Climate change adaptation: What we can learn from the Dutch masters
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No country in the world is more aware of the dangers of rising sea levels and overflowing rivers than the Netherlands, also a giant delta. Over the course of history, it has learnt to successfully mitigate the hazard of both coastal flooding from storm surge and river water discharge. With its expertise in building dykes, dunes, dams and barriers, the Netherlands has been able to increase agricultural land and become the second-largest agricultural exporter by dollar value in the world.
Today, the country faces combined threats of climate change and ever-increasing subsidence. Sea levels are rising; extreme rainfall events today occur twice as often as 50 years ago; and a third of the Netherlands lies below sea level and vast swathes are gradually sinking (subsiding) under the weight of the centuries-old practice of saltwater drainage and land reclamation to make the lowlands suitable for agriculture and other land use.
Faced with the prospect of rising sea and precipitation levels, the Dutch government has reformulated its policies on flood protection and water management, from one focused only on reducing the hazard to a more comprehensive risk-based and adaptive approach. A wide range of adaptation measures based on both water management and sustainable spatial planning have been devised. In addition, climate risk is continuously assessed, and the policy is redefined as new scientific information about an evolving physical risk landscape and the impact on flood risk is made available by the scientific community.
Already in 2007, in a reversal of the centuries-old practice of land reclamation, the government launched the "Room for the River" programme to reduce water levels during times of high river discharges, by creating extra storage facilities (lakes, parks and even parking garages) along the rivers and increasing the retention capacity of urban areas. Instead of keeping the water between ever-higher dykes and discharging it into the sea as fast as possible, the idea is to "accommodate the river water."
During intense rainfall these extra storage spaces will retain water, and at other times serve as playing fields and communal areas. Among the most recent measures are the creation of additional flood channels (bypasses or "green rivers"), increasing the depth of flood channels and removing obstacles from the floodplain, but also floating roads, buildings and structures that adapt to changing water levels. The challenge is balancing between water levels that allow optimum land use while minimizing subsidence. In 2010, the government further strengthened its action on the water domain within the national framework of the Delta Programme. The aim is to make flood risk management, freshwater supply and spatial planning climate-proof and water-resilient by 2050, ready to deal with both extreme flooding and drought.
Pan-European rainfall deficits in the summer of 2018 caused a national water shortage with severe consequence for agriculture (economic losses of EUR 1.4 billion). Due to the role that Rotterdam plays in the shipping sector, the low level of the rivers Waal, Ijssel and Lower Rhine triggered transportation disruption and further losses of EUR 354 million.
The drought came as a shock in the land of aquatic plenty and reinforced the urgency to press ahead with the freshwater supply measures within the Delta Programme. The experience also reinforced that fighting climate change requires a fully integrated holistic approach, where response is adaptive to new developments (from multiple hazards and the risk side). Or else, when building any mitigation measures with a non-adaptive static view, they run the risk of being outdated by the time they are completed.
Windstorms are another peak weather-related natural catastrophe risk in Europe. There has been a lull in large-scale storm disasters in recent years, but the 1999 storm series of Lothar and Martin, and the North Sea storm surge in 1953, remain significant tail risk events. The risk is dominated by strong natural variability: the history of European windstorms shows a strong multi-decadal pattern.