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<br />. <br /> <br />. <br /> <br />Review of the COE hydrologic determination uncovered several <br />problems with their work. The Lake Minnequa basin is <br />characterized by a lack of natural drainage channels. The basin <br />develops in the foothills southwest of Pueblo where it is drained <br />by several well defined drainage ditches. The natural channels <br />however disappear at an elevation of approximately 5000 feet <br />above sea level and the basin fans out to drain toward Pueblo. <br />The majority of the Lake Minnequa basin (85%) therefore, consists <br />of sheet flow runoff on flat slopes (1-1.5%), and no defined <br />drainage channels. Since TM-l utilized few if any basins which <br />are similiar in size or runoff characteristics to the Lake <br />Minnequa basin it is not appropriate to use TM-I for the lake <br />hydrologic determination. In addition when checking the COE <br />floodplain delineation downstream of the lake we were unable to <br />confirm the COE typical section and depth-discharge <br />relationships. It appeared to us that the COE overestimated the <br />capacity of the street network. Since the use of the TM-l to <br />analyze basins that are largely characterized by sheet flow, flat <br />slopes, and depression storage will yield disproportionately <br />large flows we feel that the COE overestimated the flooding <br />potential from Lake Minnequa. The COE work should therefore, be <br />replaced with more appropriate information for use in the Pueblo <br />Flood Insurance Report. <br /> <br />. <br /> <br />. <br /> <br />I. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />-3- <br /> <br />. <br />