Buzz
Missouri Army National Guardsmen are stationed along the top of a levee, overseeing the flooding Mississippi River. Joe Raedle/Getty Images.In the poem 'The Dry Salvages,' T.S. Eliot characterizes the river as 'a strong brown god,' a mighty and unpredictable force that can be both nurturing and ruthless. Over the ages, great cities have flourished on the banks of rivers and coasts, but this proximity means living alongside a powerful and untamable entity. Rivers have been known to wash away entire communities or alter their course, leaving once-prosperous civilizations to fade into history. Even today, ocean storms still pose a serious threat to centuries of human progress.
For thousands of years, humans have sought ways to manage fluctuating water levels. One of the earliest solutions has been the levee, also called a dike. A levee is a man-made structure designed to prevent a river from overflowing or to stop ocean waves from flooding unwanted areas.
In New Orleans, the levees serve two purposes: On one side, they shield the city from flooding by the Mississippi River, while on the other, they help keep Lake Pontchartrain's waters in check.
In certain regions of the Netherlands, dikes prevent the ocean from reclaiming vast areas of land, much of which is situated at or even below sea level. Holland's iconic windmills pump water out from behind these dikes and back into the sea, ensuring the land stays dry. In some areas of the country, known as polders, the Dutch have even managed to create new dry land by constructing dikes and draining the water.
A levee typically consists of a mound of soil that is less permeable, like clay, with a wider base and a narrower top. These mounds stretch out in long strips, sometimes extending for miles, alongside a river, lake, or the ocean. Along the Mississippi River, levees can stand between 10 and 20 feet (3 to 7 meters) tall, while in Holland, they can reach heights of up to 30 feet (10 meters). However, there is no standard height for levees; their size varies based on the severity of storms in the area, even those that occur once every century or millennium.
Living near water offers numerous benefits to humans, such as fertile farmland, convenient transportation, trade routes, and access to hydroelectric power. Levees make it possible for humans to take advantage of these resources without the constant threat of flooding. However, people often forget just how formidable the 'strong brown god' truly is.
When the Levee Breaks
A helicopter drops sandbags to seal a levee breach in New Orleans after Hurricane Katrina struck in 2005. Jerry Grayson/Getty Images News/Getty ImagesWhen walking along the beach or having a picnic by a river, it's easy to forget how immense Earth's waterways are—until floods and storms remind us of their power. In 1927, the Mississippi River surged under relentless rain, breaking through levees and flooding an area as large as Ireland. Similarly, in 1953, the North Sea overwhelmed the Netherlands' long-established system of dikes, claiming thousands of lives.
In 2005, the world turned its attention to New Orleans when Hurricane Katrina breached its levees. Situated 10 feet (3 meters) below sea level, much of the city has been developed on land reclaimed by draining its low-lying, swampy areas. However, as the land dried, it sank. Today, New Orleans relies on its levees and massive pumping systems to keep the waters at bay.
Hurricane Katrina devastated 80 percent of New Orleans, causing around 1,600 fatalities and displacing about 200,000 residents [source: Dolfman et al., Gonzales]. How did this happen? A study by the National Science Foundation uncovered five major contributing factors:
- Inadequate planning: The levee designs in New Orleans were based on a 1965 study, which was outdated. Engineers had aimed to create a levee system that could withstand the worst storm in 200 years. However, the study vastly underestimated the potential strength of future storms.
- Faulty design: Unlike neighboring regions, whose levees were designed for safety, New Orleans' levees were constructed to support the city's growth. This led to weaker and shorter levees.
- Bureaucratic inefficiencies: The maintenance of the levees was spread across various private firms and government agencies, with no central body in charge. This lack of coordination caused problems and delayed critical upgrades.
- Lack of maintenance: Levees require constant upkeep. As the land in New Orleans sank, the levees did as well. Investigators suspect that large nearby trees may have compromised the stability of the levees.
- Insufficient funding: The U.S. Army Corps of Engineers, responsible for designing and building levees, had been affected by budget cuts. These cuts left the agency with fewer experienced engineers.
As New Orleans works to rebuild after the disaster, many of these issues are finally being addressed. The Netherlands encountered a similar challenge following the 1953 flood. How do their successful measures compare with the failures in New Orleans?
Dikes of the Netherlands
The windmills of the Netherlands play a crucial role in pumping water away from behind the dikes and back into the sea, keeping the land dry.
© iStockphoto.com/pidjoeFollowing the devastating flood of 1953, Dutch engineers set out to design a new type of barrier to protect the land from the sea. Over time, they replaced the medieval-era dike system with 350 miles (563 km) of levees, which are now regarded by many as the safest in the world.
The Dutch revolutionized levee construction by reassessing their entire system in several significant ways:
- Thinking long term: Unlike the 1965 team of engineers in New Orleans, who built levees to withstand a storm that could occur once every 200 years, Dutch engineers designed a system capable of withstanding a catastrophic storm that might only occur once in 10,000 years.
- Reducing reliance on solid barriers: Instead of constructing ever larger barriers like levees and floodwalls, Dutch engineers focused on better ways to absorb floodwaters, using marsh plains and specially designed rivers. In some instances, they even moved the dikes further from the water.
- Innovative materials: The Dutch developed durable synthetic textiles to reinforce earthen levees. These materials help prevent soil movement and water penetration. Following Hurricane Katrina, New Orleans began using this technology for its levee system.
- Enhanced monitoring systems: In addition to maintaining stricter control and centralized upkeep of their dikes, the Dutch have implemented automated surveillance systems to monitor their levees' condition. Fiber-optic cables and electronic sensors embedded in the dikes relay data back to a central monitoring station, while additional systems track water pressure and levels.
The Dutch levee system is built on the understanding that effective levees require ongoing maintenance, continuous monitoring, and a long-term perspective on how rivers, oceans, and storms interact. When these principles are followed, communities can flourish in harmony with the natural beauty and benefits of coastal and riverside areas. It is only when we neglect these factors that rivers and oceans turn into destructive forces.
Explore the links below to discover more about storms, the ocean, and the remarkable achievements in both human and natural engineering.
