FLOOD05622

• County: Arapahoe
• Community: Aurora
• Stream Name: Sable Ditch
• Basin: South Platte
• Title: Sable Ditch Request for Letter of Map Revision
• Date: 8/1/1993
• Prepared For: Arapahoe County
• Prepared By: Aurora
• Floodplain - Doc Type: Miscellaneous

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2nd cross-section:
cul vert:.

section 8.0, at downstream end of

3rd cross-section:
cul vert:.

Section 9.0, at upstream end of

4th cross-section:

section 9.5, at toe of first drop.
Section 10.0, at top of first drop.
section 10.5, at toe of second drop.
section 11.0, at top of second drop.

5th cross-section:

6th cross-section:

7th cross-section:

8th cross-section: section 12.0, 150' upstream of second
drop.

sections 9.5, 10.0, 10.5, 11.0 and 12.0 are equivalent to
sections 9.5, 10.0, 10.5, 11.0 and 12.0 in the submittal
for the request of LOMR in March 1982. Also, section
12.0 is identified as cross-section "E" on the Flood
Insurance Rate Map.

statiohs and elevations for sections 7.0 through 10.0 are
from as-built survey.

stations and elevations for Sections 10.5 through 12.0
are from the March 1982 submittal (there have been no
changes to the concrete channel since then).

The approximate lOa-year water surface elevation at
section 7.0 (first cross-section) is 5362.0. This value
is taken from the Flood Insurance Rate Map.

4 .

Manning's "n" Coefficients

Manning's roughness values used are as follows:

n = 0.015 concrete channel

n = 0.013 concrete box culvert

n 0.040 over bank areas, good vegetation

5.

Computations

Copies of the HEC-2 input, output and summary tables are
included in Appendix B.

The proposed laO-year flood plain with the profile of the
lOa-year flood is shown on the drawings, included in the
back pocket of this report.

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