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<br />Dolores Water Conservancy District, McPhee Reservoir does not provide flood control storage
<br />for the Dolores River,
<br />
<br />The San Miguel River also originates on the west slope of the San Juan Mountains, with its
<br />headwaters immediately east of Telluride, The river flows west, then northwest, through the
<br />county, The San Miguel River is tributary to the Dolores River in Montrose County,
<br />approximately 16 miles north of San Miguel County. Elevations of the watersheds range from
<br />approximately over 14,200 feet to approximately 6500 feet as the Uncompahgre leaves the
<br />county, The watershed primarily consists of forested lands, with high elevation forests consisting
<br />of aspen, lodgepole pine, spruce, grass meadows and steep rock face and lower elevation forests
<br />consisting of spruce, ponderosa pine, cedar and scruboak, There are some agricultural lands in
<br />lower elevations, with grass hay and pastures the primary crops,
<br />
<br />There are several current USGS gaging stations within San Miguel County located along the
<br />major rivers and tributary streams, In addition, there are several sites that have collected data but
<br />are no longer active, However, most of these gaging stations do not contain enough data to
<br />calculate peak discharges, The gages for which adequate data available for peak discharge
<br />calculations are shown in the following section of the report, There are also several gaging
<br />stations upstream and downstream of San Miguel County along the Dolores River.
<br />
<br />Floodinl! Problems and Floodinl! History
<br />Floods in the subject watersheds normally occur during the months of late summer and early
<br />autumn and are caused primarily by intense localized cloudbursts or thunderstorms, Typically,
<br />these floods have high peak discharges with low volumes over short durations and there is
<br />usually a very short window of opportunity for flood warning and evacuation once a major
<br />storms hits the area, Less damaging floods can also result from rapid melting of mountain
<br />snowpack in the spring and early summer months, especially on the larger drainageways. A
<br />combination of rainfall and snowmelt can sometimes prove to be the worst flooding scenario for
<br />Colorado's mountain streams,
<br />
<br />The PIS does not discuss flooding in the Dolores River sub-basin, However, examination of the
<br />USGS gage records for the Dolores River at Bedrock gage indicate that flooding occurred in
<br />1973,1975, 1979, 1980 and 1983,
<br />
<br />The PIS reported severe flooding along the San Miguel river in 1909 and 1911, with lesser floods
<br />occurring in 1913, 1923, 1927, 1964 and 1966. Peak discharges at the Placerville gage were
<br />estimated at 10,000 cfs for the 1909 event and measured at 2,380 for the 1911 event. Using the
<br />PIS hydrology, this corresponds to a greater than SOD-year and less than a lO-year event
<br />respectively, The most recent event occurred in 1983, when the Placerville gage peaked at 3,830
<br />cfs, Flooding caused failures of small dams and the loss of one life,
<br />
<br />The PIS reports that flood damage in Telluride is primarily caused debris and mud flows from
<br />Cornet Creek. The two most destructive events occurred in 1914 and 1969, and were due to
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