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<br />agricultural, but today commercial, industrial, and residential
<br />development has encroached onto the floodplain. In various reaches
<br />of the floodplains, development pressures continue to exist. The
<br />county government is working to retain the open space of the
<br />floodplain areas.
<br />
<br />2.3 Principal Flood Problems
<br />
<br />.
<br />
<br />The South Platte River flows through the western edge of Arapahoe
<br />County in shifting channels in a broad, shallow bed with low, flat
<br />overbanks. Streams tributary to the South Platte River are
<br />ephemeral and flow in steep, narrow channels; whereas those in the
<br />eastern two-thirds of the county flow in wide, flat channels
<br />similar to the South Platte River.
<br />
<br />All streams studied have had various structural improvements but
<br />the intense and infrequent thunderstorms characteristic of the area
<br />can generate floods in excess of existing structural capacities.
<br />The flood threat throughout the county has not been adequately
<br />defined and urbanization has occurred in certain areas without
<br />regard to the hazard.
<br />
<br />Major floods have occurred on the South Platte River and its
<br />tributaries in Arapahoe County since 1844. During the period, 11
<br />devastating floods have occurred on the South Platte River; 17 have
<br />occurred on Cherry Creek; and 3 each have occurred on Box Elder,
<br />Comanche, and Bijou Creeks. Historic flood information on other
<br />streams in Arapahoe County is not available.
<br />
<br />In 1844 and 1864, reports read, "bottomlands near Denver were
<br />covered with water bluff to bluff." By 1876, encroachment into the
<br />floodplain had developed to such an extent that on May 23, 1876,
<br />the Rocky Mountain News reported, "(The South Platte River) was
<br />higher to be sure--several feet higher perhaps in l864--but it was
<br />not able to work such destruction at that time as now. There was
<br />not so much town here in 1864, as now, nor as many bridges."
<br />
<br />~
<br />
<br />The most significant floods of recent times on the South Platte
<br />River occurred in 1912, 1921, 1933, 1935, 1942, and 1965 during
<br />which discharges of 13,000 cubic feet per second (cfs), 8,790 cfs,
<br />22,000 cfs, 12,320 cfs, 10,200 cfs, and 40,300 cfs, respectively,
<br />were recorded. Cherry Creek experienced a similar flood history,
<br />with discharges of 25,000 cfs, 34,000 cfs, 10,700 cfs, 17,600 cfs,
<br />10,800 cfs and 39,900 cfs in 1912, 1933, 1945, 1946, 1963, and
<br />1956, respectively.
<br />
<br />.
<br />
<br />In interviews held in Watkins, Strasburg, Byers, and Deer Trail
<br />regarding flood histories on Box Elder Creek, Comanche Creek, West
<br />Bijou Creek, and East Bijou Creek, residents recalled severe damage
<br />and lost lives in floods occurring in 1905, 1935, and 1965.
<br />
<br />All of these floods of record on the
<br />tributaries have been generated near their
<br />of Monument Divide, a high ridge located
<br />
<br />South Platte River and
<br />headwaters on the slopes
<br />between Castle Rock and
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<br />7
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