Central Holland is located between the IJsselmeer area, the coast and the river area. It includes the metropolitan regions of Utrecht and Amsterdam and the Green Heart. From the river area, the Amsterdam-Rhine Canal runs through Central Holland into the North Sea Canal. The locks, and the pumping and discharge complex, in IJmuiden connect the canal to the North Sea. Central Holland, with about 4 million inhabitants, is home to nearly a quarter of the Dutch population.
The area makes a crucial contribution to the economy day and night, and it is undergoing a makeover for a large number of national and regional building and development agendas. At the same time, it is very vulnerable: the sea level is rising and the land is subsiding. The area is very vulnerable to problems with excess water and water shortages. The size, complexity and orchestration of the agendas in the area require a broad-based societal assessment. The Central Holland Delta Programme brings together the agendas for flood risk management, excess water, fresh water and spatial adaptation, and relates them to the transregional water system and spatial agendas.
In the short term, large-scale spatial developments are planned for Central Holland in response to urban development, the agricultural transition, nature development, sustainable energy supplies and the increase in economic activity and mobility, and the reorientation of the port of Rotterdam. The developments are putting pressure on space in the area, much of which is below sea level. At the same time, all these developments are also having a major impact on the water system, which has already reached its limits.
Central Holland’s current water system and spatial planning are not robust enough to absorb the effects of climate change in combination with the major societal challenges. In the current situation, this means there is already a significant risk of damage as a result of excess water and water shortages. To keep its feet dry, the area depends almost entirely on one drainage point: the IJmuiden pumping and discharge complex on the North Sea coast. In normal circumstances, maintaining water levels within the margins depends very much on the possibility of discharging water to the North Sea. Even a slight rise in the water level can lead to problems. This effect will be exacerbated in the years ahead because of rising sea levels. Extreme precipitation will increase but the area cannot handle large amounts of rainfall of the magnitude seen in Limburg in the summer of 2021.
Shortages of fresh water will also soon lead to problems in Central Holland. That will lead to damage – aridification, salinisation and land subsidence – and adverse effects on agriculture, drinking water supplies, nature, shipping, buildings and infrastructure. In times of drought, there is not enough water for all user functions. A freshwater shortage in 2022, for example, caused ecological damage, as well as severe restrictions on, and economic damage for, commercial and recreational shipping. Situations in which salt concentrations are high will, in all probability, become more frequent. In addition, a further increase in freshwater demand would also seem to be on the cards.
The area is therefore on the eve of major spatial developments in response to the housing agenda, the energy transition, economic development in the Rotterdam port area and the mitigation of land subsidence in the peatland area. These developments must be tailored to the water and soil systems for the purposes of site selection and be sufficiently adaptive.
Coordination with other studies and processes
The regional programme Future-Resilient Water System in the Amsterdam-Rhine Canal/North Sea Canal Area (TB ARK/NZK Area) is investigating bottlenecks and possible solutions for problems with excess water and water shortages, salinisation and spatial impact in Central Holland between now and 2100. This involves coordination with other programmes, such as the Sea Level Rise Knowledge Programme. In track IV of the knowledge programme, the implications of sea level rise in the long term for the spatial functions in the area, and how this will affect the choices and agendas in the current area processes, are being investigated in collaboration with local partners. In order to allow water to serve as a leading factor for spatial planning, the water partners are working on clear boundary conditions that spatial developments must meet, for example as part of the NOVEX processes. In addition to the retention and/or storage of water, all spatial developments must capture water discharge and increases in precipitation in their ‘own area’. In addition, the TB programme is looking at the utility, necessity, technical feasibility and costs of the construction of new pumping stations to discharge excess water to the Markermeer lake or Lek/Waal rivers to compensate for the decline in discharge potential at IJmuiden. The Climate-Resilient Freshwater Supplies in the Main Water System (KZH) programme is investigating, on the basis of the Freshwater Delta Programme, whether a new pumping station could also bring water from the Amsterdam-Rhine Canal to the IJsselmeer area in order to be prepared for impending water shortages. Finally, stress tests have been conducted in a range of working regions and they are being formulated as adaptation strategies.
Supra-regional coordination and orchestration
Solutions for a future-resilient – robust, adaptive and transformative – Central Holland transcend the water system. The agenda is too large and water awareness is too low. People need to realise more that not everything can be done everywhere. On the basis of the principles of ‘Water and Soil as Leading Factors’ and a long-term perspective based on the challenges associated with sea level rise, decisions are needed about which user functions fit in with the long-term capacity of the water and soil system. Where can housing be built? How can construction be made climate-resilient? Which water storage arrangements, drainage capacity and safety standards are needed to protect the area?
Action must also be orchestrated beyond the borders of Central Holland, in conjunction with other areas and processes of the Delta Programme such as the Sea Level Rise Knowledge Programme and the Freshwater Delta Programme, and with the neighbouring IJsselmeer and River areas. That is because many functions in the area depend on the availability of adequate supplies of good fresh water and the possibility of drainage. Sea level rise also results in spatial challenges and choices that will continue to have an effect in the distant future.
The Central Holland area is bringing together the building blocks from all processes and sub-programmes in order to prepare for joint decisions and make capital-intensive interventions from the perspective of water and space that do justice to the area’s current value and future development.