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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Table-3 lists the water surface elevations for the 10-, 50-, 100-,

and 500-year flood events at the various cross section points.

elevations can be conveyed to the ground. Two monuments, identified as

PS 1 and PS 2. have been established in the field for this purpose. An

example of the reference monument is presented below.

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Flooded Area

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In Colorado, the 1% chance flood has been selected to delineate and

regulate floodplains. Therefore. the flooded area maps show the boundary

of the 100-year floodplain. The mapping has a 2 foot contour interval

and a scale of 1 inch equal to 200 feet. The limits of the 500-year flood

are also shown on the flooded area maps. If needed. the 10- and 50-year

floods could be readily delineated on these maps using the information

presented in Table-3.

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The 100-year floodplain. as delineated on the flooded area maps. meets

the requirements of House Bill 1041. Upon official approval of this report

by the Colorado Water Conservation Board, the area outlined by the 100-year

flood boundary will be designated as a floodplain area and the local offici-

als may regulate it accordingly.

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Flood Elevations

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The water surface elevations for the 10-, 50-, 100-, and 500-year floods

can be found in four different locations throughout this report. These loca-

tions include: (1) the flood frequency elevations presented in Table-3 for

the selected points along the river reaches; (2) the limits of the 100-year

and 500-year flood in plan presented on Plates 3 through 6; (3) the flood

profiles shown on Plates 7 through 11; and (4) the water surface elevations

for the different frequencies at typical cross sections throughout the

study reach shown on Plates 12 through 20.

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x<(~}- CO&
.:t:'Yt PS 2 ~
() + -<
ELEV.
7504.43 {\I.o
,Q)

Detail of Monument Cap.

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Reference Monument PS-2. located near the powerpole at the intersection of
True Avenue with Limit Street. is within the small circle of rocks at the

feet of the engineer.

areas where controversy arises over the

The flood profiles may be used in
1% flood boundary on the flooded area

plates.

Since the flood profiles give
a known point, the high water

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the elevations and distance or stationing from

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