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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br /> <br /> <br />TABLE 2 <br /> <br /> <br />:~r~~~gl~...... <br /> <br />Gl <br />G2 <br />G3 <br />G4 <br /> <br />.",,,., "_',_n'_',""'_,'" "," <br />\~~~?~.! <br />.AWlfl... Q;i;fl.') <br /> <br />562& mi' <br />6760 mi' <br />699& mi' <br /> <br />DELTA GAGE <br />BELOW UNCOMPAHGRE RIVER <br />BELOW ROUBIDEAU CR <br />BELOW ESCALANTE CR <br />BELOW DOMINGUEZ CR <br />GAGE AT WHlTEWATER (BELOW EAST CR) <br />CONFLUENCE WITH COLORADO RIVER <br /> <br />a <br /> <br />a <br /> <br />b <br />b <br />b <br /> <br />7274 mi' <br /> <br />7532 mi' <br />7928 mi' <br /> <br />G5 <br />G6 <br />G7 <br /> <br />a <br /> <br />8010 mi" <br /> <br />b <br /> <br />So\ll'teS of Drainage Areas <br /> <br />a Determined from published information and USGS gage values <br />b Determined from upstream USGS gage information combined with planimetering <br />,., FEMA published value at confluence (7870 mi~ was found to be unverifiable based on the USGS gage value at a location approximately 9 <br />miles upstream <br /> <br />Only one problem was encountered during the drainage area determinations. The drainage area <br />published by FEMA for the mouth of the Gunnison River in the Delta County FIS (7870 mi2) <br />was found to be lower than the value at the USGS gage location approximately 9 miles upstream <br />at Whitewater. The value at the gage location (7928 mi2) was used as a base value and <br />planimetering downstream to the confluence provided the confluence value for this report (8010 <br />mi2). The FEMA value was assumed to be in error. <br /> <br />Figure 4 shows the study reach and each of the hydrologic analysis points listed in Table 2. <br /> <br />2.5 Flood Characteristics <br /> <br />Major flooding in the Gwmison 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 in late winter or early spring. Due to the small areal extent <br />and limited duration of thunderstollt1s, they do not typically constitute a major flood threat on <br />streams as large as the Gunnison or Uncompahgre Rivers. They do, however pose a problem for <br />some of the smaller tributaries in the Gunnison River basin. <br /> <br />Snowmelt flooding is characterized by moderate peak flows, large volume of runoff, long <br />duration, and diurnal fluctuation of flow. Flooding from general rainfall alone, though <br />uncommon on the Gunnison River, is characterized by high peak flows and moderate duration <br /> <br />6 <br />