Levees has been used as a structural flood protection means for several thousand years. Its effect and effectiveness have been debated periodically, most recently during and after the 1993 Mississippi River flood. Based on hydraulic principles it can be shown that for a given flood levees raise the water stage in the leveed channel and upstream of it, it may slightly lower the water stage downstream. Methods for channel capacity determination and identification of low-capacity bottlenecks suitable for levee or channel improvement are also discussed. Effectiveness of levees is site- specific. Usually it is more effective to use levees in conjunction with other structural and nonstructural flood control measures.