It’s all about understanding risk. This means understanding exactly how breaches in dikes and seawalls could lead to flooding in farms and cities–how deep the waters could get and how fast they might rise. It means understanding how those risks will change under various conditions, such as higher sea levels and different weather patterns. It means calculating how many people and how much property lie in the path of such floods, and how future changes in land use could worsen or mitigate any damage. Once they understand all that, the Dutch can plan, build, and fortify in ways that meet specific local needs. This could mean designating certain areas as no-build zones, developing new building techniques, adding floatable roadways as escape routes, or replacing farms with floating greenhouses. All this represents a major shift in focus, from preventing floods to minimizing damage when they occur. “You are looking at a different type of planning,” says Pieter Bloemen, a program manager with the Netherlands’ National Spatial Planning Agency.
Historically, the Netherlands–like most other countries– has thought about disaster protection in simple but reassuring terms. The Netherlands’ North Sea flank is sheltered by great seawalls and tidal-surge barriers erected after a 1953 flood that killed nearly 2,000 people. The strongest of these were engineered to withstand all but the rarest disasters: floods that have only a 1-in-4,000 chance–even a 1-in-10,000 chance–of happening in a given year. But these probabilities were calculated around 1960 and are understood to be obsolete. What’s more, the Dutch population surged from 11.5 million in 1960 to 16.6 million this year, greatly raising the stakes. “Most people in the Netherlands have the idea they are safe from flooding, because of all the investment,” says Hans Balfoort, a senior policy advisor in the Netherlands’ Ministry of Transport, Public Works, and Water Management in The Hague. “It gives people a false idea of absolute protection.”
The Dutch program for intensive risk analysis and planning is gaining attention in geographically similar parts of the world, including the Mississippi River Delta in Louisiana and the Sacramento River Delta in California. “There is a lot of pressure that places like New Orleans should adopt this kind of approach for planning and protection,” says Rafael Bras, a hydroclimatologist at MIT. He notes that in the U.S., as in the Netherlands, planners and engineers have historically focused on the strength of seawalls and levees, not the extent of the destruction that could occur if they failed. “In the past, our approach has been, ‘We will protect to a certain-level hurricane,’ without trying to translate that into, ‘What does that mean in terms of risk to the population?’”
Dams of Rotterdam
The risk analysis the Dutch are performing requires basic information about the country’s network of seawalls and dikes, but collecting it is no easy task. Much of the nation was reclaimed from the sea piecemeal over the past 800 years: farmers drained land, dug canals, and built dikes, giving rise to the saying “God made the world, but the Dutch made the Netherlands.” Local democratic bodies called water boards–hundreds of them–emerged to manage and maintain flood barriers and pumping stations. But the accretion of locally built fortifications did not leave a legacy of centralized, accurate records. “We are not Swiss,” laments Jaap Kwadijk, a geologist with the engineering firm Delft Hydraulics.
To understand how un-Swiss the Dutch are, consider the political history of the southwest polder, the area near Gouda where the 4,000 houses may rise. Historically, a chunk of the polder was managed by a water board called the Schieland, organized in 1273. An adjacent water board, the Krimpenerwaard, was founded in the 1430s, cobbled together from smaller boards. Dramatic change came in 2005. After 535 years of peaceful coexistence, the Krimpenerwaard joined with the Schieland. The merger is marked by a prominent sign inside the region’s biggest pump house, designating the board the “Hoogheemraadschap van Schieland en de Krimpenerwaard.” Pump-house engineer Harry Berkouwer, whose family has lived for more than 600 years in the hamlet of Berkenwoude (its name means “birch forest”; his means “birch cutter”), beams when he speaks of the event.