The United States’ levees stretch out for more than 100,000 miles, with the federal government operating around 2,100 miles of the system. The Congressional Research Service states that an estimated 22 percent of counties across the U.S., which represent about half of the population in the country, contain levees.
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How Levees Work
Levees are either artificial or natural dikes or embankments. These are essentially walls meant to prevent floodwater from flowing over certain areas. Levees contain the water for the prevention of floods or to increase the amount of land that can be used for human or animal habitation. Natural levees usually consist of earth or soil that has been impacted to ensure integrity, while artificial levees may be constructed using wood, plastic, metal and sandbags.
One of the key considerations that engineers focus on in the design of levees is how the embankment will remain anchored to the soil. Usually, plants, trees and grass like Bermuda grass are planted to help reinforce the levee boundaries.
Levees must be built well to withstand high pressure from water, particularly at areas that lead downstream. Too much pressure could cause the levee to break. This is particularly true for levees where water flow is confined to a small area. The confinement and the size of the area causes an increase in pressure downstream, which makes controlling flood water more difficult in case the levee breaks.
Federal Requirements for the Construction of Levees
Certain federal regulations are in place to ensure the proper construction of levees and the safety of the surrounding areas, particularly from flood. The designer of the levee must carefully consider how it would affect the flow of floodwater before construction. For example, engineers must consider if the levee would alter, impede or redirect the natural flow of the water, or if it would increase the speed of the water flow. They should also consider if the increase in speed could be managed.
Standards are also in place to ensure that levees are stable. Individual levees built for residential use, for example, should have a maximum height of six feet. Requirements for fill materials should also be met. Fat clay, if used, must be with high plasticity while lean clay must have low plasticity. If sand or clayey sand is used, the material should have over 12 percent fines.
The Quality of Levees in the U.S.
About 70 percent of the levees in the U.S. may not be able to offer enough protection from flood water. Furthermore, an estimated 20,350 miles of these levees have not been accredited. Around 20,000 miles of levees are in danger of breaking and causing flooding. The current lengths of levees that run across the U.S. can also be changed by corrosion of closures, natural erosion and animal burrows and similar activities. They can also be altered when pumps become worn out.
Where Climate Change is a Factor
Among the different natural disasters that occur in the U.S., floods are the most common. In 2015 alone, the average insurance policy premium for flood paid for by Americans was nearly $700. Climate change also plays a key role in the increase in flood incidents. Before 1900, there was only a 1 to 2.5 mm rise in sea level per year. After the advent of modern industrialization, the figure rose slightly at 3 mm a year. In 100 to 300 years, experts believe sea levels will rise by a staggering 5 feet. This much water will keep about 88 percent of New Orleans submerged. Already, cities in the East Coast have experienced an increase in flooding.
How to Address the Issue
Levees play a critical role in the containment, control and management of floodwater for the protection of the environment. Hence, their construction, maintenance and operation must be performed by state, private and local entities. Government agencies at the federal level already provide emergency response, hazard mitigation support, crop insurance and flood control dams.
In 2013, the American Infrastructure Report Card gave a grade of D- for the country’s levee system. A grade of D indicates that the infrastructure is in poor condition and at risk. It also indicates that most of the system are below standard, with a large portion showing significant deterioration. There is also serious concern regarding the capacity and condition of the system, which has a high possibility of failure.
To repair the system and restore its safety and stability, an estimated cost of $100 billion is required. Immediate and effective solutions are necessary to ensure that levees in the U.S. are improved. To illustrate its significance, the nation’s system has prevented over $141 billion worth of flood damage in 2011 alone.
One of the most common problems that levee construction faces is that some construction and engineering firms tend to decline or avoid levee work due to the uncertainty regarding the risk of liability for providing this type of service. There are also no quality regulations on both the state and federal levels to standardize the construction and maintenance of levees, which may explain in part why U.S. levees are in such a poor state.
Programs for National Inspection of Levees
The USACE or United States Army Corps of Engineers has a Safety Program that conducts periodic and routine inspections of levees. Routine inspections are conducted once every year, allowing engineers to inspect the procedures of maintenance and operation of a levee’s system visually. There are 3 inspection levels of ratings used for inspection. These are: Acceptable, Minimally Acceptable, and Unacceptable. The Safety Program performs inspections and assessments of 2,500 levee systems, which is equal to only 10 percent of all the levees at national level across the U.S.
There are currently three factors that contribute to the quality of the levee system in the United States: authority, lack of controlled or regulated ownership, and climate change. Addressing these three issues will expedite the process to identify and find solutions to the current problem, and implement the necessary means to prevent, or at least minimize, future problems. The dismal state that U.S. levees are in today requires immediate action from the nation’s civil engineers who must design high-quality and cost-effective levee systems.
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