FLOOD10420

• County: Adams
• County: Broomfield
• County: Weld
• Community: Broomfield, Westminster and Thornton
• Stream Name: Lower Big Dry Creek
• Title: Lower Big Dry Creek Hydrology Study
• Date: 6/1/2005
• Prepared For: Big Dry Creek Watershed Association
• Prepared By: Wright Water Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Lower Big Dry Creek Hydrologic Study

5.0 OVERVIEW OF DRAINAGE AND FLOOD PLANNING AND POLICIES IN THE

BIG DRY CREEK VlIATERSHED

In addition to the hydrologic studies conducted by the BDCW A, all of the cities and counties in
the watershed, with the exception of Weld County, are members of the Urban Drainage and
Flood Control District (UDFCD) and participate in regional storm drainage and flood control
planning and have generally adopted the storm drainage criteria developed by UDFCD (UDFCD
1999,2001). Weld County is not located within the urbanized metro Denver area; therefore" it is
not within UDFCD's planning boundary. The Federal Emergen?y Management Agency (FEMA)
has, however, mapped floodplains in Weld County, in addition to the upper portion of the
watershed. The discussion below describes the current approach and extent of stormwater
management and planning in the urbanized portion ofthe watershed, as well as in Weld County.

5.1 Current Approach to Stormwater Management, Policies and Criteria in
Upstream Cities

The cities and counties within UDFCD's boundaries in the watershed have all adopted UDFCD's
Urban Storm Drainage Criteria Manual (Volumes 1-3) as their criteria for stormwater
management. Volumes 1 and 2, which focus on drainage planning and design criteria, were
originally issued in 1969 and updated in 2001. Volume 3, which focuses on stormwater quality
and erosion, was originally issued in 1992 and updated in 1999. The UDFCD criteria set the
regional standard for the metro Denver area. UDFCD's policies are founded on twelve key
statements that lay a s,trong foundation of stormwater management. These twelve statements are
quoted directly below because of the sound guidance that they provide to this project:

1. Drainage Is ,~ Regional Phenomenon That Does Not Respect the Boundaries
Between Government Jurisdictions or Between Properties. This makes it
necessary to formulate programs that include both public and private
involvement. Overall, the governmental agencies most directly involved must
provide coordination and master planning, but drainage planning must be
integrated on a regional level if optimum results are to be achieved. The ways in
which proposed drainage systems fit existing regional systems must be quantified
and discussed in the master plan.

2. A Storm Drainage System Is a Subsystem of the Total Urban Water Resource
System. Storm water system planning and design for any site must be compatible

971-179.092
June 2005

Wright Water Engineers, Inc.

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