Possible measures for sea level rise in the future
We have been witnessing the effects of climate change more and more often, and ever more clearly, in recent years. The Netherlands is no exception: extreme rainfall, heat waves, drought, flooding and sea level rise. It is still uncertain how high and how fast sea levels will rise in the future and the answers depend largely on global warming and the stability of the ice sheets. Deltares was commissioned by the Delta Commissioner and the Minister of Infrastructure and Water Management to look at the measures the Netherlands can take now to cope with sea level rise in the future.
Why take steps now in anticipation of uncertain sea level rise in the future?
Accelerated sea level rise will probably begin to require drastic measures only in the latter half of this century. Nevertheless, it is important to take this into account in the next decade in the major investment agendas that are being planned for areas including housing, agriculture and the energy transition. By preserving or creating enough room to manoeuvre in these agendas for future sea level rise, we can prevent or reduce future damage, casualties and costly adaptation measures for future generations.
Building blocks for improving flood risk management
The new study is a follow-up to previous analyses by Deltares of the possible consequences of accelerated sea level rise (2018) and the potential solutions (2019). It shows that anticipating sea level rise implies making important decisions about coastal management, exploiting the natural sedimentation of sand and silt, and discharging river water. This follow-up study describes 22 possible measures that can be thought of as building blocks for future solutions and adaptation pathways. These include hard and soft flood defences, river measures, changes to land use and “avoidance and relocation”. The building blocks focus primarily on flood protection and they will be extended at a later stage to include building blocks for freshwater supplies.
Deltares has explored where these building blocks can be applied, in which combinations, and whether it is wise to start doing so now (in a low-regret approach). For example, creating space for water storage and the discharge capacity of rivers, raising water levels in peatland areas to prevent land subsidence, and earmarking space for dike upgrades.
Central role for river area
Higher sea levels will also lead to rising water levels in the Rhine-Meuse estuary area. Dikes will have to be raised in an area where space is at a premium. A possible alternative is to close the New Waterway in the future with a dam that will include a lock complex and pumping system. Should this happen, the Rhine and Meuse will no longer drain freely to the sea. As in the case of the IJsselmeer lake, an inland lake will form behind the barrier. As sea levels continue to rise, more and more pumping capacity will be required to maintain flood protection. The capacity required will be many tens of times larger than the capacity of the recently completed pumping system in the IJmuiden locks. That requires a lot of space.
Sea Level Rise Knowledge Programme
This study is being conducted as part of the Sea Level Rise Knowledge Programme. The Sea Level Rise Knowledge Programme brings together government authorities, knowledge institutes, business, stakeholder organisations and committed citizens to work together on strategies in order to be prepared for a accelerated sea level rise in the future. The programme was commissioned by the Delta Commissioner and the Minister of Infrastructure and Water Management.
This report is part of track IV, which focuses on the action perspective for a distant future.