|
<br />Records show that, since the turn of the century, notable high
<br />flows occurred on the Uncompahgre River in 1921, 1927, 1938, 1941,
<br />1944, 1947, 1957, 1973, and 1975. The largest known flood, esti-
<br />mated peak flow of 5,140 cfs as recorded at the Colona stream gage
<br />(approximately 20 miles upstream of Olathe), occurred approximately
<br />mid-June 1921 as a result of snowmelt. Based on the results of
<br />this study, the 1921 flood is estimated to have been slightly larger
<br />than the 100-year frequency flood. The only notable cloudburst
<br />flood of record occurred in July 1923. Peak flows of the larger
<br />historical floods on the Uncompahgre River are shown in Table 3.
<br />
<br />Historical flooding in the Uncompahgre Valley, described in avail-
<br />able news articles, has damaged or destroyed railroad track and
<br />embankments, road and railroad bridges, roads, diversion structures,
<br />and buildings and their contents. Inundation of agricultural prop-
<br />erty has eroded farmlands; damaged and destroyed crops and irriga-
<br />tion systems; reduced soil productivity as the result of increased
<br />salinity; and deposited sand, silt, and debris on cropland and
<br />pasture, Railroad and highway traffic has been disrupted, public
<br />utilities damaged and destroyed, homes evacuated for as long as
<br />several days, and cattle moved to higher ground to protect them
<br />from the possibility of drowning.
<br />
<br />According to newspaper articles from the Montrose Daily Press cited
<br />in a floodplain information and urban drainage report (Reference 4),
<br />notable floods occurred in the Montrose area in 1938, 1964, and
<br />1967. This area includes the Cedar Creek, Dry Cedar Creek, and
<br />Montrose Arroyo basins, However, no historical records of flooding
<br />are available for any separate stream, Also, no historical records
<br />of flooding are available for the Hieroglyphics Canyon and Happy
<br />Canyon Creek basins, Figures 2 through 10 show examples of flooding
<br />problems in Montrose County,
<br />
<br />2.4 Flood Protection Measures
<br />
<br />As of June 1980, no flood-control projects affecting floodflows or
<br />flood elevations were in existence. However, the Dallas Creek
<br />project, located at Ridgeway, Colorado, creates a reservoir that
<br />has 80,000 acre-feet of storage, with an additional flood-control
<br />storage for spring runoff of 26,000 acre-feet. A 1973 U.s. Army
<br />Corps of Engineers report states that this project will reduce the
<br />standard project flood of 7,000 cfs to a flow of 3,700 cfs at the
<br />dam site. Although this could provide incidental flood-control
<br />benefits to downstream flood plain areas, flood control is not a
<br />function of this project. Therefore, any effects of the Dallas
<br />Creek project were not included in this study (Reference 5).
<br />
<br />Improvements such as dikes and bank protection have been made at
<br />various locations along the Uncompahgre River. Some incidental
<br />flood protection is provided by several irrigation canals that
<br />branch off from the river at different locations upstream of the
<br />
<br />~
<br />
|