FLOOD10402

• County: Douglas
• Basin: South Platte
• Title: Douglas County, Colorado Flood Warning Assessment - Project No. CI03-037
• Date: 9/1/2004
• Prepared For: Douglas County Public Works, CWCB, Parker Stormwater Utilities, Castle Rock Stor
• Prepared By: HDR
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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HR

Douglas County, Colorado Flood Warning Assessment -
Executive Summary

HDR
Denver, Colorado

HDR performed a flood warning assessment for Douglas County, Colorado with the
main focus of the assessment being on the Cherry Creek and Plum Creek drainage
basins (project area) including the population areas of Larkspur, Castle Rock, Sedalia,
Louviers, Franktown and Parker. The project was performed under the guidance of
Douglas County Engineering (County).

Multiple tasks were accomplished in order to perform the assessment and are described
in detail in the Final Project Report and Technical Addendum that accompanies the
report. A description of these tasks are described as follows. Interviews were held in
order to obtain an inventory of existing response agencies, flood detection resources,
flood prediction resources, flood warning resources, and communications resources
involved in flood related actions and activities within the project area. Existing
hydrologic/hydraulic. information within the project area was obtained and reviewed for
the purpose of identification of potential flood hazard areas. A web site was developed
that contains weather information that is currently available on the Internet and is
applicable to Douglas County. A flood orientation was held for Douglas County
agencies/departments that demonstrated the existing weather detection, prediction and
warning resources within Douglas County.

All the information that was gathered on the response agencies, Incident Command
System, flood detection resources, flood prediction resources, flood warning resources,
communications resources, potential flood hazard areas, and hydrologic/hydraulic
characteristics of the watercourses were reviewed and evaluated. Recommendations
were made to enhance these components, if it was felt that if the recommended
enhancement was implemented, the benefit would outweigh the cost associated with the
implementation of the recommendation.

One of these benefits would include a higher rating by Federal Emergency Management
Agencies Community Rating System resulting in lower flood insurance rates for
residents and business located within FEMA defined 1 DO-year floodplains. Other
benefits would include more accurate prediction of flooding events, increased lead time
of flooding events, and pre-defined knowledge of areas at risk from flooding, possibly
resulting in a reduced threat of loss of life.

The following are a summary of the key recommendations made in the final project
report:

1