Recommendation from the Delta Commissioner: take the climate of the future into account in housing construction

When new locations are being selected for housing construction, hardly any thought is given to the soil and water system, or the consequences of climate change, particularly in the long term. An estimated 820,000 new homes are planned in flood-prone areas, areas with soft soil, or wetlands. These locations are susceptible to flooding, problems with excess water, land subsidence, drought and heat. This exposure will increase due to climate change and we will be faced increasingly with extreme weather, peaks in river discharge, and sea level rise.

This is the picture painted by Delta Commissioner Peter Glas in his second advisory letter on housing construction and climate adaptation that he submitted to the Ministries of the Interior, and Infrastructure and Water Management. He notes that targets for housing construction do not adequately take into account the long-term consequences of climate change and the requirements of water and soil. 

We need new housing quickly but it is important here for us to get it right the first time, to build in flexibility, and not to block the options of future generations by imposing problems and damage. The recent floods in Limburg demonstrated how vulnerable we are in the built environment. I am therefore calling for a closer look at where we plan to build and how we will build.

Sea level rise

The housing plans in place at the moment will result in a further concentration of housing in the low-lying Randstad area. In itself, this makes sense: this is where there is most demand for housing. But this is an area that will be increasingly exposed in the long term to the effects of sea level rise and land subsidence, and where the potential safety risks are highest. 

Taking long-term climate change into account is necessary because homes are generally built to last for 50 to 100 years, and the roads and public facilities for those homes often have an even longer lifespan. 

The Delta Commissioner says that, in addition, we should already be thinking about urbanisation in a more distant future. He advises the national government to look at how this urbanisation can, in time, be distributed differently over the Netherlands to include locations that are less vulnerable to climate change and sea level rise.

In the advisory letter, for which Sweco, Defacto, Deltares and Ecorys supplied data, the Delta Commissioner calls on national and regional government authorities to ringfence space for the measures that will be needed if sea level rise in the future reaches 2 metres in the North Sea. Space should also be earmarked in the unprotected areas outside the dikes alongside the major water bodies and rivers. That room is needed for future upgrades to the primary flood defences, for additional water storage and for the proper discharge of the water. 

The Sea Level Rise Knowledge Programme will publish the calculations next year for the additional space required alongside the primary flood defences. The report from Sweco, Defacto, Deltares and Ecorys shows that spatial planners and water managers must in any case keep in mind that an additional area of 20 to 50 metres will be earmarked for future dike upgrades. 

Housing outside the dikes

Outside the dikes along the rivers, it is important to avoid building housing that will restrict the flow of water and the room for water storage, now and in the future in particular. The Delta Commissioner advises the national government to consider tightening up the current regulations for building housing outside the dikes. He also advises the authorities to look at existing buildings outside the dikes as well. If those buildings impede discharge and water storage in the future, they should be adapted or possibly removed over time.

Buildings outside the dikes in the IJsselmeer area must not lead to restrictions on possible water level increases or the freshwater buffer. The Delta Commissioner also advises not building in locations where water accumulates during extreme precipitation or where it cannot be discharged temporarily, as in the brook valleys and lower-lying areas in polders. According to the Delta Commissioner, it is also necessary for building plans to take into account the capture of large amounts of rainwater during rainstorms by creating options in these plans for water storage and the infiltration of the water into the soil.

Furthermore, the Delta Commissioner calls attention to construction in areas with soft soils (where settlement is more likely). Additional measures are needed when preparing land for construction in these areas in order to prevent the subsidence of homes and roads. He also advises making groundwater-neutral housing construction mandatory to prevent the long-term effects of aridification, salinisation, and land subsidence.