Bank Stabilization



Bryan W. Kohlenberg, P.E.
Project Engineer, South Platte River Program

Photos of weir/jetty constuction project on South Platte River near 152nd Avenue in Adams County:

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Before Construction

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During (note constructed weir)

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1-Year After (looking downstream)

In the spring of 1997 the District designed and constructed a bank stabilization project employing the concept of bendway weirs (i.e. rock jetties). Since the traditional bank regrading method would have required removal of mature cottonwood trees along the eroding bank, the weir concept was tried for bank stabilization (see 1997 Flood Hazard News for design details). The final construction cost of the five weirs, spaced at approximately 100 foot intervals over 600 feet, totaled $43,000 or $72 per foot of bank.

Photos of the project area at about 152nd Avenue in Adams County are shown before, during, and 1-year after construction. Since construction we have observed:

No noticeable damage to weirs during two high-flow seasons (maximum 9000 cfs in July 1998).
Development of stable scour holes at ends of weirs.
No further movement of the vertical bank.
Some natural sloughing of vertical bank between weirs.
Continued sediment, woody debris, and trash deposition between weirs adjacent to the bank.
No noticeable damage to existing cottonwoods.
Strong growth of live-staked and volunteer willows and other wetland vegetation along lower bank, weirs, and newly-formed sandbars.

So far this alternative bank stabilization method at this location appears successful. In 1999 we hope to extend the project downstream by constructing an additional four weirs. We will continue to monitor the project over the next several years and report back.


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