FLOOD06564

• County: Boulder
• Community: Boulder
• Stream Name: Goose, Wonderland, Elmer's Twomile, 2-mile, 4-mile
• Basin: South Platte
• Title: Major Drainageway Planning Volume 1, Part B
• Date: 4/1/1969
• Prepared For: Boulder County
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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In urban drainage there are two storm runoff systems. The first is
the major drainage system which is that route taken by flood waters
whether or not drainageways have been planned or designed and whether
or not buildings and other improvements have been situated wisely in
respect to the drainageways. In the Denver Region the major drainage
system should be reviewed and designed on the basis of storm runoff
which would occur once each 100 years, The second system is what is
known as the initial drainage system, The initial drainage system
generally consists of a combination of storm sewers, streets, curbs
and gutters, and other facilities sized to carry the storm runoff
which can be expected about once each two to ten years. The initial
drainage system is that which drains off snowmelt runoff, the more
frequently expected storm runoff, and reduces street maintenance and
construction costs. Poorly functioning initial systems are the ones
which account for the great majority of drainage complaints to the
city or county engineer, This master planning report deals only with
the major drainage system. The major system is that which provides
the major damage and loss of life prevention function, and which provides
outfall points for the storm sewer systems.

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STUDY AREA

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This Report provides a master plan for major drainage in the urban and
urbanizing area of North Boulder ranging generally from the hogback on
the east to Boulder Creek on the west and from North Street on the south
to the divide lying north of Fourmile Canyon Creek.

The objective of the original assignment as stated in the agreement
dated October 3, 1968, was to develop master plans for three channels
Goose Creek, Twomile Canyon Creek and Fourmile Canyon Creek. After the
study was undertaken it was determined that two additional basins exis-
ted which were primary trouble makers in regard to storm drainage
problems. These two channels were Wonderland Creek and Elmer's Twomile
Creek. The consultant included these additional two basins in the scope
of work. Therefore, master plans have been developed for five water-
ways in the study area:

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Goose Creek

Elmer's Twomile Creek

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Wonderland Creek

Twomile Canyon Creek

Fourmile Canyon Creek.

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These waterways are in poor condition, ranging from having very small
flood flow capacities to being non-existent in places, The deteriorated
condition of these waterways has been a result of channel filling and