FLOOD01547

• Designation Number: 201
• County: Boulder
• Community: Lyons
• Title: Flood Insurance Study - Lyons, Boulder County, Colorado
• Date: 2/1/1980
• Designation Date: 8/1/1982
• Floodplain - Doc Type: Floodplain Report/Masterplan

2.0 AREA STUDIED

2.1 Scope of Study

This Flood Insurance Study covers the incorporated area of the Town
of Lyons, Boulder County, Colorado. The area of study is shown on
the Vicinity Map (Figure 1).

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Floods caused by overflow of St. Vrain Creek, North St. Vrain Creek,
and South St. Vrain Creek were studied in detail.

Those areas studied by detailed methods were chosen with consideration
given to all proposed construction and forecasted development through
1982.

2.2

Community Description

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Lyons is located in north-central Boulder County, in north-central
Colorado, approxilnately 40 miles north of Denver. In 1970, the
population of Lyons was 958 (Reference 1) and is now estimated at
approxilnately 1300. Nearby communities include Longmont, 11 miles
southeast; Boulder, 16 miles south; and Estes Park, 20 miles northwest.
Lyons is bordered on all sides by unincorporated land of Boulder
County.

North St. Vrain Creek and South St. Vrain Creek drainage basins are
on the east slopes of the Rocky Mountains and join at Lyons, becoming
St. Vrain Creek. From there, St. Vrain Creek flows east to the South
Platte River.

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Rainfall in the mountains west of Lyons averages approximately 17
inches annually. The average'annual temperature in the basin is
approximately 40.F. The basin topography changes from forested
mountain terrain on the west, to rolling plains on the east, which
are prilnarily pasture and cultivated fields. The drainage area at
Lyons is 219 square miles, with 125 square miles on North St. Vrain
Creek and 94 square miles on South St. Vrain Creek.

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North St. Vrain Creek enters the town on vacant land near the north-
western corner of the community. In the areas south and west of
U.S. Highway 36, the existing zoning and land use is primarily
residential, consisting of mobile and single-family permanent homes.
West of Fifth Avenue the land is vacant. Between Fifth Avenue and
Second Avenue, the creek flows through a single-family residential
area, north of the business community.

South St. Vrain Creek parallels Colorado Highway 7, enters the
town near Fifth Avenue, and flows through residential land that is
partially developed with single-family residences and mobile homes.

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