FLOOD05064

• Designation Number: 205
• County: Larimer
• Community: Fort Collins
• Basin: South Platte
• Title: Master Drainageway Planning - Cooper Slough, Boxelder Creek, Fort Collins, Larimer County, Colorado
• Date: 8/1/1981
• Designation Date: 1/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Soils
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"The Boxelder, a small stream ordinarily only a few feet wide,
was tearing down through a fertile valley filled from bluff to
bluff with a sheet of water a mile wide, carrying buildings and
bridges away..."

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Soils in the watershed are quite variable but may be divided into four

areas. The first area would include the shallow to rnodarately deep soils

developed on the granites of the northwest portion of the watershed. The

western portion is characterized by a series of steep ridges, cliffs and

narrow valleys in sandstone, shale and limestone bedrock. East facing soils

are shallow with many rock exposures, west facing slopes are of very steep

rocky, colluvial soils with deep alluvial soils in the valleys. Moderately

deep gravelly soils on small plateau or mesa like areas make up most of the

area in the northeast. Soils of the irrigated land are dominantly deep or

moderately deep loarns over shales, sandstone or gravels. The larger drainages

are dominantly alluvial soils of loam to clay loam in texture.

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Information obtained in August 1969 from land owners in the floodplain

for the years 1959 through 1969 indicate that flood damage occurs somewhere in

the watershed each year. Estimated damage from these storms follows:

August 1, 1961; one 50- to 100-year frequency storm in the vicinity of

Wellington, Colorado. Forty basements were flooded in addition to agri-

cultural and non-agricultural crops and property, with damages at $76,150.

June 1963; one 25- to 50-year frequency storm over a ve~y small area.

Estimated damages, $7200.

June 14 through 17, 1965, one 2-year, two l-year, and one 25-year fre-

quency storms with some overlapping of areas. Estimated 'damages, $96,000.

May 30 and June 4, 1967; two 25-year frequency storms overlapping over a

relatively small area in the vicinity of Wellington, Colorado. Estimated

damages of $46,100 with four lives lost at a county road bridge washout.

August 4, 1969; a l-year frequency storm occurring over a small area.

Damage estimated at $4000.

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Water Quality

The effect of urbanization on the quality of storm water runoff is to

transfer more pollutants (typical of urban areas), to other areas in the basin

and into larger bodies of water such as streams and lakes. The transfer of

urban pollutants, such as sediment, trash, salts, fertilizers and similar

ground deposits, may be detrimental to stream and lake waters and to areas

which are subject to flooding by storm waters. Urbanization with decreased

areas of vegetation and permeable surfaces will contribute larger amounts of

pollutants due to the increased storm water flow rates and volumes.

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Flood History
Boxelder Creek has a long history of flooding. Floods of record occurred
in 1969, 1967, 1965, 1963, 1961, 1947, 1937, 1933, 1930, 1922, 1909, and 1904.
There is no official gauging station in the watershed and no known flood flows
have been measured. In general, information on past floods is based on
newspaper accounts and interviews with residents of the area.
The earliest known flood was in 1904. The flood of May 20 and 21, 1904,
resulted from rains of "cloudburst intensity" in the foothills at about 7000
feet elevation on the headwaters of the North Fork Cache la poudre River and
Boxelder Creek. Damage was heavy at Fort Collins and Boxelder Creek,
downstream of Fort Collins, COlorado, contributed high flows. The Greeley
Tribune stated:

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