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FLOOD01787
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Last modified
11/23/2009 12:58:08 PM
Creation date
10/4/2006 10:21:40 PM
Metadata
Fields
Template:
Floodplain Documents
County
Boulder
Stream Name
South Boulder Creek
Title
South Boulder Creek/ Flatirons
Date
12/5/1997
Prepared For
Boulder
Prepared By
Consultants
Floodplain - Doc Type
Community File
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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />SECTION I <br /> <br />SUMMARY <br /> <br />INTRODUCTION <br /> <br />In 1977 the U.S. Army Corps of Engineers (Corps) conducted a hydrology study <br />that included the South Boulder Creek Basin. That study provided the hydrology for <br />the Urban Drainage and Flood Control District (UDFCD) Flood Hazard Area <br />Delineation (FHAD) and the Federal Emergency Management Agency (FEMA) Flood <br />Insurance Study (FIS) and Flood Insurance Rate Maps (FIRMs) for South Boulder <br />Creek. <br /> <br />In 1996, Love and Associates identified that South Boulder Creek could spill greater <br />flows than identified in the FHAD and that these spills could travel to the west side <br />of the valley and overtop Highway 36, largely west of Foothills and thus posed a <br />hazard to the neighborhood north of 36. <br /> <br />Phase I effort reviewed the FHAD and Love's investigation, and identified 100 year <br />spills on the order of 2700 cfs from South Boulder Creek above Highway 36. The <br />spill was shown to commingle with local drainage from the Dry Creek Ditch No. 2 <br />and the Viele watershed. The Phase I effort obtained a copy of the Corps' <br />hydrology model to identify the timing of the Viele inflows and allow simplified <br />simulation of its drainage network. Some general problems were noted in the <br />Corps' model, but our effort focused on the determination of how much of the <br />South Boulder Creek spill would return via Viele and how much would continue to <br />the West Valley spill route. Phase I determined that about 1800 cfs would <br />continue to the West Valley north of Highway 36. <br /> <br />The Urban Drainage and Flood Control District (UDFCD) authorized this Phase II <br />initial hydrology study to estimate the distribution of flooding in West Valley <br />downstream of Highway 36 to the area of the Wellman Ditch. For the purposes of <br />the Phase II study the Corps' hydrology remained unchanged upstream of Highway <br />36 other than modifications to better reflect floodplain routing downstream of the <br />mountains. All new basins and routing elements were inserted for the Viele Basin <br />and the area downstream of Highway 36. <br /> <br />Also, since questions regarding hydrology had been raised by the local governments <br />and our work, requests of the Corps were made to obtain background data, basin <br />mapping, and verification studies. <br /> <br />I - 1 <br />
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