Holding Back the Floods

Perhaps no country on Earth has as much experience protecting against floods as the Netherlands. About a third of the small European nation’s land is below sea level—and much of that area would be underwater if not for centuries of expert engineering. “Flood protection is a huge part of our history and culture,” says Harold van Waveren, a senior adviser for the Dutch government’s flood-prevention agency. “Without it, our country wouldn’t exist.”

Van Waveren lives near Amsterdam at a depth of 5 m (16 ft) below sea level in a polder—an area surrounded by walls, called dikes, that keep water out. The country has nearly 3,500 polders, protected by 40,000 kilometers (25,000 miles) of dikes and dams.

The Netherlands is a small nation in Europe. It may have more experience with flood protection than any other country. About a third of its land is below sea level. Much of that area would be underwater, but expert engineering keeps it dry. “Flood protection is a huge part of our history and culture,” says Harold van Waveren. He’s a senior adviser for the Dutch government’s flood-prevention agency. “Without it, our country wouldn’t exist.”

Van Waveren lives near Amsterdam. His home is 5 m (16 ft) below sea level in a polder. That’s an area surrounded by dikes. These walls keep water out. The country has nearly 3,500 polders, and 40,000 kilometers (25,000 miles) of dikes and dams protect them.

Flood protections have continued to evolve since Dutch farmers built the first dikes a thousand years ago. A major storm in 1953 that flooded the southwest Netherlands and killed 1,800 people motivated the country to build the massive Delta Works. This project constructed new barriers and dams to protect against storm surges—increases in sea level due to wind and air pressure changes during storms. The project also included channels called sluices, which drain excess water during floods.

The crown jewel of the Delta Works is the Maeslantkering (MAHS-lawnt-keh-ring), a giant barrier completed in 1997 that protects Rotterdam, one of the world’s busiest ports, from the sea. Ships must enter and exit the port, so building a permanent barrier that blocked the sea wouldn’t work. Instead, the government decided on a huge gate that remains open most of the time and swings shut during storms (see The Netherlands’ Giant Sea Gates).

Dutch farmers built the first dikes a thousand years ago. Flood protections have evolved since then. In 1953, a major storm flooded the southwest Netherlands and killed 1,800 people. This prompted the country to build the huge Delta Works. The project included new barriers and dams to protect against storm surges. These rises in sea level come from wind and air pressure changes during storms. The project also included channels called sluices. They drain excess water during floods.

The crown jewel of the Delta Works is the Maeslantkering (MAHS-lawnt-keh-ring). This giant barrier was finished in 1997. It protects Rotterdam, one of the world’s busiest ports, from the sea. Ships must enter and exit the port. So a fixed barrier that blocked the sea wouldn’t work. Instead, the government chose a huge gate that usually stays open. It swings shut during storms (see The Netherlands’ Giant Sea Gates).

The Maeslantkering successfully held back the sea during a 2007 storm. But storm surges aren’t the Netherlands’ only flood threats: In 1995, dikes surrounding the narrow Waal River nearly failed during heavy rains, threatening the city of Nijmegen (NYE-may-ken). Some 200,000 people evacuated. “That led to a big change in our strategy,” says van Waveren. “Until then, we thought we could manage nature and have it do as we wanted. But we realized nature is sometimes stronger than we are. We had to stop fighting it and find ways to work with it.”

Current flood protection strategies in the Netherlands focus on allowing nature to safely take its course during floods. Workers are restoring and protecting coastal lands like beaches, marshes, and dunes, which provide natural buffers against storms.

A storm struck in 2007, and the Maeslantkering held back the sea. But storm surges aren’t the Netherlands’ only flood threats. In 1995, heavy rains fell. Dikes around the narrow Waal River almost failed. The city of Nijmegen (NYE-may-ken) was in danger, and some 200,000 people evacuated. “That led to a big change in our strategy,” says van Waveren. “Until then, we thought we could manage nature and have it do as we wanted. But we realized nature is sometimes stronger than we are. We had to stop fighting it and find ways to work with it.”

Now flood protection methods in the Netherlands have a new focus. They allow nature to safely take its course during floods. Workers are fixing and protecting coastal lands like beaches, marshes, and dunes. These areas are natural barriers against storms.

At more than 30 sites around the country, engineers are also creating additional places where water can go. The city of Nijmegen is part of this program, which is called Room for the River. There, workers recently built an extra channel so river water can flow around the city when the level rises. Low-lying areas are being turned into parks, gardens, sports fields, and other amenities that can act as reservoirs for floodwaters in emergencies without harming people or infrastructure. Builders are also moving dikes farther from the river to create additional space for floodwaters.

Engineers are also working at more than 30 sites around the country. They’re creating extra places for water to go. The city of Nijmegen is part of this program, which is called Room for the River. Recently, workers built an extra channel there. It lets river water flow around the city. Low-lying areas are being turned into parks, gardens, sports fields, and other features. They can hold floodwaters in emergencies. Builders are also moving dikes farther from the river. This makes more space for floodwaters.

On the coast of Texas, the U.S. Army Corps of Engineers (USACE) is investigating similar plans to combat storm surges. “The biggest element we’re considering is a large gate structure in the Houston-Galveston area that could be closed if a storm is coming,” says Sharon Tirpak, who is overseeing the study. One possible design resembles the Maeslantkering. “If it’s chosen, it would be one of the largest structures in the world,” she says.

The U.S. Army Corps of Engineers (USACE) is looking at similar plans. They need to protect against storm surges on the coast of Texas. Sharon Tirpak is running the study. “The biggest element we’re considering is a large gate structure in the Houston-Galveston area that could be closed if a storm is coming,” she says. One possible plan looks like the Maeslantkering. “If it’s chosen, it would be one of the largest structures in the world,” she says.

For storms like Harvey that dump massive amounts of rain, a sea gate would do little to stop flooding. So the Texas study is also evaluating how natural features like wetlands could help absorb heavy rains. The fact that so much of Houston is covered in concrete is one reason it flooded so badly, says Henk Ovink, the Dutch special envoy for water affairs. His job is to share Dutch expertise in flood management with countries around the world. Restoring native prairies and wetlands, which can soak up water, could help protect Texas and other areas against future floods.

A team from USACE recently visited the Netherlands to tour Dutch coastal defenses. And Dutch flood engineers came to the U.S. to compare methods for evaluating the stability of levees—our version of dikes.

Ovink says the challenges ahead represent an opportunity for coastal communities to come together to innovate. “In the form of rising seas and storms, water gives a tangible meaning to climate change that we have to prepare for,” he says. “But we can do this. It doesn’t have to be something we fear.”

Storms like Harvey dump huge amounts of rain. A sea gate wouldn’t stop that kind of flooding. So the Texas study is also looking at natural features like wetlands. It’s figuring out how these could help soak up heavy rains. Much of Houston is covered in concrete. That’s one reason it flooded so badly, says Henk Ovink. He’s the Dutch special envoy for water affairs. His job is to share Dutch knowledge and skill in flood management with countries around the world. Native prairies and wetlands can soak up water. Restoring them could help protect Texas and other areas against future floods.

Not long ago, a team from USACE visited the Netherlands to see Dutch coastal defenses. And Dutch flood engineers came to the U.S. to meet with engineers here. They compared ways of checking the strength of levees. Those are our versions of dikes.

Challenges lie ahead. But Ovink says they are an opportunity. Coastal communities can come together to find new ideas. “In the form of rising seas and storms, water gives a tangible meaning to climate change that we have to prepare for,” he says. “But we can do this. It doesn’t have to be something we fear.”