FLOOD03253

• County: Boulder
• Community: Boulder
• Stream Name: South Boulder Creek
• Basin: South Platte
• Title: South Boulder Creek Draft Hydrology Study Phase III
• Date: 2/10/2000
• Prepared For: UDFCD
• Prepared By: Taggart Engineering Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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4. Calibrating the model to the 1969 flood or at least comparing for
reasonableness, and spot checking major basin runoff using the UDFCD
Colorado Unit Hydrograph Procedure (CUHP) for reasonableness. Also
review of the Eldorado stream gage data is included. Efforts to review the
Eldorado gage data and calibrate to the 1969 flood are limited.

5. Preparing basin and model maps, and model documentation such as
representative hydrographs and discharge profiles.

6. Agency contact (USACE, USGS, CWCB, NRCS, City, County, Denver
Water),

7, General characterization of flow timing, magnitude, and distribution in the
South Boulder Creek floodplain below Highway 93.

8. Specific review and effort to comply with CWCB and FEMA requirements.

9. Summary report and technical appendices.

What is not required: Snowmelt hydrology, ifi' tion testing, reservoir operations
or storage statistical analysis, long-term rain alh off modeling or statistical
analysis using NWS or other long-term rainfal ecords, extensive field surveys,
floodplain storage routing, rain gage statistical analysis, hydraulics and split flow
analysis beyond specific limits, floodplain hydraulic modeling or mapping.

MODIFICATION OR DEPARTURES FROM SCOPE

As with any study, the investigation raises facts and issues which inevitably lead to
modification or departure from the scope. Some of these are as follows:

1. Rainfall. Contacts with NOAA were both helpful and led to some dead ends.
We attempted to get better guidance on arranging the temporal (time) pattern
of the critical rainfall, and two of the references indicated didn't lead to
fruitful results. UDFCD provided consultation with John Henz, meteorologist
which provided helpful guidance. We attempted to use a storm pattern he
suggested, but were unable to satisfy NOAA statistics. Henz suggested
providing a custom rainfall analysis of the UDFCD network and providing
design storms that were locally based, but this would require substantial
funding and likely depart from NOAA based documentation, so the sponsors
decided to not proceed beyond the TEA analysis herein.

2. Eldorado Stream Gaqe Data. The research revealed that the Eldorado Stream
Gage had a substantial record of daily flows and was primarily used for
management of water distribution to irrigation ditches. While peaks had

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