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<br />. <br /> <br />. <br /> <br />. <br /> <br />0022J9 <br /> <br />CHAPTER III <br /> <br />DRAFT <br />August 30, 1989 <br /> <br />RECOMMENDATIONS ON MEANS TO RESTORE AND MAINTAIN THE FLOODWAY <br />INCLUDING, BUT NOT LIMITED TO, SPECIFIC INSTANCES WHERE LAND <br />TRANSFERS OR RELOCATIONS, OR OTHER CHANGES IN LAND <br />MANAGEMENT, MIGHT BEST EFFECT THE PURPOSES OF THE COLORADO <br />RIVER FLOODWAY PROTECTION ACT. <br /> <br />The Colorado River Floodway Protection Act calls for the <br />establishment of a federally-declared Floodway from Davis Dam <br />to the Southerly International Boundary between the United <br />StateS of America and the Republic of Mexico. It is to <br />accommodate either a one-in-one hundred year river flow <br />consisting of controlled releases and tributary inflow, or a <br />flow of forty thousand cubic feet per second, whichever is <br />greater. The forty thousand cubic feet per second flow <br />corresponds to the long-standing target maximum flood control <br />release Objective of Hoover Dam which was established with <br />the Dam closure in 1935. The one-in-one hundred year <br />frequency flow is the standard level of protection that has <br />been adopted in the administration of the National Flood <br />Insurance Act. <br /> <br />For the most part, the boundaries of the Colorado River <br />Floodway, as provided in the Act, lie within the existing <br />main river channel. The most notable exceptions are below <br />Imperial Dam. The adjacent area, defined in the <br />determination of the Floodway boundaries as the Colorado <br />River Floodway Fringe, is the area subject to inundation by <br />floods of varying magnitudes up to and including the Floodway <br />flow but which is not required for safe conveyance of the <br />Floodway flow and is not included in the computation of the <br />Colorado River Floodway elevation. The Floodway Fringe <br />varies from being within the existing main river channel to <br />encompassing large adjacent areas, again principally below <br />Imperial Dam. <br /> <br />To restore and maintain an effective Floodway will <br />require coordinated implementation efforts by federal, state, <br />tribal, and local agencies and the establishment of a long- <br />term coordinated Floodway maintenance program with defined <br />areas of responsibili ties. The effective implementation of <br />the Floodway will occur principally through the adoption of <br />amended or new local and tr ibal flood plain management <br />regulations and improved flood plain management planning and <br /> <br />III-l <br />