FLOOD10420

• County: Adams
• County: Broomfield
• County: Weld
• Community: Broomfield, Westminster and Thornton
• Stream Name: Lower Big Dry Creek
• Title: Lower Big Dry Creek Hydrology Study
• Date: 6/1/2005
• Prepared For: Big Dry Creek Watershed Association
• Prepared By: Wright Water Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Lower Big Dry cpreek Hydrologic Study

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immediately, increasing deterioration of the watershed will occur. Without a
proactive vision towards the future, dJmage will be more frequent and severe.

. Further information must be cOllectek on erosion impacts and sediment loading
in stream segments in the waters hid. This information will be useful when
reviewing future development plans qnd issuing development permits. This will
be completed as part of the Army (Jorps of Engineers Watershed Study [a $3
million effort).

Rich Muzzy of Pikes Peak Regional Council of Governments noted that the drainage criteria
used in the plan are based on the existing Jainage criteria for each of the individual agencies
involved. To address the issues of jurisdi+Ona! boundaries, a matrix of the relevant design
criteria from each entity was compiled to determine the best strategy for the entire watershed.
The design criteria in the Plan are based In typical drainage requirements of limiting peak
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discharges to existing conditions (Personal Communication with Rich Muzzy, Pikes Peak
Regional Council of Governments).

7.2.2 Bear Creek and Chatfield Reservoir Watersheds

Russ Claysbulte, watershed coordinator for le Bear Creek Reservoir and Chatfield Reservoir
watersheds, was contacted regarding stream restoration work in these watersheds. Phosphorus
control regulations are in place in these watersheds. Studies have shown that a single storm
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event can contribute as much as 2,000 pounds of phosphorus. Streambank stabilization helps to
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reduce this loading; therefore, there has beenl interest and funding for streambank stabilization to
help entities comply with the phosphorus control regulation.
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In the Bear Creek watershed, Coyote Gulch has experienced significant erosion with incised
banks as high as 35 feet due to upstream deJe10pment. About 1/8 of a mile was stabilized at a
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cost of about $400,000 under a partnership with UDFCD, non-point source funding and Jefferson
County. From a water quality perspectivel approximately 1,200 pounds/year of phosphorus
loading is projected to be reduced by contrbUing erosion. This reduction was a key "driver"
enabling funding of the project (Personal Codununication with Russ C1ayshulte).

971-179.092
June 2005

In the Massey Draw area of the Chatfield Reservoir watershed, substantial downcutting and
erosion was present and has undergone restofation. About 1/3 mile was restored with cascading
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Wright Wa'ter Engineers, Inc.

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