FLOOD00734

• Designation Number: 213
• County: Adams
• Community: Thornton
• Stream Name: Brantner Gulch and Tributaries
• Title: Flood Hazard Area Delineation - Brantner Gulch and Tributaries
• Date: 1/1/1983
• Designation Date: 5/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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1

SUMMARY

due to the conveyance of the flows by the designated channels

of Brantner Gulch and Regional Park Tributaries. The reader

must be aware that a lOO-year storm would cause additional

localized flooding due to concentrations of runoff at various

locations throughout the City and County. Many of these

locations would not be associated with the flooding along the

gulches. For this reason, the report cannot be presumed to

delineate all areas of flood hazard within the studied basins.

Supportive data, including water surface elevations, flood

depths and velocities, rainfall and runoff parameters, and

other technical information are also presented. Section VII

contains a narrative on the nature of the flood hazard along

each of the channels.

This report illustrates the fact that a major flood hazard

exists along the studied channels. As such, the report

presents the initial step in enabling the Urban Drainage and

Flood Control District, the City of Thornton, Adams County, and

the local property owners to understand and to deal with this

potential flood damage.

Presented in this volume is information regarding the

potential flood hazard on Brantner Gulch and its tributaries in

Thornton and Adams County, Colorado, and on Regional Park

Tributaries North and South in Adams County, Colorado. The

information is presented in the form of maps, tables, figures,

and photographs which illustrate the anticipated flooding which

would result from a lOO-year storm (a storm event which would

have a one percent chance of occurring in anyone year). The

report assumes the land in the drainage basin to be fully

developed based on future planning guidelines provided by the

City of Thornton and Adams County. The channels themselves are

considered to be in the same general condition which exists in

1982. Consequently, the predicted flooding is greater than

would actually occur at present, since only small portions of

the basin are presently developed.

Generalized presentations are made on the evaluation of

rainfall and runoff characteristics (hydrology) and the deter-

mination of the depth of flooding (hydraulics). These analyses

have made possible the preparation of fifty Flood Hazard Area

Delineation Sheets (FHAD Sheets) which are the essence of this

report. Through use of these sheets, a reaaer may determine

which properties are anticipated to be inundated by a lOO-year

flood event. The illustrated flooding is that which would occur