FLOOD10617 ‎(2)‎

• County: Boulder
• Community: Boulder County and Incorporated Areas
• Title: FIS - Boulder County and Incorporated Areas - Vol 1
• Date: 10/4/2002
• Prepared For: Boulder County
• Prepared By: FEMA
• Floodplain - Doc Type: Current FEMA Regulatory Floodplain Information

tenth of an inch per event) than the areas adjacent to the
foothills. The occurrence of precipitation varies; however, most
of the rainfall is concentrated in May. Thundersto~s also occur
irregularly throughout the summer months. The temperature extremes
at Boulder are evidenced by mean maximums ranging fram 46.3 degrees
Fahrenheit (OF) in January to 88.30F in July, and by mean minimums
ranging from 21.60F in January to 61.00P in JUly.

The City of Boulder is located in central Boulder County, along the
foothills of the Front Range. In 1980, Boulder had a population of
76,685 (Reference 13), an increase of 14.7 percent since 1970.
This population growth is expected to continue with further
expansion into identified floodplain areas.

The study area includes the drainage basins of seven streams
located throughout the Boulder area. All study streams are
tributary to Boulder creek, with a total drainage area of
approximately 23.2 square miles. The elevation of Boulder ranges
from 8,520 feet at the headwaters of Pourmile Canyon Creek to
5,155 feet at the confluence of Pourmile Canyon Creek with Boulder
Creek.

All stream reaches east of the foothills, except for those on
Fourmile Canyon Creek, are located within urbanized areas with
occasional open-space and park areas. The terrain of these
subbasins consists of mild slopes with topsoils in the B and C
hydrologic soils group with same D soils. Vegetation for most of
the stream reaches is characteristic of urban areas. Fourmile
CanyoD Creek is located in sparsely developed agricultural areas.
Vegetation along Fourmdle Canyon Creek and the downstream reaches
of Bear, Skunk, Goose, and Wonderland Creeks consists of natural
grasses and weeds.

The Town of Jamestown is a small mountain community located in the
central northwest section of Boulder County, approximately 10 miles
northwest of the City of Boulder. The 1970 population was 185, and
was estimated at 240 in 1980. Communities near Jamestown are
Lyons, approximately 11 miles to the northeast, and Longment,
approximately 16 miles to the east.

Historically a mining tOWD, Jamestown is now a residential
community. Most of its residents are commuters to either Boulder,
Denver, or LODgment.

Little James creek, draining an area of
miles, joins James Creek at Jamestown.
drainage area of 14.5 square miles at the
is a tributary to Lefthand Creek, which
St. Vrain Creek Dear Longmont. Rainfall
nearly 24 inches annually.

approximately 3 square
James Creek, with a
downstream study limit,
flows eastward to join
in the basin averages

The terrain is mountainous with steep slopes. The soils of the
Allen Park Series, which formed on the mountain slopes between
elevatioDS of 6,300 and 8,200 feet, are loamy colluvium and
weathered granite residuum. The surface layer, approximately

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