CECW-EH-D

Engineer Manual1110-2-1601

Department of the ArmyU.S. Army Corps of Engineers

Washington, DC 20314-1000

EM 1110-2-1601

1 July 1991/30 June 1994

Engineering and Design

HYDRAULIC DESIGN OF FLOODCONTROL CHANNELS

Distribution Restriction StatementApproved for public release; distribution is

unlimited.

DEPARTMENT OF THE ARMY EM 1110-2-1601U.S. Army Corps of Engineers Change 1

CECW-EH-D Washington, D.C. 20314-1000

Engineer ManualNo. 1110-2-1601 30 June 1994

Engineering and DesignHYDRAULIC DESIGN OF FLOOD CONTROL CHANNELS

1. This Change 1 to EM 1110-2-1601, 1 Jul 91:

a. Updates Chapter 2.

b. Updates Chapter 3.

c. Adds Chapter 5, which describes methods for predicting n values for the Manning equation.

d. Updates the Table of Contents to reflect the changes in Chapters 2 and 3 and the addition ofChapter 5.

e. Updates the preceding chapters to reflect the addition of Chapter 5.

f. Adds references in Chapters 3 and 5 to Appendix A.

g. Adds updated plates in Chapter 3 to Appendix B.

h. Inserts page F-18, which was inadvertently omitted.

i. Updates Appendix H.

j. Adds symbols in Chapter 5 to Appendix I.

2. Substitute the attached pages as shown below:

Chapter Remove page Insert page

Table of Contents i and ii i and ii2 2-1 and 2-2 2-1 and 2-23 3-1 thru 3-10 3-1 thru 3-125 5-1 thru 5-16

Appendix A A-1 thru A-7 A-1 thru A-8Appendix B B-35 thru B-60 B-35 thru B-61Appendix F F-17 F-17 and F-18Appendix HAppendix I

H-1 and H-2I-1 thru I-4

H-1 and H-2I-1 thru I-4

EM 1110-2-1601Change 130 Jun 94

3. File this change sheet in front of the publication for reference purposes.

FOR THE COMMANDER:

2

EM 1110-2-16011 July 1991

US Army Corpsof Engineers

ENGINEERING AND DESIGN

Hydraulic Design of FloodControl Channels

ENGINEER MANUAL

DEPARTMENT OF THE ARMY EM 1110-2-1601U.S. Army Corps of Engineers

CECW-EH-D Washington, D.C. 20314-1000

Engineer ManualNo. 1110-2-1601 1 July 1991

Engineering and DesignHYDRAULIC DESIGN OF FLOOD CONTROL CHANNELS

1. Purpose. This manual presents procedures for the design analysis and criteria of design for improvedchannels that carry rapid and/or tranquil flows.

2. Applicability. This manual applies to major subordinate commands, districts, and laboratories havingresponsibility for the design of civil works projects.

3. General. Procedures recommended herein are considered appropriate for design of features which areusable under most field conditions encountered in Corps of Engineers projects. Basic theory is presentedas required to clarify presentation and where the state of the art, as found in standard textbooks, is limited.In the design guidance, where possible, both laboratory and prototype experimental test results have beencorrelated with current theory.

FOR THE COMMANDER:

ROBERT L. HERNDONColonel, Corps of EngineersChief of Staff

________________________________________This manual supersedes EM 1110-2-1601, 1 July 1970

DEPARTMENT OF THE ARMY EM 1110-2-1601U.S. Army Corps of Engineers Change 1

CECW-EH-D Washington, DC 20314-1000

Engineer ManualNo. 1110-2-1601 30 June 1994

Engineering and DesignHYDRAULIC DESIGN OF FLOOD CONTROL CHANNELS

Table of Contents

Subject Paragraph Page

Chapter 1IntroductionPurpose . . . . . . . . . . . . . . . . . . . . . . 1-1 1-1Scope . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1-1References . . . . . . . . . . . . . . . . . . . . 1-3 1-1Explanation of Terms . . . . . . . . . . . . . 1-4 1-1Channel Classification . . . . . . . . . . . . 1-5 1-1Preliminary Investigations for Selection

of Type of Improvement . . . . . . . . . . 1-6 1-1

Chapter 2Open Channel Hydraulic TheoryPhysical HydraulicElements . . . . . . . . . . . . . . . . . . . . . 2-1 2-1

Hydraulic DesignAspects . . . . . . . . . . . . . . . . . . . . . . 2-2 2-1

Flow Through Bridges . . . . . . . . . . . . 2-3 2-5Transitions. . . . . . . . . . . . . . . . . . . . . 2-4 2-8Flow in Curved Channels . . . . . . . . . . 2-5 2-12Special Considerations . . . . . . . . . . . . 2-6 2-14Stable Channels . . . . . . . . . . . . . . . . . 2-7 2-15

Chapter 3Riprap Protection

Section IIntroductionGeneral. . . . . . . . . . . . . . . . . . . . . . . 3-1 3-1Riprap Characteristics . . . . . . . . . . . . . 3-2 3-1

Section IIChannel CharacteristicsSide Slope Inclination . . . . . . . . . . . . 3-3 3-4Channel Roughness, Shape,Alignment, and Gradient. . . . . . . . . . . 3-4 3-4

Subject Paragraph Page

Section IIIDesign Guidance for Stone SizeGeneral . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3-4

* Design Conditions . . . . . . . . . . . . . . . . . 3-6 3-5*Stone Size . . . . . . . . . . . . . . . . . . . . . . . 3-7 3-5

* Revetment Top and EndProtection . . . . . . . . . . . . . . . . . . . . . . 3-8 3-8*

Section IVRevetment Toe Scour Estimation and Protection

* General . . . . . . . . . . . . . . . . . . . . . . . . 3-9 3-9** Revetment Toe Protection

Methods . . . . . . . . . . . . . . . . . . . . . . 3-10 3-10** Revetment Toe Protection

Design . . . . . . . . . . . . . . . . . . . . . . . . 3-11 3-10** Delivery and Placement . . . . . . . . . . . . 3-12 3-11*

Section VIce, Debris, and Vegetation

* Ice and Debris . . . . . . . . . . . . . . . . . . . 3-13 3-11** Vegetation . . . . . . . . . . . . . . . . . . . . . 3-14 3-12*

Section VIQuality Control

* Quality Control . . . . . . . . . . . . . . . . . . 3-15 3-12*

Chapter 4Special Features and ConsiderationsSediment Control Structures . . . . . . . . . . 4-1 4-1Air Entrainment . . . . . . . . . . . . . . . . . . . 4-2 4-3Hydraulic Jump in OpenChannels . . . . . . . . . . . . . . . . . . . . . . . 4-3 4-3

Open Channel Junctions . . . . . . . . . . . . . 4-4 4-5Hydraulic Model Studies . . . . . . . . . . . . 4-5 4-8

i

EM 1110-2-1601Change 130 Jun 94

Subject Paragraph Page

* Chapter 5Methods for Predicting n Valuesfor the Manning EquationIntroduction . . . . . . . . . . . . . . . . . . . 5-1 5-1Approach . . . . . . . . . . . . . . . . . . . . . 5-2 5-1Hydraulic Roughness by

Handbook Methods . . . . . . . . . . . . . 5-3 5-1Base n Values (nb) for

Channels . . . . . . . . . . . . . . . . . . . . 5-4 5-1Hydraulic Roughness by

Analytical Methods . . . . . . . . . . . . . 5-5 5-2Composite n Values and

Hydraulic Radius . . . . . . . . . . . . . . . 5-6 5-12Expansion and Contraction

in a 1-D Model . . . . . . . . . . . . . . . . 5-7 5-14Unforeseen Factors . . . . . . . . . . . . . . 5-8 5-14 *

Appendix AReferences

Appendix BPlates

Appendix CNotes on Derivation and Use of HydraulicProperties by the Alpha Method

Subject Paragraph Page

Appendix DComputer Program for Designing Banked Curvesfor Supercritical Flow in Rectangular Channels

Appendix ETheory of Combining Flow at Open ChannelJunctions (Confluences)

Appendix FReport on Standardization of Riprap Gradations

Appendix GVelocity Estimation Based on Field Observations

Appendix HExamples of Stone Size Calculations

Appendix INotation

ii

EM 1110-2-16011 Jul 91

Chapter 1Introduction

1-1. Purpose

This manual presents procedures for the design analysisand criteria of design for improved channels that carryrapid and/or tranquil flows.

1-2. Scope

Procedures are presented without details of the theory ofthe hydraulics involved since these details can be found inany of various hydraulic textbooks and publications avail-able to the design engineer. Theories and procedures indesign, such as flow in curved channels, flow at bridgepiers, flow at confluences, and side drainage inlet struc-tures, that are not covered fully in textbooks are discussedin detail with the aid of Hydraulic Design Criteria (HDC)charts published by the US Army Engineer WaterwaysExperiment Station (USAEWES). The charts and otherillustrations are included in Appendix B to aid the desig-ner. References to HDC are by HDC chart number. Theuse of models to develop and verify design details isdiscussed briefly. Typical calculations are presented toillustrate the principles of design for channels under vari-ous conditions of flow. Electronic computer program-ming techniques are not treated in this manual. However,most of the basic hydraulics presented herein can beadapted for computer use as illustrated in Appendix D.

1-3. References

References are listed in Appendix A.

1-4. Explanation of Terms

Abbreviations used in this manual are explained in theNotation (Appendix I). The symbols employed hereinconform to the American Standard Letter Symbols forHydraulics (American Society of Mechanical Engineers1958) with only minor exceptions.

1-5. Channel Classification

In this manual, flood control channels are consideredunder two broad classifications: rapid- and tranquil-flowchannels. The most important characteristics that apply torapid and tranquil flows are listed below:

a. Velocities. Rapid flows have supercritical

velocities with Froude numbers greater than 1 (F > 1),and tranquil flows have subcritical velocities with Froudenumbers less than 1 (F < 1).

b. Slopes. Invert slopes in general are greater thancritical slopes (So > Sc) for rapid flow and less than criti-cal slopes (So < Sc) for tranquil flow.

c. Channel storage. Channel storage is usuallynegligible in rapid flow, whereas it may be appreciable innatural rivers with tranquil flow.

d. Discharge. All discharges are normally confinedwithin the channel for rapid