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R~dS Across the Str~m Goldsmith GulCh has 17 existing rood crossIngs. In addl- t10n, the planned Interstate 225 cross1ng structure was Included In the study to determine the effects of obstructions on flood flows. There are no rallrood crosslogs. All of the roadway structures are pipe or box culverts, eIther of corrugated metal or of reinforced concrete. Midway betweeo East Yale Avenue and East Hampden Avenue, GoldsmIth Gulch Is crossed by the Hlghlloe Canal with a reloforced concrete pipe structure provided under the canal. Near the upstream eod of the drainage area, between Berry Avenue and Orchard Road, there Is a small earthen dam across the str~m with a reinforced concrete pIpe conduit. There Is about 1,730 feet of continuous under- ground reloforced concrete box culvert from Just downstream of East II!ff Avenue to a polot 230 feet downstream from East Evans Avenue. 1111 of the structures except Cherry Creek Drive and Interstate 225 are too small to pass the Intermediate Regional Flood without OVer- flow of the road embankmeots. Emben~nt overflows occur either at the structure or at some low point of the roadway approachIng the structure. SouthYosarnlte Street and Berry IIvenue are all raised aoout 6 feet at>ovethefloodplaln. Thelnterstate225arnbankmeot,asplanoed, will rise to about 19feetabovethefloo<lplaln. Theeftox:tsof the road emban~nts on stream flow profIles durlog large floods are shown graphIcally on the "Profile" plates for GoldsmiTh Gulch. Buildings 00 the flood plain also obstruct flood flows and can result 10 a genera! rise In flood depths. lXJTCHCREEK,LlLLEYGULCH,ANOCOONCREEK-GROIJP2 Stream-crosslng data on GoldsmIth Gulch Is shown In the Reference Point tabulations on pages 32 to 38. The relationships of the culverts to tho IntermedIate Regional and Standard Project Ftood~ are shown graphlcalty on the Profiles. STream and Valley Characteristics Dutch Creek drains <l 15 square mile area on the left bank of the South PI<ltte River southwest of Denver. The dralnaga basin Is abouT II miles long and 2.5 miles across the widest portIo n. The haadw<lters are In the front range In Jefferson County. Duteh Creek flows eastward across largely undeveloped high plains, eotering Arapahoo County aoout 1.5 miles upstream from Its nW:>lrth at the South Platte River. Lilley Gulch and Coon Creek are ~Jor tributaries of Dutch Creek, entering That stream from the left b<lnk 2.4 and 1.7 miles, respectively, upstrellm from the mouth. Lilley Gulch drains 2.92 s~uare mIles and Cooo Creek 4.69 squ<lre miles. The study reaCh for Dutch Creek extends from 1ts mouth to The Hogback 9 miles upstream. Lilley Gulch was studIed from Its mouthtO<lsmallreservolronemlleupstraarnfromSouthCarrStrect. The study reach for Coon Creek eXTends from the mouth to a small reservoir 0.63 miles upstream from South Carr Street. The three stre~ms have simIlar chanoel characterIstics In th<lt they <lre mostly In their natur<ll state, somewhat sinuous. and w1th tho ox~cptlo~ of COO~ Cr~~k, ch~nnAI ~Io~~ hACQmA flatter In the downstream direction. The flood plains "re rerrow but wIden sl ightly 10 the downstre;J'" direction. The floC<! plain chara,=,t""rl~- tIcs chaoge abruptly through the Columbt...... Couotry Club area. At ObstructIons to Flood FlowS Roads across the flood plain obstruct the flows of large floods and cause the flood depths to rise On the upstream side of tha roadways until the roadways are overtopped. Because of the steepness of the Goldsmith Gulch streambed, the Increased st<lges would occur only <l short distance upstream of the road crossings. Mo~tof the road emban~otsare fills less than 2 feet high above the flood pl<lln, although some embankments are considerably higher and produce large obstructions. Ct>....ry Creek DrIve, Bellevlaw Road, " "