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<br /> <br />breakthrough and toe failures. <br /> <br />Flashboards are very susceptible to wave erosion, particularly <br />if waves break over the top of the structure. The backfill must be <br />protected from erosion with sandbags and/or poly to maintain the <br />integrity of the flashboard structure if wave action is a problem. <br /> <br />The materials required to construct flashboards can be <br />relatively expensive. Furthermore, the demand for some materials <br />may outstrip their availability in even moderate flood fights. If the <br />flashboard is subject to extended high water conditions, the <br />deterioration and warping of the wood can become a significant <br />problem. This problem can be reduced through the use of marine <br />grade materials, but this will also significantly increase the cost of <br />the project. <br /> <br />Notes <br /> <br />Mudbox Capping <br /> <br />Advantages: <br /> <br />..j Can be built up to 6 feet in height <br />..j Useful on narrow crown levees <br />..j Relatively simple design <br /> <br />Disadvantages <br /> <br />-~-,-,-~------------- ---_...--- -. --- - -----~- <br />..j Very costly to construct <br />..j Requires large quantities of lumber <br />..j Very labor intensive <br /> <br />-- <br /> <br />In capping to a height greater than 3 feet, or in capping a <br />narrow crown levee, mudboxes may be used. This method <br />involves constructing a wooden box near the river edge of the <br />levee crown and filling the box with tamped earth or clay fill. The <br />box should never be filled with sacks or sandbags. If possible, the <br />width of the box should be twice the height of the fill. <br /> <br />The construction of a mudbox is both material and labor <br />intensive. On narrow crowns, it may be necessary to haul fill <br /> <br />Page4-8 <br />