FLOOD10157

• Designation Number: 74
• County: Arapahoe
• Community: Aurora
• Stream Name: Granby and Sable Ditches
• Basin: South Platte
• Title: FHAD - Granby and Sable Ditches, Aurora, Colorado
• Date: 4/1/1977
• Designation Date: 7/27/1977
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Table I
Drainage Areas

FLOOD HISTORY

Granby Ditch

Toll Gate Creek
Colfax Avenue
Laredo Street

Sable Ditch

Toll Gate Creek
Colfax Avenue

2.28
1.96
1.38

Little information is available on past flooding along Granby
and Sable Ditches. Discharge measurements, high water marks
and other flood data have not been officially recorded. Most
published accounts of past flooding in the area are related
to Toll Gate Creek, Sand Creek and the South Platte River.
When there was flooding on these other streams, however,
verbal au~ounts indicate that Granby and Sable Ditches were
also carrying unusually high flood flows. The only written
account of flooding on Granby Ditch was reported in the Aurora
Advocate Sentinel on May 9, 1973. This flooding was caused
by heavy rains leading to the failure of the Highline Canal
upstream from Eighth Avenue and Hanibal Drive. Several
basements and streets were flooded as a result.

Location

Drainage Area (sq. mi.)

1.46
1.02

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For purposes of this study, the drainage basins were considered
to be fully developed, consistent with the comprehensive
land use plans of the City of Aurora. Complete development,
for the most part, exists today and includes residential develop-
ment with some commercial development along Colfax Avenue.
Development plans also call for two large industrial parks, one
south of Sixth Avenue in the Granby Ditch Basin and another
east of Chambers Road in the Sable Ditch Basin. The proposed
Sixth Avenue industrial park has not been developed. The
warehouse district located approximately one half-mile east
of Chambers Road, north of Colfax Avenue, has been completed.
Sable Ditch runs through this warehouse district. Buckley
Air Base, in the upper reaches of both basins, is presently
considered undeveloped. Because this facility is a federal
military reservation, there are no plans for future development.
A major portion of both basins is planned for residential with
high density residential areas located generally south of
East Sixth Avenue and immediately east of Interstate Highway 225.

FLOOD RELATED STUDIES AND OTHER PERTINENT DATA

One previous hydrology study was completed for Granby Ditch
by the City of Aurora as a part of the Granby Ditch improvement
design. The Rational Method was use~ in that study utilizing
a runoff coefficient of 0.4 in computing lOa-year peak discharges.
As that study was part of the Granby Ditch improvement design,
the effect of a proposed detention pond to be located upstream
from Sixth Avenue was considered. This pond was designed to
contain all of the laO-year flood generated above Sixth
Avenue. Funds needed to complete this proposed pond have
not yet been allocated and only a small portion of the right-of-way
required has been purchased.