Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Lorn Bogelbaum here in his poem The Dry Salvages, T. S. Eliot described the river as a strong, brown god, a powerful force that, while often patient and nurturing, proves itself untamable and merciless. The greatest cities in human history have risen up on the banks of rivers and by the seaside, but in doing so, their builders chose to live in
close confines with an unruly force. Rivers have surged, washing away whole communities or changed course, abandoning prosperous kingdoms to the dust. Even today, ocean storms threatened to decimate centuries worth of human endeavor. Humans have attempted to conquer the problems of changing water levels for thousands of years. One of the oldest weapons we've wielded against the rivers and
oceans is the levee, also known as a dike. A levee is simply a man made embankment built to physically block a river from overflowing its banks, or to prevent ocean waves from washing into undesired areas. In New Orleans, for example, the levees attempt to perform dual duties. On one side of the city, levees protect against floods from the Mississippi River, and on the other side they help
to keep lake punch train in place. In parts of the Netherlands, dikes stop ocean waters from reclaiming thousands of miles of land, much of which is either at or below sea level. The famous windmills of Holland pump water from behind the dikes and back out to sea to keep the land dry. As in Louisiana and for another example, the Florida Everglades region, there are parts of the Netherlands where engineers have created new dry land with complex water
management systems. A levee is typically little more than a mound of not very permeable soil like clay, wider at the base and narrower at the top, but they can be a little or a lot more complex, comprised of different layers of soils, especially designed fabrics to reinforce the soil, concrete floodwalls, pump stations to control water levels, and all
kinds of sensors to help watch four potential problems. They can feature paved paths and gates for pedestrian and vehicle traffic bridges, and even parks with landscaping and esthetic architectural features, you might not even realize that what you're standing on is part of a levee system. Levees often run in a long strip, sometimes for many miles, along a river, lake, or ocean. Just for example, levees along the Mississippi River may range from ten to twenty feet tall that's about
three to seven meters. In Holland, they can top thirty feet that's ten meters, but there's no set height for levees. Their measurements vary according to storms that the area receives, even if those storms occur only once every hundred or one thousand years. Every levee system is different based on the particular conditions and risks in an area. They can incorporate salt water or freshwater marshes to help absorb flooding.
Coastal systems especially may be helped by periodic beach renourishment to replace sand, soil, and rocks that are eroded during storms, and levee systems can be built in conjunction with dams to better manage a whole area's watershed. A living by the water provides humans with a number of advantages a fertile farmland, transportation, trade, and hydroelectric power. Levees allow humans
to enjoy these assets with less fear of flooding. While strolling along the beach or enjoying a picnic by a riverbank. It's easy to forget the strength of water until floods and storms jar us to remember. In nineteen thirteen, the Ohio River and its tributaries flooded, submerging several cities and killing one thousand. In nineteen twenty seven, the Mississippi River swelled during several months of heavy rain, charging through a line of levees and flooding an area the size of Ireland,
displacing hundreds of thousands of Southerners. In nineteen fifty three, the North Sea broke through netherlands ancient system of dikes and killed thousands. Through these and other disasters, our scientific understanding of waterways evolved. Engineers now operate with the base concept that water cannot be fully controlled, but can be mitigated through broad and interconnected flood risk management systems. But even with this understanding, disasters still happen. Back in two
thousand and five, Hurricane Katrina breached New Orleans levees. Much of the city lies below sea level. Throughout history, low lying boggy areas have been pumped dry to create new land. Much of this reclaimed land has sunk as it dried out. The entire city now depends on the levees, along with massive pumping stations to keep the water out. Katrina flooded eighty percent of the city, killing some one thousand, six hundred people and displacing about two hundred thousand others. But
how could this happen in a modern city. Investigations over the following decade pointed to a few major reasons. First, there was insufficient planning. New Orleans levee designs were based on an outdated study from nineteen sixty five. Engineers built the system with the goal of standing up to the worst storm possible in two hundred years. Unfortunately, the study greatly miscalculated how powerful potential storms could be. Second, the
design was risky. New Orleans levees were built to sustain the city's growth, unlike the levees and neighboring areas, which were built to provide safety. As result, New Orleans levees were shorter and weaker. Third, the safety of the system was compromised by bureaucracy. No central agency was in charge of maintaining the levees. This task instead fell to several different private firms and government agencies, leading to communication problems
and the breakdown of various upgrade projects. Fourth, there was poor maintenance. Levees require constant upkeep. As the land in New Orleans sinks, so do the levees. And Fifth, there were insufficient funds. The US Army Corps Engineers, which oversees the design and construction of levees, had been hit by budget cuts. This left the agency with fewer experienced engineers. As New Orleans rebuilt from the disaster, some of these
concerns were addressed. The Army Corps Engineers designed a system of floodwalls and levees snaking three hundred and fifty miles that's five hundred and fifty kilometers through five parishes, at a cost of over fourteen billion dollars. However, that was now twenty years ago and maintenance is an ongoing issue. They estimate that it'll cost another billion dollars in upkeep over the next fifty years, and that kind of funding is frustratingly hard to come by. The Netherlands faced a
similar situation following the flood in nineteen fifty three. In the decades that followed, engineers set out to build a new kind of barrier against the sea. They steadily replaced the old dike system which had been in place since the medieval ages, and created, weirdly enough, right around three hundred and fifty miles of what many consider the safest levee system in the world. They started by reevaluating their entire system in several key ways. They set out thinking
long term, like really long term, new orleands. Old levees were built to with stand the strongest possible storm in two hundred years. Netherlands engineers designed a system strong enough to match the kind of catastrophic storm that only occurs once in ten thousand years. Also, instead of constructing increasingly bigger solid barriers like levees and flood walls, they sought to create better ways of absorbing floodwaters in marsh plains
and specially constructed rivers. In some cases, this involved setting dikes farther back from the water. The engineers also developed tough synthetic textiles to better anchor earth than levees These prevent soil movement and water penetration. The New Lands Levee system began using this technology following Hurricane Katrina. The Netherlands also implemented more stringent and centralized control and maintenance of their dikes and now use automated surveillance systems to keep
an eye on how their levees are holding up. They installed fiber, optic and electronic sensors in dike structures to report changes back to a central monitoring system. The several other systems monitor water pressure and water level. A major challenge in maintaining levee systems in urban areas is urban sprawl, which can place increased pressure on existing levee structures. Levees require regular maintenance, constant monitoring, and a long term appreciation
for how rivers, oceans, and storms behave. When these are in place, communities can thrive safely along the beauty and convenience of coastal and riverside areas. It's when we fail to remember this that rivers and oceans become destroyers. Today's episode is based on the article what is a levee? On HowStuffWorks dot com, written by Marshall Brain and Robert Lamb brain Stuff is production of iHeartRadio in partnership with how stuffworks dot Com and is produced by Tyler Klang.
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