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I I I ] I I I I I I I I I j I 3 , i 1 Discharge Profiles T~bles 1 and 2 summarize discharge profiles computed for several locatioos along the pioneer Ditch for the Sand Creek watersheds and Pawnee OverflOwS. The reader is referred to Ffgure8 for the location of each reacll. Thepeak discharges summarized in Tables 1 and? are for existing conditions. Data furnished by the City Planner indicate that a miljor development surge is not likely in the Sterling area for the next 20 years. Accordingly.thedis- charge profiles also reflect flooding potential for the forseeable future. The cumulative areas of developed and undeveloped watersheds are also shown forCOIIIparison. The discharges in Table 1 areesti~tesofimportedwater fromtne Pawnee overflow which j1reatly exceedS tile amount of water generated from tile upstream area tributary to the Pioneer Ditch between RiversideCernetery a~d H;~hwJY 14. ^n examination of the flood history has shown that the time to peak for Pawnee Creek at U.S. Highway 6 was 12 hours during the 1965 fJOOd(Matthai, 1969 and Sterling Journal Advocate: June 15, 1955). An additional 3 or more hours lapsed before flood waters reached the Pawnee Overflow. Giventllis la9 time for tile Jilrger flood events. itis seen that peak flows from wiltersheds tributary to the Pioneer Ditch are likely to have receded prior to the occurrence of Pawnee Creek overflows. Given this assumption. and independent occurrence of Pawnee and Sand Creek floods.100- yeilr flood peaks along the Pioneer Ditch vary from 5,000 c.f.s. between the overflow and Highway 14; 5.352 c.f.s. at the Sand Creek confluence; 6,483 c.f.s. at North 7th Avenue; and 5.880 c.f.s. at Highway 138. Aqaln. these pedks above are !Ienerated as the result of a flood occurrence on theS and Creek watersheds tributary to flioneer ditch. They do not include flawnee overflows. For e'"ergency planning. it sholll::! !:c assu...ed that ~ Sand rrf'I'k flood will peak within about 4 hours from the onset of heavy rainfall. This cOlllpdreswitha lag time ofapproxilnate1y 15 hours for a P<lwneeOverfl ow floOd to peak at Sterliny. .. I I I I I I I , -, I i! ~ ~ " w > 0 I w w = ~ - ~ I w " ~ Q W ~ ~ ~ ~ I w ~ - ~ ~ ~ I w w " " = u I ~ - 0 I I I I I I ~ \ I " " , . I . > w . - > ~ M . - r ~ - ~ ".\i,' ~ > " " > < . , . " . , " < . . = . , ~ , . w < r < " ~ 1.~ ~ ~ - 0 - = L = = 0 z ,. g 0 0 0 0 0 0 0 0 0 0 0 0 g 0 0 0 0 0 0 0 0 0 0 0 0 0 ~ - - - - - - - - - - - - - - - - - - 0 0 0 0 0 0 g 0 0 0 0 8 0 0 0 0 0 8 0 - 0 0 5l 0 5l 0 0 ~ ~ ~ ~ ~ ~ ~ - , 0 0 0 0 g 0 0 0 0 0 0 0 0 0 0 0 0 0 ~ . . . . . . ~ . . - " N " " N N N " , . -- ~ . - 0 - ~ ~ 0 ~ i!l g g 0 0 0 , N W ~ ~ w 0 w w = = = " - ~ --.... , . ,-.- _'_h_. - -~---- . . . . C-\ ~ " ~ 0 ~ 0 0 0 0 0 N .W " ~ " 0 0 0 ~ < - M ."': w w ~ 0 - N N ~ - - - - - . . .~~--- .._~--~.- n..... .--.--- 0 - 0 0 ~ 0 0 0 0 0 ~ w ~ ~ , 0 ~ 0 0 ~ - . . . ~ ~ , w = _..n - . N W . , , , ~ w 0 > w 0 w , ~ N 0 ~ , . , ~ N - " w , = w ~ < M M M M M M 0 ~...N - w ~ ~ ~ ~ ~ 0 W N , . . . - . . . . . 0 . , 0"- > , . . , , , , ~<~ . - - - 0 ~ -- z , , . , , , 0 g~ ~~ ~ . - " M 00 00 00 . . . , . , M~ ~M MU . N_ -- . > ~ ~ ~ _0 00 00 " -- -- ~u -- -- -- -, 15 . ~ - ~ " . > o . . . , . . < - ~ . ~ z o < '- " o < . > . . ~ o o - - . . . " u ~ < . ~ - -,