FLOOD11626

• Floodplain - Doc Type: Floodplain Report/Masterplan

Gold Star Canyon
Floodplain Information Report

Mesa County, Colorado

meter pixel resolution color digital orthophotography

Deliverables
ESRI Shape Files of topographic basemap

1

Imagery
. NAIP

culvert which is 1/3 full of silt. Maintenance reports show the structure as 7 feet tall, usually with 2 to 3
feet of siltlmud/debris in the bottom. The model assumed l' -4" silt in the bottom, and 5' -8" available
opening. In general, the flood elevations shown on the profiles are thus considered valid only if
hydraulic structures remain unobstructed, operate properly, and do not fail. No bulking factor has been
multiplied to the hydrology results, even though it is clear silt and mud are mobilized during significant
runoff events.

Central Zone, North

88)

(SPCS),

(NA VD

Datums I Units
Horizontal Datum - Colorado State Plane Coordinate System
American Datum of 1983 (NAD '83)
Vertical Datum - North American Vertical
Units - UTM meters converted to U.S. feet

1988

Datum of

Pro1 ect

The hydraulic analysis of the study area was based on subcritical depth computations and information
obtained from available GIS topographic data and field reconnaissance. The model was prepared
assuming that the flow is steady, gradually-varied, and can be modeled in one-dimension. The results of
the HEC-RAS hydraulic computer model can be seen in Table 2 - Flood Frequency - Elevation and
Discharge Data.

1944 South Broadway,"

Bibliography and References

LANDesign, LLC, "Floodplain Delineation Report for the Gigoux Property,
revised January 7, 2004.

1

7.0

Applications

The National Flood Insurance Program (NFIP), encourages State and local governments to adopt sound
Floodplain Management Programs. Therefore, each Flood Insurance Study provides 100-year flood
elevations and delineation of the 100-year floodplain boundary to assist communities in developing
floodplain management measures

Floodplain Management

4.1

Floodplain Boundaries

5.0

1997

Natural Resources Conservation Service, letter to Kent Wagoner in regards to Gigoux Property
Floodplain Delineation Report by LANDesign, LLC, November 24, 2003

19,

LANDesign, LLC, "Drainage Report for the Preserve Subdivision, June

Mesa County GIS Data, including contours, 2001

Mesa County Aerial Photographs, 2001

2

4

5

3

To provide a national standard without regional discrimination, the 1 percent annual chance (lOO-year)
flood has been adopted by FEMA as the base flood for floodplain management purposes. For Gold Star
Canyon, the 100-year floodplain boundary has been delineated using the flood elevations determined at
each cross section. The floodplain boundaries were interpolated between the modeled cross sections
using the topographic contours with an interval of 2 feet that were obtained from the GIS mapping data
provided by Mesa County

Release 55

Technical

Watersheds,

for Small

U.S. Department of Agriculture, Urban H
June 1986.

6

The 100-year floodplain boundary is shown on the attached Floodplain Maps (Sheets 1 through 5). On
these maps, the 100-year floodplain boundary corresponds to the boundary of the areas of special flood
hazards (Zones AE).

Computer

U.S. Department of the Army, Corps of Engineers, Hydrologic Engineering Center,
Program HEC-HMS 3.0.0, Davis, California, January 2001.

7

Topography

6.0

itation-

Oceanic and Atmospheric Administration, Preci
Volume III-Colorado, 1973

Department of Commerce, National
Atlas of the Western United States

U.S
Fre

8

Mapping for Gold Star Canyon was obtained from Mesa County GIS Department from a county-wide
study completed in 2001 The following outlines the mapping specifications

Monument.

USGS_ 711z' Quadrangle, Colorado National

9

4

(DTM)

contour mapping

terrain model

)

Mapping
Photogrammetrically compiled digital
No planimetric feature collection
DTM accurate to support two-foot (2
Interpolate 2' contours from DTM