Learning to Battle Rising Seas from the Dutch

In 1609, the English maritime explorer Henry Hudson arrived in New York Harbor on an expedition for the Dutch.

Four hundred years later, as New York City faces the ramifications of climate change, it is learning from the Dutch how to manage rising sea levels, which could rise as much as 55 inches by 2100.

On September 9th and 10th, a conference in New York City will examine the challenges coastal cities face in the 21st century. Held by the Henry Hudson 400 Foundation, the H209 Forum will bring together leaders from both the U.S. and the Netherlands, a country that has long battled flooding, with more than a quarter of its lands lying below sea level.

“It’s a good chance to look into the Dutch water case – how do they do it? Obviously, the Netherlands has had a long history of struggling and living with the water,” says Gert Tetteroo, the executive director of the Henry Hudson 400.

Although New York City sits above sea level, it has important infrastructure, including its subway system and traffic tunnels, below sea level. Also, parts of downtown are only 1.5 meters, or 59 inches above sea level. As sea levels rise, the city will become more susceptible to dangerous storm surges and the flooding they would bring.

The New York City Panel on Climate Change says sea levels could rise 12 to 23 inches by 2100, according to current general circulation models (GCM), the software programs used to project future climate. They show that warmer water will expand, causing the seas to rise two to five inches by the 2020s, and 7 to 12 inches by the 2050s.

However, most GCMs do not account for recent developments such as accelerated ice melt in Greenland and Antarctica. So, PlaNYC 2030, the city's sustainability plan which contains strategies to adapt to and mitigate climate change, also makes projections that take these phenomena into account. Then, it’s possible that sea level rise could accelerate and reach as high as 41 to 55 inches by the 2080s, and coastal floods that are currently expected to happen once every 10 years, could happen every one to three years.

Some other American cities dealing with the likelihood of increased flooding include the San Francisco Bay Area, the Sacramento-San Joaquin Delta, Miami, and most prominently, New Orleans.

Piet Dircke, a director for water management for the Dutch company Arcadis, says experts in the Netherlands have found three types of tools can protect against rising seas:

• infrastructure,
• natural systems that combine civil engineering and water management techniques,
• and smart technologies.

“Storm surge barriers like we have in the Netherlands are good solutions,” he says, “but they are the last option you should consider, because they are very expensive and very complicated technically, and they need a very high level of operational maintenance.”

Using natural systems to prevent flooding, called ecomorphology, involves improving sediment flow by placing sediment at scientifically determined sites along the coast. The Dutch have also begun a program called Room for the Rivers, which gives more room to the land around rivers to flood where the water will cause the least damage. For instance, dikes can be moved further away from rivers, allowing more space for flooding, or side channels can be created next to rivers to create more areas for water to pool. The banks between the river and the dike can also be lowered, forming more space for floodwaters.