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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4

model demonstration on January 18. The UOFCD representatives expressed concern
that flows over the downstream embankment crest might attack the right bank of the
river due to the flow direction of water over the crest In the model.

They suggested a second model configuration to change the downstream crest to a

V-shape, a horseshoe or straight across so that water overtopping the crest would

flow directly downstream. The present design would Include right bank rlprap

protection with the present model configuration. Ben Urbonas further suggested

consideration of the boat chute In the middle of the embankment rather than on the

west bank.. This, however, has been vetoed by white water boaters.

During the dIscussIon that followed, Cl1ff Pugh of the USBR and Ron Rossm111er of
WWE made the follOWing points on the pros and cons of these two suggestions.
1. The present downstream embankment configuration now has good flow lines. w
The current runs parallel to the crest at lower flows and angles towards the
west bank at higher flows. Both patterns naturally lead boaters to the next
chute. From 100 to 800 cfs, he flow velocIties are such that boaters can slOWly
paddle away from the downstream crest to line up with the second chute or they
can stay In the first pool If they so desire.
2. A straight or sl1ghtly curved crest at rIght angles to the channel banks would
direct the flow downstream of the embankment crest parallel to the river banks
or towards the center of the river. As a note, WWE discussed reducing the
angle of the downstream embankment crest with the river bank to reduce the
erosion potential with Cl1ff Pugh last December. The conclusion reached was