FLOOD03324

• County: Logan
• Community: Sterling
• Stream Name: Pawnee Creek
• Basin: South Platte
• Title: Flood Hazard Mitigation Feasibility Study
• Date: 3/1/2001
• Prepared For: Logan County
• Prepared By: ICON Engineering, Inc.
• Floodplain - Doc Type: Project

D1SCJJlJMER

.

Th" work that provides the basis of/his report wasfimded by the Federal Emergency
Managemellf Agency (FEMA), Mitigation Directorate, undu the Hazard Miligation Technical
Assistance Program (HIofl"AP) Contracl, EMW-95-C-4678, The authars are solely responrihle
for the accuracy of the statements and inlerprela/ions in Ihe reporl. Such inlerpretalions do no
necessarily reflect the views afthe Federal Government,

c..

URS GreinIN' Woodward Clyde

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TABLE OF CONTENTS

Section 1

Section 2

Section 3

Section 4

Section 5

Section 6

List of Tables

TableJ.]
TableJ-2
Table 3-3
Table 3-4
Tahle3.5

Introduction and Bat:kground.................................... ...................................................1.'
1,1 Historical Flooding and 1997 Flood E..erll..............................................!-1
1.2 Purpose of Analy~;~ ..........................................m..............m................... 1.2
I.) TasksPerfotmed..........................................................................:...........1-2
1.4 Existing Floodplain Mapping ..................................................................1-3

Proposed Mitigation Altemative...........,............................ ............................................~.1

Hydrologic/Hydraulic Review of Flood Mitigation Altema~:';~iI: ........................_....... 3-1

3.1 Hydrolog)'................................................................................................3-1
3.2 HydraulieEvaluations..............................................................................3-1
3.2.1 ?a"'li~~ CI~~:..11JIlL Stem......................................................m... 3-1
3.2.2 Pawnee Creek Overflow.............................................................. 3.3
3.2.3 Overflow at Atwood ................................m................................. 3-5

Flood Inundation Impacts..................................... ........................................................4-1

Conciuz:':'ns..............................................................................................................,...~-:

5.1 Use ofHydrologiCJHydrnulie j'.,!o<.!dinr: Con(']"~:"i,S lor Floodplain
Mapping...................................................................................................5-1

Ralerenc.~s ~nd PrevIous Study ................................................................................... 6.1

Pawnee Creek Recorded and Modeled Flows ..................................................... 3-2
Flood Elevations on the Mainstem ofPllwnee Creek: Pre. and Post.Project..... 3-4
Floodplain Widths on the Mainstem of Pawnee Creek: Pre- and Post.Project.. 3-4
Flood Elevation.> for the Sterling Overflow: Pre- and Post-Project.................... 3-6
Flood Elevations for the Atwood Overflow: Pre. and Post.Proj\"Ct ..........__....... 3-6

ListurFi~ures
Figure] Alternative 5. Pawnee CreeklRiversidc Cemetery
Figure 2 MainCh=cIProfi!es
Figure) SlcrlingOvcrfiowProfilcs
F;gw-o;:.; AlWOoJOvctfiowi'rofiics

List of Appcndices
Appendix A Hydrologic/Hydraulic Computations
AppendixB FloodplainWorkMap

IJRS GrBlner W<wdwJJrd Clyde

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