FLOOD05425

• County: Delta
• Community: Delta
• Stream Name: Gunnison, Uncompahgre River
• Basin: Gunnison
• Title: City of Delta Confluence Park Project
• Date: 10/1/1989
• Prepared For: Delta
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

1989 by the Sacramento District Corps of Engineers at the
request of FEMA. The flood plain delineations utilizing the
revised flow-frequency values have not be~n prepared. The
flood plain delineations which were revised in 1989 by the
Sacramento District, utilized the Gunnison :River peak flows
as shown in the 1983 FEMA report (old hydrology), as
requested by FEMA.

The peak flows of the Uncompahgre River have not been
revised, and there are no plans presently;by FEMA to restudy
them. If implemented, the AB Lateral project, impacting
mainly the Uncompahgre River, would not a~fect the peak
flows, according t,o the engineering cons\1~tant for that
project. When the flows in the uncompahgre River approach a
flow rate which would promote disturbance :of the armor layer
of the UncompahgrE River (2,000 cfs according to the
consultant), the flows diverted through tfje Gunnison Tunnel
would be reduced as needed to avoid such downward scour.
The 2,000 cfs flow rate is less than the ~eak flow for the
10-year flow rate of 3,100 cfs. The effedt of Ridgway
Reservoir on the reak flows would be relatively
insignificant according to Bureau of Reclama'tion officials,
since the reservoir was built for storage, not for flood
control.

Streamflow records have been maintained on the Gunnison
and uncompahgre Rive,rs in the vicinity of Delta as shown
below:

GAGING STATION RECORDS

Location Drainaqe Area

Period of
Record

#09144250, on the 8unnison
River, just upstream of the
Highway 50 bridge 5,628 sq.mi,

May 1976 -
present

#09149500, on the uncompahgre
River, 1.1 mi upstream
from the mouth 1,129 sq.mi.

1903 - 1931
1938 - present

A flow-frequency tabulation for both the Gunnison and
Uncompahgre Rivers follows:

4