FLOOD10171

• Designation Number: 218
• County: Boulder
• Community: Unincorporated Boulder County
• Stream Name: Lower Boulder Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Lower Boulder Creek - Valley View Road to Boulder Weld County Line
• Date: 3/1/1983
• Designation Date: 7/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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FLOOD HISTORY -

swollen into a great river, in many places fully a mile and a half wide,
inundated the land and farms and meadows and swept away fences and bridges,"

Information on past floods was obtained from the Corps of Engineers and the
U.S. Geological Survey (USGS) publication entitled Floods in Colorado (Reference
7). Stream gaging records maintained by the U.S. Geological Survey on Boulder
Creek are described in Table 1,

FLOOD of 29 May - 2 June, 1894

Heavy rains fell over the mountains extending from the Colorado-Wyoming border
southward into the Republican and Arkansas River basins. Rainfall over the
Boulder and South Boulder Creek basins was particularly heavy. Rainfall records
for a 96-hour period ending at 3 a.m. on 2 June 1894 indicate that the mountain
drainage area received from 4.5 to 6.0 inches of precipitation. Rainfall
amounts over the high plains gradually decreased from west to east and varied
from 5 inches at Boulder to approximately 2.5 inches at the mouth. The
mountain rainfall combined with the snowmelt runoff produced the greatest
flood known at Boulder inundating the valley during the night of 30 May 1894.
Buildings, bridges, roads and railroads were washed away. Computations made
18 years later produced estimates of the peak discharge in Boulder that ranged
from 9,000 cubic feet per second to 13,600 cubic feet per second,

TABLE 1
STREAM GAGE RECORDS FOR BOULDER CREEK

Location

Approximate
Drainage Area
(sq.mi.)

102

Aug-Oct, 1887;
Apr-Oct, 1888;
1906-1914;
1916-present.

Gaging Records

Orodell

Boulder

129

1889-1892;
1895-1901;
1905-1908.

In Boulder, floodwaters covered the entire area between Water Street (Canyon Blvd.)
and University Hill to depths as great as eight feet. Every bridge in Boulder
and a number of residences were swept away. Other types of damage included
commercial establishments, public utilities, railroad property, roads and
streets, and irrigation structures. Many people were trapped in their homes
and had to be rescued. Only one life was lost; this was due, in part, to
the flood's slow onset.

Longmont

439

Mar 1927 to Sep 1949;
May 1951 to Sep 1955;
Oct 1978 to present.

Floods in the Boulder Creek basin are produced by intense rainfall during either
isolated or general storm systems. In addition, there is normally an increase
in flows during the mountain snowmelt period which is frequently augmented by
rainfall runoff. Flooding has occurred along Boulder Creek in 1864, 1876,
1894, 1914, 1923, 1938, and 1969. Descriptions of major floods that may have
affected the study reach are presented below.

In the valley downstream from Boulder, the floodplain was reported to have
been inundated to an average width of approximately one mile for several days.
Agricultural damages included loss of livestock, crops, pastures, fences,
roads and deposition of sand and silt on floodplain lands. In addition,
considerable crop losses were suffered on lands outside the floodplain which
were dependent on irrigation diversions from Boulder Creek.

FLOOD of 21-23 May, 1876

Little is known about the 1876 flood. A general storm over the Boulder Creek
basin created flooding on the plains of reportedly It miles wide. Railroad
service to Boulder was disrupted. The Greeley Tribune reported "The Boulder,

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