WEBVTT - How Do Levees Protect Us? 0:00:01.840 --> 0:00:07.960 Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Lorn 0:00:08.000 --> 0:00:13.000 Bogelbaum here in his poem The Dry Salvages, T. S. 0:00:13.039 --> 0:00:17.000 Eliot described the river as a strong, brown god, a 0:00:17.239 --> 0:00:21.279 powerful force that, while often patient and nurturing, proves itself 0:00:21.400 --> 0:00:26.200 untamable and merciless. The greatest cities in human history have 0:00:26.320 --> 0:00:29.160 risen up on the banks of rivers and by the seaside, 0:00:29.320 --> 0:00:32.519 but in doing so, their builders chose to live in 0:00:32.600 --> 0:00:38.000 close confines with an unruly force. Rivers have surged, washing 0:00:38.080 --> 0:00:42.800 away whole communities or changed course, abandoning prosperous kingdoms to 0:00:42.800 --> 0:00:47.560 the dust. Even today, ocean storms threatened to decimate centuries 0:00:47.600 --> 0:00:51.519 worth of human endeavor. Humans have attempted to conquer the 0:00:51.560 --> 0:00:56.200 problems of changing water levels for thousands of years. One 0:00:56.240 --> 0:00:59.040 of the oldest weapons we've wielded against the rivers and 0:00:59.080 --> 0:01:02.640 oceans is the levee, also known as a dike. A 0:01:02.720 --> 0:01:06.240 levee is simply a man made embankment built to physically 0:01:06.280 --> 0:01:09.279 block a river from overflowing its banks, or to prevent 0:01:09.319 --> 0:01:14.520 ocean waves from washing into undesired areas. In New Orleans, 0:01:14.520 --> 0:01:18.400 for example, the levees attempt to perform dual duties. On 0:01:18.400 --> 0:01:20.920 one side of the city, levees protect against floods from 0:01:20.959 --> 0:01:23.920 the Mississippi River, and on the other side they help 0:01:23.959 --> 0:01:27.640 to keep lake punch train in place. In parts of 0:01:27.680 --> 0:01:31.319 the Netherlands, dikes stop ocean waters from reclaiming thousands of 0:01:31.319 --> 0:01:33.840 miles of land, much of which is either at or 0:01:33.920 --> 0:01:37.920 below sea level. The famous windmills of Holland pump water 0:01:38.040 --> 0:01:40.200 from behind the dikes and back out to sea to 0:01:40.360 --> 0:01:44.920 keep the land dry. As in Louisiana and for another example, 0:01:45.000 --> 0:01:48.160 the Florida Everglades region, there are parts of the Netherlands 0:01:48.200 --> 0:01:52.200 where engineers have created new dry land with complex water 0:01:52.280 --> 0:01:56.440 management systems. A levee is typically little more than a 0:01:56.480 --> 0:02:00.800 mound of not very permeable soil like clay, wider at 0:02:00.840 --> 0:02:04.000 the base and narrower at the top, but they can 0:02:04.080 --> 0:02:07.400 be a little or a lot more complex, comprised of 0:02:07.400 --> 0:02:11.480 different layers of soils, especially designed fabrics to reinforce the soil, 0:02:11.880 --> 0:02:15.760 concrete floodwalls, pump stations to control water levels, and all 0:02:15.840 --> 0:02:19.680 kinds of sensors to help watch four potential problems. They 0:02:19.760 --> 0:02:23.440 can feature paved paths and gates for pedestrian and vehicle 0:02:23.480 --> 0:02:29.880 traffic bridges, and even parks with landscaping and esthetic architectural features, 0:02:30.080 --> 0:02:32.280 you might not even realize that what you're standing on 0:02:32.560 --> 0:02:36.680 is part of a levee system. Levees often run in 0:02:36.720 --> 0:02:40.440 a long strip, sometimes for many miles, along a river, lake, 0:02:40.560 --> 0:02:44.720 or ocean. Just for example, levees along the Mississippi River 0:02:44.840 --> 0:02:47.560 may range from ten to twenty feet tall that's about 0:02:47.560 --> 0:02:51.440 three to seven meters. In Holland, they can top thirty 0:02:51.440 --> 0:02:55.680 feet that's ten meters, but there's no set height for levees. 0:02:55.919 --> 0:02:59.040 Their measurements vary according to storms that the area receives, 0:02:59.320 --> 0:03:02.000 even if those storms occur only once every hundred or 0:03:02.000 --> 0:03:06.840 one thousand years. Every levee system is different based on 0:03:06.919 --> 0:03:10.520 the particular conditions and risks in an area. They can 0:03:10.560 --> 0:03:14.360 incorporate salt water or freshwater marshes to help absorb flooding. 0:03:15.080 --> 0:03:18.880 Coastal systems especially may be helped by periodic beach renourishment 0:03:19.000 --> 0:03:22.440 to replace sand, soil, and rocks that are eroded during storms, 0:03:23.639 --> 0:03:26.520 and levee systems can be built in conjunction with dams 0:03:26.560 --> 0:03:30.280 to better manage a whole area's watershed. A living by 0:03:30.320 --> 0:03:33.240 the water provides humans with a number of advantages a 0:03:33.280 --> 0:03:39.160 fertile farmland, transportation, trade, and hydroelectric power. Levees allow humans 0:03:39.160 --> 0:03:42.840 to enjoy these assets with less fear of flooding. While 0:03:42.960 --> 0:03:45.720 strolling along the beach or enjoying a picnic by a riverbank. 0:03:45.880 --> 0:03:49.600 It's easy to forget the strength of water until floods 0:03:49.600 --> 0:03:53.760 and storms jar us to remember. In nineteen thirteen, the 0:03:53.800 --> 0:03:57.800 Ohio River and its tributaries flooded, submerging several cities and 0:03:57.880 --> 0:04:01.480 killing one thousand. In nineteen twenty seven, the Mississippi River 0:04:01.560 --> 0:04:04.760 swelled during several months of heavy rain, charging through a 0:04:04.800 --> 0:04:07.440 line of levees and flooding an area the size of Ireland, 0:04:07.720 --> 0:04:12.200 displacing hundreds of thousands of Southerners. In nineteen fifty three, 0:04:12.560 --> 0:04:15.680 the North Sea broke through netherlands ancient system of dikes 0:04:15.720 --> 0:04:21.880 and killed thousands. Through these and other disasters, our scientific 0:04:22.000 --> 0:04:26.320 understanding of waterways evolved. Engineers now operate with the base 0:04:26.400 --> 0:04:30.240 concept that water cannot be fully controlled, but can be 0:04:30.400 --> 0:04:36.080 mitigated through broad and interconnected flood risk management systems. But 0:04:36.320 --> 0:04:41.800 even with this understanding, disasters still happen. Back in two 0:04:41.839 --> 0:04:45.839 thousand and five, Hurricane Katrina breached New Orleans levees. Much 0:04:45.839 --> 0:04:49.440 of the city lies below sea level. Throughout history, low 0:04:49.520 --> 0:04:52.920 lying boggy areas have been pumped dry to create new land. 0:04:54.000 --> 0:04:56.719 Much of this reclaimed land has sunk as it dried out. 0:04:57.600 --> 0:05:00.479 The entire city now depends on the levees, along with 0:05:00.560 --> 0:05:05.120 massive pumping stations to keep the water out. Katrina flooded 0:05:05.240 --> 0:05:08.279 eighty percent of the city, killing some one thousand, six 0:05:08.360 --> 0:05:13.240 hundred people and displacing about two hundred thousand others. But 0:05:13.400 --> 0:05:17.240 how could this happen in a modern city. Investigations over 0:05:17.279 --> 0:05:21.960 the following decade pointed to a few major reasons. First, 0:05:22.120 --> 0:05:26.400 there was insufficient planning. New Orleans levee designs were based 0:05:26.440 --> 0:05:30.520 on an outdated study from nineteen sixty five. Engineers built 0:05:30.520 --> 0:05:32.440 the system with the goal of standing up to the 0:05:32.440 --> 0:05:37.159 worst storm possible in two hundred years. Unfortunately, the study 0:05:37.200 --> 0:05:42.440 greatly miscalculated how powerful potential storms could be. Second, the 0:05:42.480 --> 0:05:46.400 design was risky. New Orleans levees were built to sustain 0:05:46.440 --> 0:05:49.560 the city's growth, unlike the levees and neighboring areas, which 0:05:49.600 --> 0:05:53.480 were built to provide safety. As result, New Orleans levees 0:05:53.520 --> 0:05:58.120 were shorter and weaker. Third, the safety of the system 0:05:58.160 --> 0:06:02.440 was compromised by bureaucracy. No central agency was in charge 0:06:02.480 --> 0:06:06.400 of maintaining the levees. This task instead fell to several 0:06:06.440 --> 0:06:10.839 different private firms and government agencies, leading to communication problems 0:06:10.880 --> 0:06:15.279 and the breakdown of various upgrade projects. Fourth, there was 0:06:15.320 --> 0:06:20.160 poor maintenance. Levees require constant upkeep. As the land in 0:06:20.200 --> 0:06:24.800 New Orleans sinks, so do the levees. And Fifth, there 0:06:24.800 --> 0:06:29.640 were insufficient funds. The US Army Corps Engineers, which oversees 0:06:29.680 --> 0:06:32.280 the design and construction of levees, had been hit by 0:06:32.279 --> 0:06:36.560 budget cuts. This left the agency with fewer experienced engineers. 0:06:38.440 --> 0:06:41.080 As New Orleans rebuilt from the disaster, some of these 0:06:41.120 --> 0:06:45.279 concerns were addressed. The Army Corps Engineers designed a system 0:06:45.279 --> 0:06:48.400 of floodwalls and levees snaking three hundred and fifty miles 0:06:48.600 --> 0:06:52.200 that's five hundred and fifty kilometers through five parishes, at 0:06:52.200 --> 0:06:56.919 a cost of over fourteen billion dollars. However, that was 0:06:57.000 --> 0:07:00.360 now twenty years ago and maintenance is an ongoing issue. 0:07:00.480 --> 0:07:03.479 They estimate that it'll cost another billion dollars in upkeep 0:07:03.520 --> 0:07:06.320 over the next fifty years, and that kind of funding 0:07:06.520 --> 0:07:11.200 is frustratingly hard to come by. The Netherlands faced a 0:07:11.200 --> 0:07:15.320 similar situation following the flood in nineteen fifty three. In 0:07:15.360 --> 0:07:18.080 the decades that followed, engineers set out to build a 0:07:18.120 --> 0:07:21.840 new kind of barrier against the sea. They steadily replaced 0:07:21.880 --> 0:07:24.040 the old dike system which had been in place since 0:07:24.080 --> 0:07:27.880 the medieval ages, and created, weirdly enough, right around three 0:07:27.960 --> 0:07:30.640 hundred and fifty miles of what many consider the safest 0:07:30.720 --> 0:07:34.920 levee system in the world. They started by reevaluating their 0:07:35.040 --> 0:07:39.000 entire system in several key ways. They set out thinking 0:07:39.080 --> 0:07:43.679 long term, like really long term, new orleands. Old levees 0:07:43.680 --> 0:07:45.800 were built to with stand the strongest possible storm in 0:07:45.840 --> 0:07:50.320 two hundred years. Netherlands engineers designed a system strong enough 0:07:50.360 --> 0:07:53.000 to match the kind of catastrophic storm that only occurs 0:07:53.120 --> 0:07:58.320 once in ten thousand years. Also, instead of constructing increasingly 0:07:58.320 --> 0:08:02.080 bigger solid barriers like levees and flood walls, they sought 0:08:02.080 --> 0:08:05.800 to create better ways of absorbing floodwaters in marsh plains 0:08:05.960 --> 0:08:10.800 and specially constructed rivers. In some cases, this involved setting 0:08:10.880 --> 0:08:15.120 dikes farther back from the water. The engineers also developed 0:08:15.160 --> 0:08:19.600 tough synthetic textiles to better anchor earth than levees These 0:08:19.600 --> 0:08:23.720 prevent soil movement and water penetration. The New Lands Levee 0:08:23.760 --> 0:08:29.280 system began using this technology following Hurricane Katrina. The Netherlands 0:08:29.320 --> 0:08:33.400 also implemented more stringent and centralized control and maintenance of 0:08:33.440 --> 0:08:36.920 their dikes and now use automated surveillance systems to keep 0:08:36.960 --> 0:08:39.800 an eye on how their levees are holding up. They 0:08:39.840 --> 0:08:43.160 installed fiber, optic and electronic sensors in dike structures to 0:08:43.200 --> 0:08:47.160 report changes back to a central monitoring system. The several 0:08:47.160 --> 0:08:51.959 other systems monitor water pressure and water level. A major 0:08:52.080 --> 0:08:56.200 challenge in maintaining levee systems in urban areas is urban sprawl, 0:08:56.440 --> 0:09:01.280 which can place increased pressure on existing levee structures. Levees 0:09:01.320 --> 0:09:05.720 require regular maintenance, constant monitoring, and a long term appreciation 0:09:05.960 --> 0:09:10.640 for how rivers, oceans, and storms behave. When these are 0:09:10.640 --> 0:09:14.040 in place, communities can thrive safely along the beauty and 0:09:14.120 --> 0:09:18.360 convenience of coastal and riverside areas. It's when we fail 0:09:18.440 --> 0:09:26.760 to remember this that rivers and oceans become destroyers. Today's 0:09:26.760 --> 0:09:29.080 episode is based on the article what is a levee? 0:09:29.120 --> 0:09:31.920 On HowStuffWorks dot com, written by Marshall Brain and Robert 0:09:32.000 --> 0:09:35.040 Lamb brain Stuff is production of iHeartRadio in partnership with 0:09:35.080 --> 0:09:37.640 how stuffworks dot Com and is produced by Tyler Klang. 0:09:38.160 --> 0:09:41.280 Four more podcasts from my heart Radio. Visit the iHeartRadio app, 0:09:41.360 --> 0:09:44.200 Apple Podcasts, or wherever you listen to your favorite shows.