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Hydraulic Engineering Circular No. 23 v2

Publication No. FHWA NHI HEC-23
September 2009
U.S. Department of Transportation
Bridge Scour and Stream Instability Countermeasures
Experience, Selection, and Design Guidance
Third Edition

Federal Highway Administration

Technical Report Documentation Page

1. Report No. FHWA NHI
                    HEC-23
2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle

BRIDGE SCOUR AND STREAM INSTABILITY
COUNTERMEASURES
Experience, Selection and Design Guidance
Volumes 1 and 2
Third Edition
5. Report Date

September 2009
6. Performing Organization Code
7. Author(s)

P.F. Lagasse, P.E. Clopper, J.E. Pagán-Ortiz, L.W. Zevenbergen,
L.A. Arneson, J.D. Schall, L.G. Girard
8. Performing Organization Report No.
9. Performing Organization Name and Address

Ayres Associates
3665 JFK Parkway
Building 2, Suite 200
Fort Collins, Colorado 80525
10. Work Unit No. (TRAIS)
11. Contract or Grant No.

DTFH61-06-D-00010/T-06-001
12. Sponsoring Agency Name and Address

Office of Bridge Technology
FHWA, HIBT-20
1200 New Jersey Ave.,
Washington, D.C. 20590
        National Highway Institute
4600 North Fairfax Dr.,
Suite 800 SE
Arlington, Virginia 22203
13. Type of Report and Period Covered
14. Sponsoring Agency Code
15. Supplementary Notes

Project Managers: Dr. Larry A. Arneson and Mr. Jorge E. Pagán-Ortiz, FHWA
Technical Assistants: Scott Anderson, Kornel Kerenyi, Joe Krolak, Barry Siel, FHWA; S. Mishra, Ayres Associates;
B. Hunt, STV Inc.
16. This document identifies and provides design guidelines for bridge scour and stream instability countermeasures that have been implemented by various State departments of transportation (DOTs) in the United States. Countermeasure experience, selection, and design guidance are consolidated from other FHWA publications in this document to support a comprehensive analysis of scour and stream instability problems and provide a range of solutions to those problems. Selected innovative countermeasure concepts and guidance derived from practice outside the United States are introduced. Management strategies and guidance for developing a Plan of Action for scour critical bridges are outlined, and guidance is provided for scour monitoring using portable and fixed instrumentation.

The results of recently completed National Cooperative Highway Research Program (NCHRP) projects are incorporated in the design guidance, including: countermeasures to protect bridge piers and abutments from scour; riprap design criteria, specifications, and quality control; and environmentally sensitive channel and bank protection measures. This additional material required expanding HEC-23 to two volumes. Volume 1 now contains a complete chapter on riprap design, specifications, and quality control as well as an expanded chapter on biotechnical countermeasures. The guidance on scour monitoring instrumentation has been updated and now includes additional installation case studies. Volume 2 contains 19 detailed design guidelines grouped into six categories, including countermeasures for: (1) stream instability (2) streambank and roadway embankment protection, (3) bridge pier protection, (4) abutment protection, (5) filter design, and (6) special applications.
17. Key Words

stream stability, scour, countermeasures, plan of action, bendway weirs, soil cement, wire enclosed riprap, articulating concrete block systems, concrete armor units, gabion mattresses, grout filled mattresses, grout bags, rock riprap, partially grouted riprap, spurs, guide banks, check dams, revetments, scour monitoring instrumentation
18. Distribution Statement

This document is available to the public through the National Technical Information Service, Springfield, VA 22161 (703) 487-4650
19. Security Classif. (of this report)

Unclassified
20. Security Classif. (of this page)

Unclassified
21. No. of Pages

376
22. Price

Form DOT F 1700.7 (8-72)                                                                                Reproduction of completed page authorized

ACKNOWLEDGMENTS

This manual is a major revision of the second edition of HEC-23 which was published in 2001. The writers wish to acknowledge the contributions made by Morgan S. Byars (formerly Ayres Associates) as a co-author of the first edition (1997). Technical assistance for the second edition was provided by J. Sterling Jones (FHWA) and A. Firenzi, J.L. Morris, E.V. Richardson, W.J. Spitz, and A. Waddoups (Ayres Associates).

TABLE OF CONTENTS

Volume 1

Volume 2

DESIGN GUIDELINES

SECTION 1 - COUNTERMEASURES FOR STREAM INSTABILITY
SECTION 2 - COUNTERMEASURES FOR STREAMBANK AND ROADWAY EMBANKMENT PROTECTION
SECTION 3 - COUNTERMEASURES FOR BRIDGE PIER PROTECTION
SECTION 4 - COUNTERMEASURES FOR ABUTMENT PROTECTION
SECTION 5 - FILTER DESIGN
SECTION 6 - SPECIAL APPLICATIONS

DISCLAIMER

Mention of a manufacturer, registered or trade name does not constitute a guarantee or warranty of the product by the U.S. Department of Transportation or the Federal Highway Administration and does not imply their approval and/or endorsement to the exclusion of other products and/or manufacturers that may also be suitable.

VOLUME 2
COUNTERMEASURE DESIGN GUIDELINES

INTRODUCTION

In this volume design guidelines are provided for a variety of stream instability and bridge scour countermeasures. Most of these countermeasures have been applied successfully on a state or regional basis, but, in several cases, only limited design references are available in published handbooks, manuals, or reports. No attempt has been made to include in this document design guidelines for all the countermeasures listed or referenced in Volume 1.

Countermeasure design guidelines formerly presented in HEC-20 (spurs, guide banks, drop structures) and in HEC-18 (riprap at abutments and piers) are now consolidated in this document. Since many bridge scour and stream instability countermeasures require riprap revetment as an integral component of the countermeasure, riprap revetment design guidance is summarized in Design Guideline 4. An appropriate granular or geotextile filter is essential for any countermeasure requiring a protective armor layer (e.g., riprap, articulating concrete blocks, etc.). Filter design guidance is provided in Design Guideline 16.

Design Guideline 8 - Articulating Concrete Block Systems, Design Guideline 9 - Grout-Filled Mattresses, and Design Guideline 10 - Gabion Mattresses each contain two countermeasure applications: (1) bankline revetment or bed armor, and (2) pier scour protection. Consequently, these three design guidelines appear in Section 2, but are referenced in Section 3 with a page citation to the pier protection application.

A number of highway agencies provided specifications, procedures, or design guidelines for bridge scour and stream instability countermeasures that have been used successfully locally, but for which only limited design guidance is available outside the agency. Several of these are presented as design guidelines for the consideration of and possible adaptation to the needs of other highway agencies (see for example, Design Guideline 6, Wire Enclosed Riprap Mattress, and Design Guideline 13, Grout/Cement Filled Bags). These specifications, procedures, or guidelines have not been evaluated, tested, or endorsed by the authors of this document or by the FHWA. They are presented here in the interests of information transfer on countermeasures that may have application in another state or region.

Since publication of the Second Edition of HEC-23 in 2001, both the Transportation Research Board through the NCHRP Program and FHWA have sponsored a number of research projects to improve the state of practice in bridge scour and stream instability countermeasure technology and provide definitive guidance to bridge owners in countermeasure design. Among the projects that represent advances in countermeasure technology that have been incorporated into the Design Guidelines are:

  • NCHRP Report 544 -Environmentally Sensitive Channel and Bank Protection Measures
  • NCHRP Report 568 -Riprap Design Criteria, Specifications, and Quality Control
  • NCHRP Report 587 -Countermeasures to Protect Bridge Abutments from Scour
  • NCHRP Report 593 -Countermeasures to Protect Bridge Piers from Scour

DESIGN GUIDELINES

The following specifications, procedures, or design guidelines are included in this volume. The application of the countermeasure and the contributing source(s) of information are also indicated below.

SECTION 1 - COUNTERMEASURES FOR STREAM INSTABILITY

Design Guideline 1
  • Bendway Weirs/Stream Barbs
    • Source(s): Colorado Department of Transportation
      Washington State Department of Transportation
      Tennessee Department of Transportation
      Soil Conservation Service (now Natural Resources Conservation Service
      U.S. Army Corps of Engineers
    • Application: Bankline protection and flow alignment in meandering channel bends
Design Guideline 2
  • Spurs
    • Source(s): HEC-20 Stream Stability at Highway Structures (Second Edition)
      NCHRP Report 568
    • Application: Bankline stabilization and flow alignment
Design Guideline 3
  • Check Dams/Drop Structures
    • Source(s): HEC-20 Stream Stability at Highway Structures (Second Edition)
      HEC-14 Hydraulic Design of Energy Dissipators for Culverts and Channels
    • Application: Correcting or preventing channel degradation

SECTION 2 - COUNTERMEASURES FOR STREAMBANK AND ROADWAY EMBANKMENT PROTECTION

Design Guideline 4
  • Riprap Revetment
    • Source(s): NCHRP Report 568
    • Application: Bankline/abutment protection and riprap component of many other countermeasures
Design Guideline 5
  • Riprap Design for Embankment Overtopping
    • Source(s): NCHRP Report 568
    • Application: Protection for roadway approach embankments and flow control countermeasures
Design Guideline 6
  • Wire Enclosed Riprap Mattress
    • Source(s): New Mexico State Highway and Transportation Department
    • Application: Revetment for banklines, guide banks, and sloping abutments
Design Guideline 7
  • Soil Cement
    • Source(s): Portland Cement Association
      Pima County Arizona
      Maricopa County Arizona
    • Application: Revetment for banklines and sloping abutments, drop structures, and bed armor
Design Guideline 8
  • Articulating Concrete Block Systems for Bank Protection or Bed Armor
    • Source(s): Harris County Flood Control District (2001)
      Federal Highway Administration
      Maine Department of Transportation
      Minnesota Department of Transportation
    • Application 1: Bankline revetment and bed armor
Design Guideline 9
  • Grout-Filled Mattresses for Bank Protection or Bed Armor
    • Source(s): Federal Highway Administration
      Oregon Department of Transportation
      Arizona Department of Transportation
    • Application 1: Bankline revetment and bed armor
Design Guideline 10
  • Gabion Mattresses for Bank Protection or Bed Armor
    • Source(s): Federal Highway Administration
    • Application 1: Bankline revetment and bed armor

SECTION 3 - COUNTERMEASURES FOR BRIDGE PIER PROTECTION

Design Guideline 8
  • Articulating Concrete Block Systems at Bridge Piers
    • Source(s): NCHRP Report 593
    • Application 2: Pier scour protection
Design Guideline 9
  • Grout-Filled Mattresses at Bridge Piers
    • Source(s): NCHRP Report 593
    • Application 2: Pier scour protection
Design Guideline 10
  • Gabion Mattresses at Bridge Piers
    • Source(s): NCHRP Report 593
    • Application 2: Pier scour protection
Design Guideline 11
  • Rock Riprap at Bridge Piers
    • Source(s): HEC-18 Scour at Bridges (Third Edition)
      NCHRP Report 593
      NCHRP Report 568
    • Application: Pier scour protection
Design Guideline 12
  • Partially Grouted Riprap at Bridge Piers
    • Source(s): NCHRP Report 593
    • Application: Pier Scour Protection

SECTION 4 - COUNTERMEASURES FOR ABUTMENT PROTECTION

Design Guideline 13
  • Grout/Cement Filled Bags
    • Source(s): Maryland State Highway Administration
      Maine Department of Transportation
    • Application: Protection of undermined areas at piers and abutments, and bed armor
Design Guideline 14
  • Rock Riprap at Bridge Abutments
    • Source(s): NCHRP Report 568
      NCHRP Report 587
    • Application: Abutment scour protection
Design Guideline 15
  • Guide Banks
    • Source(s): HEC-20 Stream Stability at Highway Structures (Second Edition)
      NCHRP Report 568
    • Application Abutment scour protection

SECTION 5 - FILTER DESIGN

Design Guideline 16
  • Filter Design
    • Source(s): NCHRP Report 568
      NCHRP Report 593
    • Application: Filter for revetment or countermeasure armor

SECTION 6 - SPECIAL APPLICATIONS

Design Guideline 17
  • Riprap Design for Wave Attack
    • Source(s): HEC-25 (1st and 2nd Editions)
    • Application: Protection for coastal roadway embankments
Design Guideline 18
  • Riprap Protection for Bottomless Culverts
    • Source(s): FHWA Reports FHWA-RD-02-078 and FHWA-HRT-07-026
    • Application: Scour protection at bottomless culverts
Design Guideline 19
  • Concrete Armor Units (Toskanes and A-Jacks®)
    • Source(s): Testing at Colorado State University
    • Application: Pier scour protection
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Updated: 09/20/2011

FHWA
United States Department of Transportation - Federal Highway Administration