FLOOD00144

• County: Logan
• Community: Crook
• Stream Name: South Platte River
• Title: Reconnaissance Report for a Flood and Erosion Control Project
• Date: 12/1/1985
• Prepared For: Logan County
• Prepared By: CWCB
• Floodplain - Doc Type: Project

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These discharge valves were used to determine water surface
level as presented by profiles as presented on plates 6 and 7.
These profiles illustrate the water surfccce levels for a
respective flood event, The CWCB has reviewed the profiles as
prepared by CDOH, using the HEC - 2 routing procedure, and finds
the data to be acceptable for a reconnaissance level
investigation.

J

Analysis of the river hydraulics, shows that the left bank
levee (North) has a varying degree of flcod protection, At a
number of locations the top of dike is at the 100 - year flood
elevation; therefore, improvements are required to the existing
system to provide an adequate degree of flood protection to
Crook. Due to the inconsistency of float protection of the North
bank levee, it is assumed that the systU\ will fail at a 10- year
flood event.

Within the existing dike system, tho erosive forces of
floodwaters are transmitted to the North streambank throughout
the study reach.

PLAN FORMULATION

In the formulation of a plan-of-imp:'ovement for the study
reach the following concerns and issues \~re considered by the
CWCB.

o

Floodplain Encroachment
Flooded Areas
Erosion of Streambank and Dikes
Location of Tieback levee
Ground water Problems
Channel Sedimentation

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Floodplain Encroachment

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Within natural floodplains two flow conveyance zones
exist. These zones are commonly referre~ to as the floodway
flood fringe area. The floodway is the :low path needed for
passage of floodwaters without back-up o~ flow change
effects, It conveys the largest portion of floodflows,
the flood fringe zone represents the outer limit of the

and
the

Whereas,

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