FLOOD10335 ‎(2)‎

• Designation Number: 589
• County: Adams
• Community: Adams County
• Stream Name: Clear Creek
• Title: FHAD - Clear Creek ‎(Adams County)‎
• Date: 12/1/2005
• Prepared For: Adams County, CDOT, UDFCD
• Prepared By: Ayres Associates
• Floodplain - Doc Type: Floodplain Report/Masterplan

I

I

The information in this report does not imply any state action to zone or regulate use of floodplains. The
District has the authority to regulate floodplains, but to date has chosen to leave floodplain regulation
responsibility with local governments. The report provides a suitable basis for the adoption of land use
controls to guide floodplain management, with consideration for environmental attributes, and thereby
prevent intensification of flood losses.

1

The entire basin boundary is shown on

the Basin Boundary Map

(Figure

1 )

IWRES
ASSOCiJ\7'ES

I

I

I

I

Flood Hazard Area Delineation Maps are included in this report and they indicate the approximate
floodplain areas inundated by the 1 OO-year flood event. Flood profiles are also included and show the
water depths relative to the streambed and flood elevations for the 1 OO-year and 1 O-year flood events.
Water surface elevations are provided at each channel cross section in Table 1 and Table 2. These
elevations indicate a constant water depth across the full width of the stream valley. Valley cross sections
are plotted on the profile sheets at specified locations with predicted water depths during the 1 OO-year and
1 O-year events shown on the drawing. The flood profiles and flooded area data presented are based on
future, developed conditions in the Clear Creek basin. Possible future improvements to control floods are
not a consideration of this report.

The Clear Creek floodplain through Adams County is largely comprised of a mix of developed and
undeveloped land and gravel mining operations. Residential areas in the vicinity of 52nd Avenue and
Sheridan Boulevard in Adams County would be inundated by a 1 OO-year frequency flood.

Clear Creek, a left bank tributary to the South Platte River, has its source in the Rocky Mountains west of
Denver. Flowing in a generally easterly direction from the Continental Divide, Clear Creek enters the high
plains at Golden. The drainage area at the Golden gage near the bluff line is 400 square miles. From
Golden, Clear Creek flows in a northeasterly direction to its confluence with the South Platte River near
Derby. The Derby gage, which is located 0.6 miles upstream from the mouth of Clear Creek, has a
drainage area of 575 square miles. Elevations in the basin range from 5,100 feet above mean sea level to
over 14,000 feet above mean sea level (Landmark 1995-1998).

I

This report was prepared for the guidance of local officials in planning the use and regulation of the 100-
year floodplain. The report includes information on past floods and the nature and extent of probable future
floods along the study reach. The 1 OO-year flood should be given appropriate consideration before
planning for development in flood prone areas

The study area includes the reach of Clear Creek from its confluence with the South Platte River to
Sheridan Boulevard. Within this reach, Clear Creek passes through unincorporated areas of Adams
County.

I

I

Purpose and Scope

It should be noted that the terms "Intermediate Regional Flood," "1 OO-year flood
can be used interchangeably as they all define the same magnitude flood event.

and "one percent flood

STUDY AREA DESCRIPTION

The cooperation of local officials and public and private interests in providing assistance and information
was most helpful. We would also like to acknowledge the assistance received from the District, Adams
County, and the CDOT.

I

I

"

Upon acceptance of this report by the District and the designation and approval of this report by the
Colorado Water Conservation Board (CWCB), the areas described as being inundated by the 100-year
flood (Intermediate Regional Flood) may be designated as flood hazard areas and their use regulated
accordingly.

Acknowledgements

as stated in Section 30-28-201 for county governments and Section 31-23-201 for
of the Colorado Revised Statutes 1973

Vertical control is in U.S. feet, based on National Geodetic Reference System first order marks, North
American Vertical Datum (NA VD) 1988 datum. Elevation of the project grid is 5,000 feet-mean sea level
(msl). The mapping was prepared at a contour interval of 2 feet at a scale of 1:1,200 and conforms to
National Map Accuracy Standards (NAMAS).

I

I

municipal governments

"...to establish, regulate, restrict and limit such uses on or along any storm or
floodwater runoff channel or basin, as such storm or floodwater runoff basin has
been designated and approved by the Colorado Water Conservation Board, in order
to lessen or avoid the hazards to persons and damage to property resulting from the
accumulation of storm or floodwaters...."

.

.

The Combined Project

Easting State Plane Value/Combined Project

Factor equals 0.999791999

Factor - 3.000.000

I

I

I

This report was authorized by the Urban Drainage and Flood Control District (District) and under joint
sponsorship with Adams County and the Colorado Department of Transportation (CDOT) under the August
18, 2004, agreement regarding "Flood Hazard Area Delineation Clear Creek (Adams County)," Agreement
No. 04-03.05. The District joins with local communities to make floodplain information and mapping
available for local governments to adopt and administer their own floodplain regulations with the assistance
of the District. The cities, incorporated towns, and counties within the study area may adopt these zoning
regulations.. .

.

Mapping for this project is based on aerial photography obtained by Adams County, the District, and Metro
Wastewater Reclamation District (MWRD) in 1995 and updated in 1998. Base map horizontal control is
based on the Colorado High Accuracy Reference Network (HARN), NAD 83-92 Modified State Plane U.S
feet, Colorado Central Zone (50). Modified coordinate system is:

Mapping

Northing State Plane Value/Combined Project

Factor -1

000.000

I

Authorization

Floodwater surface elevations and floodplain boundaries are often revised by road and bridge construction
floodplain development, flood control improvements or natural processes. Prior to using this report for
planning or design purposes, the user is advised to contact the District to determine if the information in
this report has been amended

I

I

PREFACE