FLOOD07213

• Designation Number: 85
• County: Adams
• County: Arapahoe
• County: Douglas
• Community: Denver Metro Region
• Stream Name: Weir Gulch Tributaries
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Weir Gulch Tributaries, 1st Avenue and Dakota Avenue - Lakewood and Denver, CO
• Date: 7/1/1977
• Designation Date: 11/1/1977
• Floodplain - Doc Type: Floodplain Report/Masterplan

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3

FLOOD HISTORY

"2. The most upstream report of high water cal'1e from a resident at
6200 Nevada Place. This person said water had flowed as high
as the sidewalk on both sides of the street.

4. Immediately upstream of So. Eaton St. the flood channel is ter-
minated and a 42-inch diameter pipe is orovided for conveyance
(see sheet 7). The inlet of this pipe was free of debris, but
the City of Lakewood was in the area that morning and could have
cleaned the inlet. Evidence of hioh water on fences across Sa.
Eaton St. was as high as 1.5 feet." The lady livinq north of the
drainageway an So. Eaton St. showed where her vegetable garden
nad washed away. She experienced no other property damage.

7. Deposits of sediment and debris showed where water left the banks of
the channel between secti ons 26 + 00 and 20 + 40 on sheet 8."

Flood history on record for the two tributaries is limited to occasional

complaints filed by telephone with the City of Denver. Centennial Engineerir;,

Inc., staff conducted interviews with residents in areas where calculations

indicated a potential flooding problem exists.

Along the 1st Avenue Tributary, no specific problems were reported for the a'~a

west of Sheridan Boulevard. The lower lying areas east of Sheridan Boulevarc
seem to be subject to flooding on a more frequent than annual basis. Resi-
dents reported having water in their yards and basements during or after any
heavy rainstorm and complained about "sewage-like odors" coming from the oper
channel portion located close to the mouth of the tributary. The lack of
maintenance on these channels is the apparent reason for the growth in the
channel to generate enough resistance to cause overtopping even at low-intensity

Flood experience seems less frequent and not as severe as on 1st Avenue Tributary.

HYDROLOGY

The two tributaries were each divided into subbasins. The Colorado Urban

Hydrograph Procedure was used to develop peak discharges at the design point

of each subbasin for the 5, 10, 50, and 100-year recurrence intervals for

storms.

future dAvelopment conditions.

Along the Dakota Avenue Tributary, flooded basements were not reported. Residents
on Eaton Street observed that "once in awhile" flow overtops the roadway.
Ponding was observed east of Depew Street, but no specific dates could be
remembered. At Sheridan Boulevard and east of Sheridan Boulevard, it was

Rainfall Data

The rainfall intensity was assumed to be the same over the entire drainage

basin for a three-hour duration. The values listed below for rainfall depth

are taken from project "REUSE" for Jefferson County, T4S" R69W, and were used

for both drainage basins.

observed that water flowing down Alaska Place would run across Yates Street

through the yards down to Xavier Street. A recent storm (June 6, 1977) provided

evidence of flood problems in the area. Residents reported 30 to 60 minutes

of heavy rain, and an inspection was made on the afternoon of June 7, 1977.

Following are excerpts from the inspection memorandum2 which illustrates

typical flood problems.

TABLE 1
RAINFALL DATA

Depth (Inches)

Frequency 1 hour 6 hours
2- Year .68 1.12
10-Year 1.50 2.50
50-Year 1.83 3.16
100-Year 2.00 3.50

Losses

Based on the recommendations given in the "Urban Storm Drainage Criteria

~1anual", the following criteria for losses were applied to calculate the run-

2File memorandum by Jon Sorenson, L. Rice Consulting Water Engineers, dated
June 8,1977, Job No. 41.01.