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1 <br />1 <br />i7 <br />TABLE 2 <br />YO <br />ABOVE FORTIFICATION CREEK <br />1492 miz <br />a <br />Y1 <br />AT CRAIG GAGE (BELOW FORTIFICATION CR) <br />1750 mil <br />a <br />Y2 <br />BELOW WILLIAMS FORK <br />2241 mil <br />b <br />Y3 <br />BELOW MILK CR <br />2529 mil <br />c <br />Y4 <br />AT MAYBELL GAGE (BELOW LAY CREEK) <br />3410 miz <br />a <br />Y5 <br />BELOW SPRING CR <br />3520 miz <br />c <br />Y6 <br />ABOVE LITTLE SNAKE R <br />3796 miz <br />c <br />Y7 <br />BELOW LITTLE SNAKE R <br />7606 miz * <br />b <br />Y8 <br />DEERLODGE PARK GAGE <br />7660 miz <br />a <br />Sources of Drainage Areas <br />a. Determined from published information and USGS gage values <br />b. Determined from tributary USGS gage information combined with planimetering <br />c. Determined from planimetering <br />* The drainage area for the Little Snake gage location is at a point 9 miles upstream from the confluence with the Yampa <br />River. An additional 80 miz were measured between the gage location and the confluence. <br />Only one problem was encountered during the drainage area determinations. The drainage area <br />published by FEMA for the downstream limit of the study for the Craig Colorado area (215.0 mil) <br />was found to differ significantly from the value at the USGS gage location (1750 mi2). After a <br />careful review, including planimetering upstream of Craig to the Steamboat Springs gage and <br />downstream to the Maybell gage, the value at the gage location was selected as the most accurate. <br />It is not clear what the source of the FEMA drainage area was, but it was assumed to be in error. <br />Figure 4 shows the study reach and each of the hydrologic analysis points listed in Table 2. <br />2.5 Flood Characteristics <br />Major flooding in the Yampa River basin has been primarily the result of rapid snowmelt <br />beginning as early as late April. Snowmelt flooding can continue into early July. Flooding can <br />also occur from rainfall on snowmelt and from ice jams in late winter or early spring. Due to <br />the small areal extent and limited duration of thunderstorms, they do not typically constitute a <br />flood threat on streams as large as the Yampa River. They do, however, pose a problem for <br />some of the smaller tributaries in the basin. <br />7 <br />