The sea level is rising and the Netherlands continues to build in the polder

In our summer clothes, we enjoy the good weather until November. New Year’s Eve was hotter than ever. The climate summit in Egypt showed that there is a huge gap between promised and required CO2 emission reductions. This means agreements to limit global warming to 1.5 degrees Celsius seem even further away. So the world really needs to take into account further sea level rise.

Villages are displaced in Fiji. Indonesia is even going to build a whole new capital. And what is the Netherlands doing? We are going to build new houses in the deepest polder. The following arguments are used in the Master Plan Middengebied Zuidplaspolder: in the event of a dike breach, you have up to 32 hours to escape and the houses are built high up in the (deepest) polder so that a level of high groundwater can be properly absorbed. Other arguments heard in favor of building in the polder are that a large part of the Netherlands is below the NAP and that farming in the polder is not sustainable because it requires a lowering of the level of groundwater (and thus accelerates subsidence).

With climate change, saline infiltration will also increase and surface water storage must be considered, both to bridge dry periods and to absorb extreme rainfall. The deep polders of the Netherlands seem the most suitable for this.

Adapting to the climate is now at the top of the ambitions of municipalities in the development of new living and working spaces. In this case, it is mainly a question of limiting the thermal stress linked to global warming and retaining rainwater longer to limit the consequences of more extreme climatic conditions. Good initiatives, but is it enough?

The national government is concerned about the height of the dykes. Deltares research commissioned by the Department of I&W (“Strategies for Adapting to High and Accelerating Sea Level Rise, An Exploration” September 2019) has clearly shown that current sea defenses cannot be raised indefinitely. Four strategies are now considered when thinking about solutions to sea level rise: “Protect Open”, “Protect Closed”, “Seaward” and “Move along”. It is stated that the current ‘Protect Open’ strategy – in which levees are raised to absorb the effects of sea level rise of more than +2m and high water flow in rivers is no longer tenable if sea ​​level continues to rise.

New locks and barriers must be built to ‘Protect Closed’, and if the sea level rises further, so much sand may need to be replenished that this strategy is also not tenable everywhere. To allow the continuation of the raising of the dykes and the construction of new locks and barriers in the long term, we must now reserve space.

A possible solution is “Seawards”, but in the long run this could be so expensive that it is not affordable for the Netherlands.

An example of the ‘Seawards’ solution direction is, for example, the construction of a new dike a maximum of 25 kilometers off the coast, the Haakse Zeedijk. This dike can be extended to France and Denmark. To make this possible, a lot of technical innovations are still needed and, above all, a lot of money. Such a solution works well in the Netherlands. The Haakse Zeedijk would not seem out of place in the list of dykes, reclamations, Zuiderzee works and Delta works.

In the event of a strong rise in sea level, we cannot at least partly avoid “moving” with the high waters. Why are new plans still being drawn up for the construction of houses in low areas? In current thinking about the planning of the Netherlands, should we no longer take into account the Meebewegen strategy, in which it is asked whether and how a new expansion area can be protected against a further rise in the level of the sea ? It may also offer solutions for other aspects of climate change: saline infiltration and absorption of extreme rainfall.

The choice could be to build more new houses on dry ground.

For centuries, buildings in our delta have been built on dry ground. On the crests of large rivers by the Romans, from the Middle Ages on mounds and wierden raised by the inhabitants themselves and of course on sandy uplands. It moved with the water.

But now, moving with the water goes against our national character. After all, the Netherlands defends itself against water. Specifying the country is not appropriate. This was clearly noticeable in the Hedwigepolder, which was returned to the Scheldt estuary as a natural compensation for the deepening of the Western Scheldt to maintain the accessibility of the port of Antwerp.

There is still a lot of uncertainty about what measures are needed to protect the Netherlands against further sea level rise. In any case, we must not make solutions impossible by now building houses in places whose we may need it when the time comes for the different strategies. We burden future generations with this.

Such an assessment cannot be made by local authorities. This is only possible if the national government takes control of the use of the water and soil system.

Central government proposals will also need to be considered as a whole. NOVI aims to address the problem in an integrated way, but it lacks clear objectives and therefore frameworks within which to work in the areas. Currently, central considerations for cross-cutting topics are missing.

In the letter from the Ministry of Infrastructure and Water Management dated 25 November 2010, Minister Habers explains how the Netherlands should manage water and land use in view of climate change . In addition to laudable starting points for the future use of the water and soil system, the approach to the solution is Rutte’s: many responsibilities are transferred to lower levels of government, with governments being jointly responsible for the result, where a central consideration for cross-cutting issues is needed. Due to a lack of direction from the central government, more “liquid” decisions will be made, as we see now with regard to housing in the Zuidplaspolder and many other polders.