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I I I I I I I I I I I I I I I I I I I TABLE 2 ......................................... ......................................... ......................................... ......................................... :::::H:.":.YI):.:.::::.:':R;i.:.:'::Q:.:-:.:L.:.::::OO:.:..:::':-:.}:.:.C:::.:.::::::::: n.. . ... .... :;::::", :;';;::>.: :-::.-':-:,:::",:: ::}}:: ............................... ........ ........................................ ...................................... . .nriti:TT'. ~~~~~i-: Q;J,:J,.~: i:: :::::::::::::: ~:~:~::: :::::::::::::::::::.:.: ...................... ......-............................. .-..-.............................. ........................".......... .................................... .................................... .................................... ..::.U....:n:;;i!:;IN.....A.....G...E............. :<:::: ::~ :.:-::-.<,::' .':>> .........................,.......... .................................... .................................... .l'\,~^(Q.A-.).........i .............................. . YO Yl Y2 Y3 Y4 Y5 Y6 Y7 Y8 1492 mi2 1750 mF 2241 mF 2529 mF 3410 mF 3520 mi2 3796 mF ABOVE FORTIFICATION CREEK AT CRAIG GAGE (BELOW FORTIFICATION CR) BELOW WILLIAMS FORK BELOW MILK CR AT MAYBELL GAGE (BELOW LAY CREEK) BELOW SPRING CR ABOVE LITI1.E SNAKE R BELOW LITI1.E SNAKE R DEERLODGE PARK GAGE 7606 mi2 · 7660 mi2 Sources of Drainage Areas a. Determined from published information and USGS gage values b. Determined from tributary USGS gage information combined with planimetering c. Determined from planimetering . a a b c a c c b a * The drainage area for the Little Snake gage location is at a point 9 miles upstream from the confluence with the Yampa River. An additional 80 mi2 were measured between the gage location and the confluence. Only one problem was encountered during the drainage area determinations. The drainage area published by FEMA for the downstream limit of the study for the Craig Colorado area (2150 mi2) was found to differ significantly from the value at the USGS gage location (1750 me). After a careful review, including planimetering upstream of Craig to the Steamboat Springs gage and downstream to the Maybell gage, the value at the gage location was selected as the most accurate. It is not clear what the source of the FEMA drainage area was, but it was assumed to be in error. Figure 4 shows the study reach and each of the hydrologic analysis points listed in Table 2. 2.5 Flood Characteristics Major flooding in the Yampa River basin has been primarily the result of rapid snowmelt beginning as early as late April. Snowmelt flooding can continue into early July. Flooding can also occur from rainfall on snowmelt and from ice jams in late winter or early spring. Due to the small areal extent and limited duration of thunderstorms, they do not typically constitute a flood threat on streams as large as the Yampa River. They do, however, pose a problem for some of the smaller tributaries in the basin. 7