FLOOD04971

• Designation Number: 4
• County: Boulder
• Community: Boulder County
• Stream Name: Left-hand Creek
• Basin: South Platte
• Title: FIR - Left-Hand Creek - Volume I
• Date: 1/1/1969
• Designation Date: 5/1/1969
• Prepared For: Boulder County
• Prepared By: USACE
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Ob5Tr~ctron5 to FlOod Flow
The bridges present the main obstructions to the flood.
In general, the water surface upstream of the bridges would be
several feef higher than it would be if the bridges were not in place.
This backwater effect is usually dissipated in less then 1,000 feef
upstream ot the bridges due to the steep bod slopes. The diversion
dams also alter the channel characteristics by raising the channel
bed upstre~ and lowering the bed downstream of each structure. Tho
effects ef the raised bed decreases with increased flows so that the
stages for major floods are more dependent on the $i~e ef opening
through tho dams. The diversion dams de not significantly obstruct
tho flews.

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