FLOOD03543

• County: Arapahoe
• Stream Name: South Platte
• Basin: South Platte
• Title: Union Avenue Boat Drop
• Date: 1/1/1983
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Easement

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MEMORANDUM

TO: Nick Ioannides, ewcs
FROM: Wright Water Engineers, Inc.

DATE: April 13, 1989

SUBJECT: Union Avenue Boatchute Model

Observations of the boatchute I!Odel at the USSR laboratory were made by
Robert Ferguson (WWE) on April 12 and April 13, 1989 at the request of the
USSR staff. The USSR staff was in the process of performing the sediment
study portion of the IlOdeling effort. The model was being operated at a
river flow rate of 3,000 cfs. Sand was fed at a pOint upstream of the
Union Avenue bridge at rates determined from COE sediment transport studies
for this reach of the South Pl atte River. At the time of these
observations the sediment test had run for 19 hours. A state of
. equilibrium had not yet been reached. Wave" form dunes had formed in the
first pool bottom. However, they were regular in form rather than the
bro~en form expected at equilibrium. USSR personnel feel another 4 hours
of operation would be sufficient.

Observatf ons

1. A delta formed on the downstream face of the eOE dam crest. Top
elevation of this delta is below the pool tailwater elevation.
This delta extends downstream approximately 40 feet at which point
it drops off sharply to the normal pool invert. The delta does
not affect the flow patterns over the COE dam crest at 3,000 CFS.

2. A sandbar formed alon9 the upstream face of the new embankment
downstream of the existing dam. This sandbar is constantly
changing. It builds and then scours. This deposition tends to
encourage flow toward the left side downstream boatchute.

3. The upstream inlet channel for the Englewood intakes is free of
sediment. USSR personnel have IlOdeled the solid wall as discussed
at the last sponsors meeting. This wall allows inflow to the
intake chute only at its upstream end. It was reported that when
the sediment flows first started, sediment built up in the
upstream end of the channel where the first two intakes are
located. This is similar to what happens now according to
Englewood personnel. This deposition however, flushed out with

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