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<br />Elevating on piles <br /> <br />or columns <br /> <br />This method is frequently used where the dynamic forces of <br />wave action or floodwater velocity is severe, or where the water <br />surface can vary considerably. Structures built on piles are often <br />found in coastal areas and along river overbank areas and <br />lakeshores. One advantage to this method is that the flow of <br />floodwater is not restricted and impacts on flood storage <br />capacity are minimized. Also, open areas under the structure <br />can be used for parking or storage of materials that can be easily <br />moved. Even though the best time to flood proof is obviously <br />during initial construction, this method is often the most <br />practical for flood proofing existing structures as well. <br /> <br />Levees and floodwalls <br /> <br />Levees considered in this report are those built around single <br />homes, small subdivisions, and individual industrial complexes. <br />These local levees, if adequately maintained, protect against <br />more frequent lower level flood events; however, they are often <br />overtopped during higher floods. Usually, pumps are required <br />to handle interior drainage and seepage. Both floodgates and <br />levees require periodic maintenance. Since local levees <br />sometimes fail without being overtopped because of poor <br />design, improper material and/ or construction practices, poor <br />maintenance, inadequate pumping facilities, and related <br />reasons, it is strongly recommended that all levees, as well as <br />flood walls, be designed and constructed under the supervision <br />of qualified professional engineers. Failure of levees protecting <br />major urban and industrial areas can result in catastrophic <br />losses. <br /> <br />Floodwalls are often added after a building or properties have <br />experienced flooding one or more times and generally are used <br />where space or other considerations preclude the use of levees. <br />If designed properly, floodwalls are effective because they <br />require little maintenance and can be easily inspected. The main <br />problems with this method are keeping closure materials <br />accessible and in good operating order and training personnel to <br />assure timely closure. Generally, flood walls are constructed <br />from concrete or concrete blocks and have one or more <br /> <br />7 <br />