Levees are earthen embankments whose primary purpose is to furnish flood protection from seasonal high water for a few days or weeks a year. Levees are broadly classified as either urban or agricultural because of the different requirements for each. Urban levees provide protection from flooding in communities; including their industrial, commercial, and residential facilities. Agricultural levees provide protection from flooding in lands used for agricultural purposes. There are five main types of levees:
- Mainline and Tributary levees: generally parallel the main channel and/or its tributaries.
- Ring levees: completely encircle or "ring" an area from all directions.
- Setback levees : generally built as a backup to an existing levee that has become endangered due to such actions as river migration.
- Sublevees: constructed for the purpose of underseepage control. Sublevees encircle areas landward of the main levee that are flooded, generally by capturing seepage water, during high-water stages thus counterbalancing the hydrostatic pressures beneath the top stratum.
- Spur levees: project from the main levee and provide protection to the main levee by directing erosive river currents riverward.
On the main stem of the Mississippi River, there are approximately 1,602 miles of levee in place.