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<br />Coordination with neighboring flood plain"/ <br />management programs; <br /> <br />Prohibition of any alteration or relocation of a~ <br />watercourse, except as part of an overall <br />drainage basin plan, to ensure that the flood <br />carrying capacity within the altered or re- <br />located portion of the watercourse is maintained; <br /> <br />Requirement to raise the minimum elevation for./ <br />all new construction and substantial <br />improvements within the Colorado River Floodway <br />Fringe area to be greater than the required one <br />foot above the Floodway elevation to provide an <br />added margin of safety against floods having a X <br />magnitude greater than the Floodway design flow; ~~ <br />vI <br />" <br />Requirement of coordination and consistency e~ <br />between federal, state, tribal, regional and <br />local comprehensive plans and flood plain <br />management programs; <br /> <br />prohibition, within the Floodway or Floodway/ <br />Fringe area, of facilities in which hazardous <br />substances are utilized, manufactured, or <br />stored; <br /> <br />14. Preventive action in the Floodway Fringe area,; <br />including setbacks and the relocation of <br />structures located in the path of flood-related <br />erosion. <br /> <br />002748 <br /> <br />. <br /> <br />10. <br /> <br />11. <br /> <br />12. <br /> <br />13. <br /> <br />. <br /> <br />IX. ISSUE <br /> <br />9. <br /> <br />Potential areas of high ground water levels associated ~ <br />with the Floodway elevation flow. <br /> <br />DISCUSSION <br /> <br />Under normal river flows, when reservoir releases are <br />limited to meeting only downstream water needs, the ground <br />water hydraulic gradients from lands along the river are <br />generally towards the river, with ground water basins <br />discharging water to the river. There are areas with <br />relatively shallow depths to ground water along the river. <br />In these areas, at the Floodway elevation flow, or even <br />lesser flows in excess of downstream water needs, the <br />increase in river elevation would either reverse the ground <br />water gradient, with the river discharging water to the <br /> <br />. <br /> <br />III-19 <br />