How does a levee system work?
"Non-Engineer" Answer: A levee is designed to hold back rising storm/flood waters.
Explanation: Artificial levees are constructed out of concrete, steel, and/or compacted earth. Levees are typically wider at their base and taper to a smaller, level surface at the top. Water pressure is lightest at the water’s surface and increases as you get deeper. Therefore, to hold back the immense pressures generated by rising waters, a substantially wide levee base is required. In essence, as the water pressure increases so must the levee wall thickness. Designers must carefully consider just how high the water level may rise and determine which type of levee construction is best suited to contain these dangerous conditions.
Most levees fail due to water overtopping them or when water passes underneath the levee foundations. Undermining the levee foundation can cause the levee wall to shift and result in a catastrophic sudden breaching of the levee wall. A breach releases highly pressurized water that can move houses off of their foundations. When flood waters threaten to overflow the levee walls, sandbags can be stacked atop of the levee’s level top to provide additional flood protection. When sandbags are placed on top of an existing levee, it is known as a cradge.
Commentary: The United States Army Corps of Engineers is the Federal agency responsible for levee design and construction. The USACE has been involved in many projects such as the Panama Canal, the Manhattan Project, construction of the Pentagon, and restoration of the Everglades. The Corps also owns and operates more than 600 dams.
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