Hydraulics Manual

Publication Number
M 23-03
Publication Version
M 23-03.10
Manual Manager
Julie Heilman
Design Office, Engineering and Regional Operations Division

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 Open Channel Flow (PDF 798KB)
Chapter 5 Drainage of Highway Pavements (PDF 693KB)
Chapter 6 Storm Sewer (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 in the Riparian Zone (PDF 3.7MB)

Glossary and Sources (PDF 347KB)

Revision History

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. 

In 2023, speeding continued to be a top reason for work zone crashes.

Even one life lost is too many.

Fatal work zone crashes doubled in 2023 - Washington had 10 fatal work zone crashes on state roads.

It's in EVERYONE’S best interest.

95% of people hurt in work zones are drivers, their passengers or passing pedestrians, not just our road crews.