HEC-25 3Rd Ed
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Publication No. FHWA-HIF-19-059 January 2020 Hydraulic Engineering Circular No. 25 Highways in the Coastal Environment Third Edition Page Intentionally Left Blank Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA HIF-19-059 4. Title and Subtitle 5. Report Date HIGHWAYS IN THE COASTAL ENVIRONMENT January 2020 Hydraulic Engineering Circular Number 25 6. Performing Organization Code Third Edition 7. Author(s) 8. Performing Organization Report No. Scott L. Douglass and Bret M. Webb 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) South Coast Engineers PO Box 72 Fairhope, AL 36533 11. Contract or Grant No. DTFH61-16-D-00033 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Office of Bridges and Structures Technical Report Federal Highway Administration November 2017-December 2019 1200 New Jersey Avenue, S.E. 14. Sponsoring Agency Code Washington, D.C. 20590 15. Supplementary Notes Project Manager: Brian Beucler, FHWA Office of Bridges and Structures Technical Reviewers: Joe Krolak, Tina Hodges, Rob Kafalenos, Kornel Kerenyi, Rob Hyman, Paul Sharp, Eric Brown, Jia-Dzan (Jerry) Shen, Stephanie Smallegan, Thomas (Beau) Buhring Technical Editor: Valarie Arms 16. Abstract This manual presents tools for the planning, design, and operation of highways in the coastal environment. It focuses on roads near the coast that are influenced by coastal tides and waves constantly, or occasionally during storms. FHWA estimates that there are more than 60,000 miles of these “coastal highways” in the US. A primary goal is the integration of coastal engineering principles and practices in the planning and design of these roads and bridges to make them more resilient. The manual summarizes coastal science concepts and modeling tools that have been developed by the coastal engineering community, and are applicable to highways. This includes engineering tools for estimating water levels, waves, and sand movement. Coastal highway applications include coastal revetment design; planning and alternatives for highways that are threatened by coastal erosion, including nature-based solutions; roads that overwash in storms; roads that are experiencing increased flooding due to sea level rise; coastal bridge issues including wave loads on bridge decks; and coastal scour. The manual presents technical information and methods for assessing the vulnerability of coastal transportation facilities to extreme events with techniques to improve resilience. Some coastal transportation infrastructure is highly exposed to extreme events and that exposure will increase as sea levels rise. Many of the adaptations needed for future sea levels are the same engineering approaches needed for improving infrastructure resilience today. 17. Key Words 18. Distribution Statement Coast, Coastal Engineering, Highways, Hydraulics, Hydrodynamics, Unlimited distribution Tides, Water Levels, Waves, Storm Surge, Erosion, Extreme Events, Sea Level Rise, Shorelines, Protection, Modeling, Nature Based & Natural Infrastructure, Scour, Resilience 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified 434 N/A Form DOT F 1700.7 (8-72) Reproduction of completed page authorized Page Intentionally Left Blank HEC-25 3rd ed. Table of Contents Table of Contents Table of Contents ........................................................................................................................... i List of Figures .............................................................................................................................. ix List of Tables ............................................................................................................................... xx List of Symbols ........................................................................................................................... xxi Acknowledgements ...................................................................................................................x xiv Notice ........................................................................................................................................xxi v Non-Binding Contents ...............................................................................................................xxi v Quality Assurance Statement ................................................................................................... xxv Supporting Purpose .................................................................................................................. xxv Glossary ....................................................................................................................................xx vi List of Acronyms ........................................................................................................................x liv Part 1 – Background & Context .................................................................................................... 1 Chapter 1 - Introduction ................................................................................................................ 3 1.1 Purpose and Scope ..................................................................................................... 3 1.2 Organization ................................................................................................................ 4 1.3 Target Audience .......................................................................................................... 6 1.4 Units in this Manual ..................................................................................................... 6 Chapter 2 - Federal Policy for Coastal Highways ......................................................................... 7 2.1 Federal Highway and the Coast: National Overview ................................................... 7 2.2 FHWA Statutes & Regulations .................................................................................... 7 2.2.1 FHWA Statute .................................................................................................. 7 2.2.2 Appropriation Language .................................................................................. 9 2.2.3 FHWA Regulations .......................................................................................... 9 2.3 Other Federal Agency Coastal Statutes & Regulations ............................................ 11 2.3.1 Rivers and Harbors Act of 1899 [33 U.S.C. § 401 and § 403] ....................... 11 2.3.2 General Bridge Act of 1946 [33 U.S.C. § 525 through 533] .......................... 11 2.3.3 Transportation Act of 1966 [Public Law 89-670] ............................................ 11 2.3.4 Coastal Zone Management Act [16 U.S.C. § 1451-1466] ............................. 12 2.3.5 National Environmental Policy Act [42 U.S.C. § 4321, et seq.] ..................... 12 2.3.6 Clean Water Act [33 U.S.C. § 1251-1387] ..................................................... 12 2.3.7 Endangered Species Act [16 U.S.C. § 1531-1544] ....................................... 13 2.3.8 Coastal Barrier Resources Act [16 U.S.C. § 3501 through 3510] ................. 13 i Table of Contents HEC-25 3rd ed. 2.3.9 Magnuson-Stevens Fishery Conservation and Management Act [16 U.S.C. § 1801-1891d] .................................................................................................. 13 2.3.10 Marine Mammal Protection Act [16 USC §§ 1361-1407] ............................... 13 2.3.11 Migratory Bird Treaty Act [16 U.S.C. §§ 703-712.]. ....................................... 14 2.3.12 National Historic Preservation Act [54 U.S.C. 300101 et seq.] ...................... 14 2.3.13 National Flood Insurance Act of 1968 [42 U.S.C. § 4001 et seq.] ................. 14 Chapter 3 - Coastal Highways: An Overview .............................................................................. 17 3.1 What are Coastal Highways? .................................................................................... 17 3.2 The Extent of Coastal Roads and Bridges ................................................................ 18 3.3 Societal Demand for Coastal Highways .................................................................... 18 3.4 Natural Processes Impacting Coastal Highways ....................................................... 19 3.4.1 Water Level Change ...................................................................................... 19 3.4.2 Sea Level Rise .............................................................................................. 19 3.4.3 Storm Surge .................................................................................................. 19 3.4.4 Major Weather Events ................................................................................... 19 3.4.5 Waves ............................................................................................................ 22 3.4.6 Shoreline Erosion and Barrier Island Breaches ............................................. 22 3.4.7 Littoral Drift .................................................................................................... 22 3.4.8 Shoreline Recession ...................................................................................... 23 3.4.9 Tsunamis ....................................................................................................... 23 3.4.10 Upland Runoff ...............................................................................................