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

4-7 June 1949
Heavy ra ins. i n the headwaters area of the B.ig Thompson
basin resulted in a peak discharge on 4 June of 3,330 c.f.s. at
the Drake station and 7,750 c.f.s. at the Loveland station. Rainfal I
amounts on 4 June were 2.75 Inches at Estes Park and 3.66 inches
at Waterdale. Between 4 and 7 June, Estes Park received 3.92 Inches
of rainfal I whi Ie Waterdale received 5.30 inches. Lowland areas
west of Loveland were flooded and U. S. Highway 34 to Estes Park
was damaged.

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3-4 August 1951
On 2 and 3 August 1951, intense rains over much of the
basin caused severe flooding along the Big Thompson River from
Buckhorn Creek to the mouth. The peak discharge at Drake was 3,530
c.f.s. on 3 August. At the river mouth the flow peaked at 6,100
c.f.s. on 4 August. Estes Park received 1.31 inches of rain during
2 and 3 August; Waterdale measured 4.64 Inches, of which 4.18
inches fel.1 on 2 August. On Buckhorn Creek a dam containing about
1,000 acre-feet of stored water, fai led at 10:00 p.m. on 3 August.
The flood crest reached Loveland at 11:30 p.m. and the peak there
was estimated to be 22,000 c.f.s. The river was reported to be
a ml Ie wide in places. Numerous rural homes were flooded, many
swept from their foundations. One mile of U. S. Highway 34 west
of Loveland was washed away. Irrigation works such as diversion
dams and canals were destroyed, crop loss was heavy, and there was
much sediment and erosion damage. The lives of four people were
lost and many were left homeless. Total damages from the flood
were estimated at $602,000.

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POTENTIAL FLOODS

This section discusses the Intermediate Regional and
Standard Project Floods and their effects. The Intermediate Regional
Flood represents a flood with an average frequency of occurrence of
about once in 100 years and is increasingly being accepted by the
pub Ii c as a mi n imum IImi t for app lleat ion of I oca I regu lat r ons,
The Standard Project Flood is of greater magnitude and represents a
reasonable upper limit of expected flooding. However, it is not the
largest flood that could occur. It is emphasized here that floods,
which are sma I ler than the Intermediate Regional Flood would be more
frequent. Although these lesser floods would inundate sma I ler areas
they would also cause damage, hardship, and inconveniences.

Intermediate Regional Flood

The natural flow of the Big Thompson River is affected

by transmountaln diversion from the western slope of the Rocky Moun-

ta r ns, storage. reservo Irs, power deve I opments, divers ions for i rr 1-

gation, and return flow from irrigated areas, al I of which were con-

sidered in determining potential floods. A statistical analysis

was made of 38 years of stream gaging records at the Drake station

to deve lop a dl scharge probab i I i ty curve. Th is curve was then

adjusted so as to apply to Loveland. The Intermediate Regional

Flood d i scha rge at Love I a nd I s I 9,000 c.f. s.

Standard Project Flood

The Standard Project Flood ,is presented in this report

as the pract ica I upper I 1m it of flood i ng. Storms that \;ou I d produce

this flood are uncommon, and It Is difficult to assign frequencies

of occurrence with any reasonable degree of accuracy. The magnitude

of such a storm is typified by those in the Denver area in 1965

that resulted in catastrophic floods on several South Platte River

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