FLOOD07245

• County: Arapahoe
• Community: Greenwood Village
• Stream Name: Goldsmith Gulch
• Basin: South Platte
• Title: Request For Conditional Letter of Map Revision
• Date: 6/1/1991
• Prepared For: BBSC
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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INTRODUCTION

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The purpose of this report and supporting documentation ia to request

revisions to the 1989 published Flood Insurance Study (FIS) for a portion of

Goldsmith Gulch between East Belleview Avenue and Yosemite Street in Greenwood

Village, Colorado. Note that the 1989 study is a County wide study for

Arapahoe County, which includes Greenwood Village.

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The project proposes to relocate the channel thalweg and provide channel

improvements for flood and erosion control. The entire reach is on private

property owned by the requestees. Public Notice was not issued since the

requestec is the only affected property owner. The study area is shown on

the attached copy of the Flood Insurance Rate Map (FIRM). See Figure 1 in

the Appendix.

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Supporting documentation includes hydraulic computations for the proposed

conditions, existing conditions, duplication of the Flood Insurance Study,

and mapping for existing and proposed conditions.

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II. BACKGROUND

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The 1989 FIRM shows detailed flood mapping for Goldsmith Gulch through the

study reach under consideration (Figure 1). The information used for the

FEMA Study was based on a hydraulic analysis completed for the Urban Drainage

and Flood Control District's 'Flood Hazard Area Delineation" (FHAD) Study for

Goldsmith Gulch in 1976. To demonstrate that our HEC-2 model is working

properly, a duplication of the hydraulics was completed. The only backup

data available was obtained from the Colorado Vater Conservation Board and

the Urban Drainage and Flood Control District. This information included

the 100-year run from the 1976 FHAD Study. A duplication of this data

presents a "calibration run' which matches the FEHA Floodway Table for the

lOO-year water surface elevations (see Figure 2 in the Appendix).

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