Laserfiche WebLink
<br />Manning's On" value for the proposed wetland and spoil area was assumed to be the <br />same as the existing overbank On" value, For this alternative, it was assumed that the <br />excavated material would be placed in a 218 acre area located to the north of the <br />proposed wetland and within the project site, A 100-year floodplain run for the <br />proposed configuration was compared to the existing conditions 100-year floodplain <br />run, The results are shown in the table which follows, and show that the <br />.- backwateriwetland complex may increase the Missouri River 100-year water surface by <br />approximately 0,5 feet. The HEC-2 output file is included in this appendix, <br /> <br />e. Summary of Results <br /> <br />, The purpose of the previously described HEC-2 modeling effort was to identify any <br />impacts to the Missouri River existing 100-year floodplain, The existing 100-year flood <br />profile was assumed to be the water surface elevations computed by the existing <br />conditions HEC-2 model provided by the Corps, Water surface profiles computed by <br />subsequent proposed conditions HEC-2 models were compared against the existing <br />conditions results. In general, the proposed pilot channels and ultimate chute channel <br />have an insignificant effect on the Missouri River 100-year floodplain, The pilot <br />channels would cause a maximum water surface decrease of less than 0,5 foot. The <br />backwateriwetland complex would cause a maximum water surface increase of about <br />0,5 foot. The following table shows the results of the floodplain analyses, <br /> <br />~ <br /> <br />,. <br /> <br />.,( <br /> <br />. <br />