Laserfiche WebLink
<br />hydraulic analyses utilized the U.S. Army Corps of Engineers HEC-2 <br />hydraulic computer model and were conducted in August 1986 and <br />September 1987. The hydraulic reanalyses modified the 100-year and <br />500-year flood boundaries and increased the base (lOO-year) flood <br />elevations (BFEs) along portions of the South Platte River by up to <br />5 feet. A floodway was not analyzed for this 2.3-mile reach <br />primarily due to the split flow situations along the South Platte's <br />floodplain. The Floodway Data Tables and Flood Profiles were <br />modified to reflect the revised flooding. <br /> <br />This revision also incorporates the Letter of Map Revision (LOMR) <br />issued on September 28, 1988, to reflect channel modifications and <br />lot grading through Third Creek Estates Subdivision downstream of <br />East 132nd Avenue, as shown on FIRM Panel s 0010, 0020, and 0050. <br />In support of this LOMR, Adams' County Development Review Section <br />submitted "as-built" drawings of cross sections, a topographic map <br />delineating the 100-year floodplain boundaries, and printouts of a <br />HEC-2 hydraulic analyses, all prepared by Alpha Engineering. Based <br />on these data the 100-year flood boundaries were revised to reflect <br />the channel modifications along a reach of Third Creek, <br />approximately 1,690 feet long, and located immediately downstream <br />of 132nd Avenue. <br /> <br />The LOMR issued on July 21, 1987 to reflect the completion of a <br />flood control project in the vicinity of Hidden Lakes Drainageway, <br />as shown on FIRM Panel 0155, was also incorporated. <br /> <br />In support of this LOMR the following data, developed by Hydro- <br />Triad, Ltd., were submitted: <br /> <br />. A report entitled "Hidden Lake Drainageway 100-Year Floodplain <br />Revisions," dated May 1986 <br /> <br />. "As-built" plans enti tled "Hidden Lake Drainageway Channel <br />Improvements," dated June 1985 <br /> <br />. "As-built" plans entitled "Hidden Lake Drainageway Planning <br />Study - Phase A Report - City of Arvada - Adams County," dated <br />June 1975 <br /> <br />. A report entitled "Major Drainageway Planning - Hidden Lake - <br />Bates Lake - Volume I - Phase B" dated November 1975 <br /> <br />. A report entitled "Major Drainageway Planning - Hidden Lakes - <br />Bates Lake - Volume III - Phase B." dated November 1975 <br /> <br />Based on these data, the 100-year flood boundaries were revised to <br />reflect approximately 0.8-mile of channel modifications along <br />Lowell Boulevard, located south of West 67th Avenue. <br /> <br />37 <br />