BOARD01367

• Board Meeting Date: 3/16/2004
• Description: CWCB Director's Report
• Board Meetings - Doc Type: Memo

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Modeling System to model and evaluate 2003-2004 operations, This project is the most
comprehensive study in recent years in Colorado,

Floodplain Map Modernization: The first two countywide Digital Flood Insurance Studies
prepared as part of the Colorado Map Modernization Program have been presented to FEMA in
preliminary form, These studies are the first studies prepared for Colorado counties under the
supervision of an agency other than FEMA, The study for the City and County of Denver was
prepared under the direction of the Urban Drainage & Flood Control District (UDFCD) and the
study for Douglas County was prepared under the joint direction of CWCB and UDFCD, A
third study, for Boulder County, will begin shortly, under the direction of CWCB, The hope of
the UDFCD and CWCB staffis that the success of these projects will demonstrate the value of
state and regional management of Map Modernization projects in Colorado, Both the Denver
and the Douglas County projects included 80 percent FEMA funding, 10 percent CWCB
funding, and I percent local and regional funding,

Floodplain Map Modernization Business Case Plan: On Mar, I we completed the Flood Map
Modernization Business Case Plan (BCP) for Colorado, The BCP report was funded through a
grant from FEMA, using a 25 percent matching contribution.

The report provides technical and financial details for preparing digital countywide floodplain
maps for all 64 counties in Colorado as part ofthe national Map Modernization program, Prior
to the start of Map Modernization efforts in 2003, work was conducted on digital Flood
Insurance Studies in five counties, Flood Insurance Studies for three counties are either in
progress or just completed with FY 2003 funding, CWCB has received informal approval from
FEMA for four more counties in FY 2004. That would bring the total number of counties where
studies are proposed in the immediate future, currently in progress, or complete to 12 of 64
counties, CWCB staff will update the BCP annually during the five years of the Map
Modernization Program (FY 2004 to FY 2008),

Post-Wildfire Flood and Debris Flow Hazards: The CWCB continues to participate in the
development of technical information for high priority areas of Colorado where wildfires during
the summer of 2002 devastated thousands of acres of forest lands, The USGS, under contract
with FEMA and with technical advisory and review assistance from the CWCB, has developed
post-wildfire flood and debris flow hazard information within the Hayman, Coal Seam, and
Missionary Ridge burn areas,

The work involved new hydrologic models to predict floodwater nmoff for the partially and fully
burned basins, Hydraulic models for the priority riverine stream reaches (for example, the South
Platte River in the vicinity of Deckers and Mitchell Creek in the vicinity of Glenwood Springs)
were then developed by the USGS to compute flood profiles for the 100-year post wildfire
condition, which led to post-wildfire floodplain delineations using the best available topographic
data and base mapping for the area of interest. FLO-2D models were generated specifically
within the Missionary Ridge and Coal Seam bum areas to predict debris flow hazard areas on
alluvial fans, Flood and debris flow hazard information for all three bum areas is available for
review from the CWCB,

In addition to the USGS work, Douglas County selected and contracted with a consulting firm to
develop emergency floodplain information for several tributary streams in the Hayman Bum
area, The CWCB now plans to further assist the County with more detailed hydraulic analyses
along several tributary stream reaches using new LIDAR-based topographic data that has been
obtained by the County, The CWB also contracted with consulting firms to deliver approximate
and detailed floodplain delineations in Teller and Douglas Counties to supplement the work done
by others.

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