FLOOD10136

• Designation Number: 114
• County: Chaffee
• Community: Poncha Springs
• Stream Name: South Arkansas River/Poncha Creek
• Basin: Arkansas
• Title: FIR - South Arkansas River/Poncha Creek, Poncha Springs, CO
• Date: 3/1/1978
• Designation Date: 11/1/1978
• Prepared By: WRC, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Therefore, upon official approval of this report by the Colorado

Water conservation Board, the areas described as being within the 1%

, *
chance flood (lOO-Year Flood) can be designated as flood hazard areas

and their use regulated accordingly by the local agencies.

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6. Preparing a technical addendum containing pertinent data related
to the hydrologic and hydraulic analysis.

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7. Preparing a floodplain information report.

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Mapping and Surveys

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Purpose and Scope

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Chaffee County in cooperation with the Colorado Water Conservation

Board obtained recent topographic maps for this study. This mapping was

prepared by Delta Aerial Surveys, Inc. under a separate contract.

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The purpose of this study is to develop a planning tool that can

be used by the Town of Poncha Springs and Chaffee County to regulate the

land use of areas within the floodplain of the South Arkansas River and

Poncha Creek in order to minimize flood damages and provide protection

of both human life and property.

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Specific topographic data provided to the consultant includes:

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The scope of the study includes:

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1. Two reproducible mylar planimetric-topographic map sheets both
having a contour interval of 2 feet. The scale of the first is
l",~ 200", while,the second has a scale of 1" ~ 400'.

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1. Collecting available basic data related to this study from

different sources including local, state, and federal agencies.

2. One set of 9" x 9" black and white photographic contact prints.

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3. One set of Xl and GR cards (HEC-2 Computer Program) for 25
digitized cross sections of the South Arkansas River Valley.
A printout of the digitized cross sections was also supplied.

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2. Conducting field surveys as needed to augment the basic data
already available.

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The items listed above are available to the Colorado Water Conserva-

tion Board. Reproducible mylar for the topographic maps with a scale of

1" ~ 200' and 1" ~ 400' are available to the Town of Poncha Springs and

Chaffee County. In addition to the above information, the Colorado Water

Conservation Board has provided cross section information for Poncha

Creek. This information was secured through actual field surveys performed

for a number of cross sections within the study reach.

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3. Researching and documenting the history of significant flood

events that have occurred in the vicinity of the study area.

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4. Performing hydrologic analysis to determine the peak rate of

runoff for the 10-, 50-, 100-, and SOD-year frequency flood

discharges in the study reaches.

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5. Performing hydraulic calculations within the study reach to
determine the water surface profiles for the 10-, 50-, 100-,
and 500-year frequency flood and to delineate the 100-year
flood in plan.

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Acknowledgments

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* The terms "1% Chance Flood", "Intermediate Regional Flood", and "100-
Year Frequency Flood" can be used interchangeably as they are defined
by the same type of flood event (see Glossary). However, for consis-
tency, wherever possible the term "1% Chance Flood" will be used in
this report.

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We wish to acknowledge the assistance and cooperation of the agencies,

firms, organizations and individuals listed below. Many city and county

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