FLOOD06593

• County: Larimer
• Community: Loveland
• Stream Name: Big Thompson River
• Basin: South Platte
• Title: Floodplain Information Report
• Date: 12/1/1971
• Prepared For: Loveland
• Prepared By: US Army Corps of Engineers
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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in the study reach, are above the Intermediate qesional Flood (I ,R,F.l.
Portions of the approach roadways are overtoopec except at road I I~
where al I of the I.R.F, flows would be confined in the channel under
the bridge.

PAST FLOODS

This section describes the flood histories and storm
characteristics typical of the Loveland area.

Obstructions to Flood Flows

Elevated roadways that cross the flood olain imoede flood

flows and raise the water surface to a degree dependent on the hei~ht

of the roadway and the size of the waterway opening at the bridge,

likewise irrigation diversion structures may impede flood flows.

The diversion dams or weirs impede channel flows whi Ie the embank-

ments adjacent to the diversion ditches impede overbank flows. The

effects of the roadway and irrigation diversion obstructions are

shown in table 2, Flood Plain Reference Data, and on the Profi Ie

Plates 3, 4 and 5 at the end of this report. Aoproximate elevations

of the bridse deck and top of waterway~1 are also shown on the oro-

files,

Flood RecordJ.!
A stream gage was operated in the vicinity of the
Loveland and Greeley Oanal diversion at the western side of Loveland
trom June 1947 to September 1955. Flood events during the period
of operation occurred 4 June 1949 and 3 August 1951 with respective
discharges of 7,750 c.f.s. and 22,000 c,f.s. Stream gaging stations
located in the reach 4 to 6 mi les east of Drake near the mouth of
the canyon have been operated intermittently since 1887. These
records indicated that floods occurred about once every 6 years on
the average. The drainage area upstream of the Drake gage (mouth
of the canyon) is only 60 percent of the drainage area upstream of
loveland, Flooding at Loveland may not have always corresponded
to flooding at the Drake gage. Various sources indicate that floods
occurred in the Loveland vicinity in 1864, 1894, 1906, 1919, 1921,
1923, 1938, 1941, 1942, 1945, 1949 and 1951,

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Duration and Rate of Rise

Past records of floods in the Loveland area show that

overbank f lows can last from "a few hours" to more than 12 hours.

Potential large floods at Loveland could last from one to two days.

A cloudburst in the lower basin could result in flooding at Loveland

in two or three hours, A storm in the upper basin would produce

high waters at Loveland in from 10 to 20 hours.

II See Glossary of Terms,

II Flood descriptions before 1923 ',lOre taken from "Floods in
Co I orado," 'A'a ter Sup ply Pa per 997, LJ. S, Depa rtment of I nte r i or.
Other data were obtained fram U. S. Department of Commerce,
Climatological Data Publications, various U. S. Geological Survey
Water Supply records, and Oorps of Engineers' flood records.

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