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<br />III. <br /> <br />GENI;RAL STUDY AEEA DI::3CRIP'l.'ION <br /> <br />D::ainage Basin Characteristics <br /> <br />Tne Westerly Creek drainage t)asin is J'ul ty urbanized in the <br />lower reaches and is rapidly approachj.ncT a state of full <br />development in the upper n,aches. This tatter development <br />is characterized by thE' now typical nE'W construction in <br />the Denver area; i.e., townhOusE:S, condominiums, apartmE~nts, <br />motels, larere shopping complexes, st:rE!eL", parkiner areas, <br />and high,vays. This construction re,;ult,', in an increase of <br />.impervious surfaces, which 1.rt turn causC';:; increases in t:he <br />quantity and rate of runoff of storm"la.tc:c flows .-- flows <br />which in large measure formEe:i'ly seep'''cl j,nto the ground and <br />for which the rates of runoff were fonne:~ly much lower. <br />Flooding then results because of thE! lack of or inadequacy <br />of existing conveyance facilities in the lower reaches of <br />the basin. <br /> <br />Westerly Creek traverses a nllffiber of separate jurisdic::ions: <br />1:he City of Aurora" Lmny Ai!: ForCeIJase" thEe Ci t Y and <br />County of Denver, and Stapleton Int's,;~natj.onal Airport, <br />as wall as small unincorporated area~ of Arapahoe County. <br /> <br />The ,'1esterly Creek drainage J:lasin (:)rawi i:ler No. 2 of Volume <br />II) is a crescent-shaped area drainincJ in a nort:hwest.-to-. <br />north direction to its confluence with Sand Creek, a right- <br />bank tributary of t:he South plat te :':.i ver. 'rhe headwat:ers <br />of t'1e watershed rise on a low roll:Ll<j cLi.vide between thE' <br />Cherry creek and West Toll Gate Creek drainacjE! areas" The <br />basi:1 is about 8.5 miles long', 3 milE'S Hide at its widest <br />point, and consists of about 18 square miles of highly <br />developed areas. E'rom the headwate:cs to the confluence <br />with Sand Creek, the total fall in tt~ watershed is 425 <br />feet, or an average s lope of O. <) percent" 'rhus t:he water.- <br />shed tends to have a rapid response too ~:t:orm even.ts in <br />both individual local subareas and in the basin as a whole. <br />The basin at the present time conta:,n" a"'proximately 900 <br />acre--feet of detent,ion storage, 80 pcrcer: t of which is in <br />man-made storm detention facilit::Les of varying adequacies <br />to control flooding. <br /> <br />As shown on Drawing No.2, the basin abO've Lowry Air <br />Force Base is bisected by the Uighlire Canal, a man-made <br />leveed channel constructed in the late 1800's to carry <br />irrieration water for municipal, industrial, and agricultur- <br />al u~;e in tI'le Denver area. FOrnl(;rly r the canal acted as a <br />drainage divide effectively shuttiner off contributions of <br />flow from the upstream to the dmmstr:ean' portions of the <br />watershed.. 'rhis is no lonoer tL1C bccau:;e of the increased <br />and increasiner urbanizaLion, of L1C UPI'2r watershed and thE! <br />extremely limited capacity of the canal under storm flow <br /> <br />--7- <br />