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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Di~c.hR.r2P- ~l1hir'. fp-p-t per second lcfs)
10-YR 50-YR 100-YR 500-YR
Downstream of Belleview 605 1251 2200 2337
(Per Denver LOMR)
Upstream of Belleview 1270 1950 2250 3050
(FIRM Section A)
Yosemite Street 960 1500 1750 2390
(FIRM Section F)

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It should be noted that the flows used in the Denver LaMa are less than the

FEHA flows published in the 1989 FIS. The flows used in the Denver LOMR

considered detention behind road embankments in the upper basin, while the

FEHA flows do not. Based on discussions with Greenwood Village, agreements

have not been completed to secure the areas in the upper basin for detention.

Therefore, our analysis uses the current 1989 FEMA flows for the study reach

analys is.

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VI. HYDRAULICS FOR IMPROVEMENTS

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All hydraulics were completed using the U.S. Army Corp of Engineers HEC-2

step-backwater program. Manning' n' values for existing conditions range

between .04 to .045 for the channel and .045 to .055 for the banks. For

proposed improvements, additional 'n' values were used to reflect new

materials and include .015 for concrete, .03 for grass, .04 for cobbles, and

.045 for riprap.

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Starting water surface elevations at Station 258+32 are all at critical

depth and match the Denver LOMR as noted below:

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