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~lope is approximately 109 feet per mile in the ~~tershed, and only 63 feet per ~ile within the study r98Cn. Strea~bad ele- vations within ths study reach vary from approximately 4,7G8 feet at the ~outh to 4,868 feet at Mile 2.52. flood plain widths would vary from less than 50 feet juet below State Highway 96 (Thatcher Avenue) during on lnter~ediete Regional flood to a maxi- mum of 400 feet at the Denver and Rio Grands Western Railroad bridgs during a Standard Project flood, excluding the Arkansas Rivar flood plein area. Pertinent drainag<< areas of Goodnight Arroyo ere given in Table 5. Mouth 0.00 5.9 The Colorado Stete Hi9h~a~ 96 (Thatcher Avenue) bridge. Bessemer Ditch_A~a Drive crossing, and Red Creek Road bridge are located at Milae 0.45, 0.51, and 1.66, respectivel~. The Denver and Rio ~randa ~estern R~i~roed crosses the ~rroyo Over an Be-foot 5-span structure that is skewed 10 de~ grees.to the normal direction of flow. The Standard Project flood would overflow the roadway 1 foot deep, but the Intermedi_ ate Regional flood would not reach the roadwa~. Head losses would be 5.7 feet d~ring the Standard Project flOOd, and 4.9 feet during the Intermediate Regionel flood. Colorado State Highway 96, extending ~est~ard on Thatcher Avenue, crosses the streambed Over a 28_foot wide by 16- foot h1gh concrete.aroh bridge. The floor of the bridge would not ba overtopped by either the Standard Project or the Internediate Regional flood. Head losses at the bridge would bs 13.1 feet and 10.6 feet. respectively, for the Standard Project flood end Inter- medi~te Regional flood. The Ses"emer Ditch-Ac~a Drive arroyo dra1nagewa~, an oval-shaped cou"g"tad msbl culvert, 17.5,feet high and :5 fs~t ~ids, ia Skewed 78 degrees. Neither the ditch nor the drive will ~e overtopped by the Standard Project or Intermediate Regional flood. The head losses would be lB.8 faet durinq the 5tenda=d Project flood, and 15.5 feet during the lnter~sdiata Regional flood. The Red Creek Road bridge Over Goodnight Arroyo is a 22_foot aingle-epan wood structura that is skewed 40 degrees. The Standard Project flocd would overtop the floor by C.2 feet. while the IntermedL.te Regioncl nOCd ~oLJld not reach the f;'oor. Kead lossas ct the bridge during the Standard Project flocd end intermedi~te Regional flood wo~ld be 3.2 feet and 3.3 feet. res_ pectively. TABLE 5 DRAINAGE AREAS IN WATERSHED Of GOODNIGHT ARROYO Location Nile Above Mouth - Drainage Area C.40niles upstrecm of Red Creek Road. 2,07 5.1 Devalopments in the flood Plain Pl"t~ 7 5ho,"" the flOOd pl"ins of Goodnight A=royo for the re~ch covered by this ruport. This strearn Ch.nnol lies jU!t outside Pueblo's existing wBetern boundary and the region is presently onl~ sparsely developed. The city of Pueblo hae maintai~ed ~n open dump upstream of Bessemer Ditch that constricts the ch~nnel somewhat. Progras~ivB urbanization in the araa is con"iderad probable within tho next five year.. Br1dce3 Acro33 the 5trea~ There are three vehicular bridges and one railroad brid~e across Goodnight Arroyo in the 2.5 mile study reach. Photographs of the bridges ara sho~n 1n figures 7 ~nd B. The Denver and Rio Grande We~tern Railroad bridge is j~et upstream of the Goodnight Arroyo-Ark~n"e~ River confluence ct ~ile 0.18. Table 6 11sts pertinent elevations for the bridges. and rela~es their unde:=lcar~nce elevation to the crest of the !nt~rmediate Regional ,"ood. A di"cus~1on of the v~ri~~lA " "