually have to leave their homes, you can’t just start shouting that. This creates social unrest and economic problems. You can show that there are natural processes that you sometimes have to give in to. I think we are slowly realizing that the modernist era of being able to control everything is over. Nature shows its muscles, and then you notice that we can’t control everything. Eventually, hopefully, the realization will grow that we are only a small part of something bigger.

The impact of building on nature

I think that the impact of building on nature will be minimal. In any case, the area in which we are going to build is currently agricultural land. In it, the work starts with making a landscape in which the creeks are opened up again. As a result, we immediately increase biodiversity. Because yes, agriculture looks very green, but ecologically it is not optimal. In Zeeland this is even worse because we are dealing with enormous salinization.

Fresh water is constantly thrown on there, but that only pushes the salt water down temporarily. Furthermore, we also drive the soil completely closed with huge agricultural vehicles. We are really flattening it and impoverishing it. Every week, about 150 tankers already drive from the basin Grevelingen, filling up with fresh water and taking it to the Bevelanden Islands to scatter over the fields. This is of course very artificial and finite.

The creeks restored to their former glory

We are going to dig out those creeks, but without ebb and flow they are no longer real creeks. You get artificial watercourses with overgrowth around them. Rewilding then means that we give some of it back to nature, although that can never happen all by itself, because then things happen that you don’t want. So we have to investigate which nature suits water that mainly has to retain rainwater. Because against salinization, buffering is the most important thing: not getting rid of rainwater. As a result, those creeks become water reserves, with fluctuating water levels that we have to engineer carefully.

Living with nature also in other places in the Netherlands

The conclusion of the Zeelandia design research is that we need to live more with nature, in whatever way we can. Whether that means being more aware of it, being more in touch with it, becoming part of nature or reacting to it. It’s about designing viable environments. The location for Stad aan het Sloe was chosen because it is an intersection of two important preconditions: it must be above sea level and it must be easily accessible by public transport. We scanned the map and this place came out. Strangely enough, everyone thinks of Zeeland as the lowest part of the Netherlands, but there are also parts near the 50% highest parts and we are exactly on that.
Building above sea level seems to me to be the absolute minimum for future developments. Not building below sea level is a matter of common sense. Accessibility, water safety and nature value are our criteria. You can also apply this to new cities or expansions. Living with nature is the starting point of symbiosis landscapes.