FLOOD05835

• County: Arapahoe
• Stream Name: South Platte
• Basin: South Platte
• Title: Union Avenue Boat Drop - Boatchute Model Operation
• Date: 2/2/1989
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Project

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model demonstratlon on January 18. The UDFCD 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 riprap

protectlon 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, C11ff Pugh of the USBR and Ron Rossmlller 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 Cllff Pugh last December. The conclusion reached was