Hydraulics Manual
The Hydraulics Manual provides detailed information on hydrologic and hydraulic analysis related to highway design. This manual should be used in conjunction with the WSDOT Highway Runoff Manual and the WSDOT Design Manual, specifically Section 1210.
Individual Chapters
Contents (PDF 184KB)
Chapter 1 Design Policy (PDF 553KB)
Chapter 2 Hydrology (PDF 2.0MB)
Chapter 3 Culvert Design (PDF 9.4MB)
Chapter 4 Channels and Floodplains (PDF 798KB)
Chapter 5 Drainage of Highway Pavements (PDF 693KB)
Chapter 6 Storm Sewer, Drain Pipe, Underdrain Pipe (PDF 573KB)
Chapter 7 Water Crossings (PDF 214KB)
Chapter 8 Pipe Classifications and Materials (PDF 541KB)
Chapter 9 Highway Rest Areas (PDF 13KB)
Chapter 10 Woody Material (PDF 3.7MB)
Glossary and Sources (PDF 347KB)
Revision History
April 2026
April 2025
April 2024
May 2023
April 2022
March 2022
April 2019
March 2017
January 2015
June 2010
January 2010
July 2008
Slow down – lives are on the line.
Drive the posted speeds, they’re there for your safety.
Phone down, eyes up.
Pay attention – both to workers directing you and to surrounding traffic.
Stay calm
Expect delays, leave early or take an alternate route if possible; no appointment is worth risking someone’s life.