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complexes. These local levees, if adequately maintained, generally protect against more frequent lower level flood events, but they are of1:en ovenopped during higher floods if not adequately designed. Usually, floodgates and pumping stations are required for interior drainage and seepage, Both ga1:es and levees require periodic maintenance. Local levees sometimes fail without being overtopped because of poor design, improper material and/or construction practices, inadequate pumping facilities, or other reasons. Therefore, it is strongly recommended that all levees and floodwalls be designed and constructed under the supervision of qualified professional engineers, . Floodwalls are often added after buildings'\,or proper1:ies have experienced flooding one or more times and are generally used where space or other considerations preclude the use of levees. If designed properly, floodwalls are effective because they require little maintenance and ~an be easily i~spected, Disadvantages of this method include the inicial cost, keeping closure materials accessible, and training personnel to ensure timely closure. Generally, floodwalls are constructed from concrete or concrete blocks and have one or more passageways that are closed by gates. Occasionally, a structure will have~a floodwall incorporated into the architectural design. The use " of levees and floodwalls usually requires that a sump pump, system be installed to evacuate boch internal drainage and the underseepage that might occur, Excessive underseepage from improper design is a common problem in the use of these measures. Also, a problem with this concept of protection is that failure of che sys1:em either scructurally or by overtopping can result in damages as great as or greater than if no protection had been attempted. - 30