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<br />Dolores River <br /> <br />documen1;ed in a USBR memorandum (Appendix A). Their position has <br />not changed. Therefore, the Ilwith-'projectll model allowed. <br />floodin9 in the right overbank. <br /> <br />Thu results of the Ilwith-projHct" model, shown on the <br />summary table below, indicate only a moderate rise of 1(2 'to 1 <br />foot at most cross sections through the study reach. The data <br />indicatH that flanking a new levee a.t .the upstream end would not <br />be a problem as long as any levee improvements are tied to high <br />ground :at Highway 145). Also, thE! water surface rise upstream <br />and downstream of any levee improvHments would be minimal because <br />of the Hxtensive overbank flood plain upstream end and the large <br />reservo:,r at the downstream end. The HEC--2 file is included as <br />IlNEWDOLli.OUTIl in Appendix B. <br /> <br />Tahle 1 lists the following information for each cross <br />section (starting at the downstream end): (1) cross section <br />number ilnd corresponding FEMA lettE!r designation (where <br />applicahle); (2) 100-year water surface as identified in the <br />Flood Insurance(Flood Hazard Informati.on Reports; (3, 4, 5, and <br />6) 10-, 50, 100-, and 500-year watE!r-surface elevations under <br />existin9 conditions; (7) 100-year water surface using the higher <br />Ilnll values; and (8) 100-year water surface under encroached or <br />Ilwith-pl:ojectll conditions. <br /> <br />FLOOD PIlOBLEM AREAS <br /> <br />As indicated in Columns 2 and 3 of Table 1, the water- <br />surface profile did not change subst:antially even when full <br />considel:ation was given to the levee. i.mprovements. with only a <br />few smaIl exceptions, the entire Town of Dolores would be <br />inundatHd by a 2 percent chance (50-'year) or greater flood. (The <br />50-year flood would cover approximately the same area as the 100- <br />year flood shown on Attachment 2 but, to a slightly shallower <br />depth.) Flooding would begin with about a 3 percent chance (33- <br />year, 10,000 cfs) flood event. Al1:hough overbank flood <br />velocit:les (the speed at which the water would go through town) <br />would not be very high for the mos1: part, the 1 percent chance <br />(lOO-yeilr) flood event would average about 2 feet in depth over <br />much of the flood plain. For these reasons, it is import.ant that <br />the town give consideration to the flood mitigation measures <br />describHd below. <br /> <br />7 <br />