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• Board Meeting Date: 11/19/2008
• Description: CF Section – En-bloc Non-Reimbursable Investments - NOAA Atlas 2 Precipitation Atlas Update
• Board Meetings - Doc Type: Memo

Water Project Construction Program - Project Data
Non-Reimbursable Investment
Grantee: County:
Colorado Water Conservation Board Statewide
Project Name:
NOAA Atlas 2 Precipitation Atlas Update
Project Type
: Update of Statewide Precipitation A tlas Providing Point Precipitation Values
Statewide for Various Return Frequencies and Durations
Drainage Basin: Water Source
All River Basins in Colorado : N/A
Total Project Cost Funding Source
: $900,000 : CWCB Const.
Fund
Type of Grantee Median Household income
: State Government : N/A
CWCB Non-Reimbursable Inv.: Interest Rate
$300,000 : N/A Term: N/A
Floodplain delineations and design of hydraulic stru ctures must use design point rainfall as a
basic data input. Currently, the tool most commonly used is the Precipitation Atlas prepared in
1973 by the National Oceanic and Atmospheric Admi nistration (NOAA), generally referred to as
the NOAA Atlas 2. The NOAA Atlas 2 uses isohyetal figures to por tray design rainfall depths
for the entire State of Colorado for return fre quencies ranging from 2-year to 100-year and for
durations of 5 minutes to 24 hours. While this A tlas is very useful in obtaining the data needed
for hydraulic designs and floodplain an alyses, at 35 years old, it is widely regarded as being out
of date. Accuracy is critical for this informa tion, as it will help mitigat e “overdesigns”, which
needlessly increase design costs, or “underdesigns”, which increase th e threat to public safety. It
is also critical for the accurate portrayal of fl oodplain delineations, which are not only the most
reliable risk identification tool for flood threats, but also have important ramifications for landuse
decisions, local regulations, and insurance costs and mandatory purchase requirements.
This request is to provide funds for the pur pose of updating the long out-of-date NOAA Atlas 2
for the State of Colorado. NOAA is currently performing work around the country in groups of
states with the goal of updati ng design precipitation data thro ughout the nation. By grouping the
states together in group s of projects, NOAA is able to a ttain benefits of scale and bring
additional partners into the projects. Initially, NOAA proposed grouping Colorado with
Wyoming and Montana. However, because Montan a is unable to provide funding for their share
of this grouping, this project could not move forward. As such, NOAA issued a new proposal
with Colorado grouped with six Midwestern states that have funding availabl e but are in need of
a seventh state in order to move forward accord ing to NOAA policy. As such, this project will
be able to move forward at this time if Colorado can commit the funds.
According to NOAA, the update process will take 2-3 years, at which point, updated design
rainfall information will be available for use th roughout the State of Colorado. NOAA states that
due to the limited period of reco rd used in the original Atlas, completion of this project will
nearly triple the supporting data inherent in the results port rayed in the updated Atlas.
This request represents the entire share needed fo r completion of this project. This is a one-time
project request, and no further appl ications will be submitted in the future for additional funding.
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