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Hydraulics & hydrology

Find technical support, training and policy in the fields of hydraulics, fish passage, hydrology and stormwater to ensure our roadways provide a safe, effective and efficient movement of people and goods while maintaining the natural movement and treatment of water throughout our watersheds and water bodies.

Bridge Design Manual LRFD, M 23-50 provides guidance to WSDOT bridge design engineers on the design criteria, analysis methods, and detailing procedures for the preparation of highway bridge and structure construction plans, specifications, and estimates.

Construction Manual, M 41-01 provides department construction engineering personnel instruction for fulfilling the objectives, procedures, and methods for construction administration of Washington State transportation projects.

Design-Build Manual, M 3126 provides detailed guidance to WSDOT staff on policies, processes, and procedures specific to design-build and to support consistent and cost-effective design-build project delivery.

Design Manual, M 22-01 provides policies, procedures, and methods for developing and documenting the design of improvements to the transportation network in Washington. It has been developed for state facilities and may not be appropriate for all county roads or city streets that are not state highways.

Design Manual, M 22-01, Chapter 800 Hydraulic Design (PDF 329KB) is intended to serve as a guide to highway designers so they can identify and consider hydraulic-related factors that impact the design.

Electronic Engineering Data Standards Manual, M 3028 defines standards and procedures for preparing, delivering, and archiving electronic engineering data created for WSDOT during survey, design, and PS&E phases of highway projects. These standards apply to projects delivered by department staff and consulting firms unless otherwise approved by the WSDOT Project Development Engineer.

Environmental Manual, M 31-11 is a compilation of environmental policies and processes that is to be used as a guidance resource for WSDOT and its environmental consultants. It outlines WSDOT’s legal requirements related to environmental, cultural, historic, and social resources and is a keystone of WSDOT’s environmental compliance strategy.

Geotechnical Design Manual, M 46-03 focuses on geotechnical design, construction, and maintenance to ensure that the soil or rock beneath the ground surface can support the loads and conditions placed on it by transportation facilities.

Highway Runoff Manual, M 31-16 (HRM) provides guidance to direct the planning and design of stormwater management facilities for existing and new Washington State highways, rest areas, park-and-ride lots, ferry terminals, and highway maintenance facilities throughout the state. The HRM establishes minimum requirements and provides uniform technical guidance.

Hydraulics Manual, M 23-03 provides policy for designing hydraulic features related to Washington State Department of Transportation (WSDOT) roadways including hydrology, culverts, open-channel flow, drainage collection and conveyance systems, water crossings, and pipe materials. These hydraulic features maintain safe driving conditions and protect the roadway from surface and subsurface water.

When a project needs a design deviation from the requirements in the WSDOT Hydraulics Manual, the Hydraulics Manual Deviation template (DOCX 49KB) should be used. It requires the approval of both the Region Hydraulics Engineer and the State Hydraulic Engineer.

Local Agency Guidelines (LAG), M 36-63 provides local agencies with statewide policies and standards to follow when using Federal Highway Administration (FHWA) funds for transportation projects.

Maintenance Manual, M 51-01 provides uniform operating procedures and performance guidelines for maintaining the highway system in Washington State.

Plans Preparation Manual, M 22-31 provides instructions and guidance for the preparation of right of way plans, contract plans, special provisions, and estimate packages for highway construction projects. It also provides the standards used in the preparation of these plans using Computer Aided Drafting and Design (CADD).

Roadside Manual, M 25-30 supplements the Roadside Policy Manual (RPM) by explaining how to implement the policies found in the RPM. Manual describes laws and policies, visual functions, wetlands, wildlife, safety rest areas, soil amendments, contour grading, soil bioengineering, vegetation, restoration, and design enhancement.

Roadside Policy Manual, M 3110 provides practical roadside restoration policies and guidance, which are based on minimizing life cycle costs while providing operational and environmental functions. It promotes ecological context, environmental preservation, and maintainability.

Temporary Erosion and Sediment Control Manual, M 3109 replaces Chapter 6 and Appendix 6A of the WSDOT Highway Runoff Manual. It outlines WSDOT’s policies for meeting the National Pollutant Discharge Elimination System (NPDES) Construction Stormwater General Permit requirements and the requirements in Volume II of the stormwater management manuals published by the Washington State Department of Ecology.

Utilities Manual, M 22-87 provides guidance in accommodating utilities within state right of way in a manner that does not interfere with the free and safe flow of traffic or impair the highway's visual quality. Information is provided about the preparation of utility agreements and utility service agreements.

Getting a printed copy

While there are no plans to distribute printed copies, WSDOT Printing Services offers printing, digitization and duplicating services for state and local agencies, consultants and contractors working with the department.

However, users referencing printed copies should continually consult the online versions on All Manuals & Standards website for post publication updates to ensure they are using the most current design guidance.

Additional design guidance and resources

The resources listed here are intended to be used in conjunction with the WSDOT Hydraulics Manual and WSDOT Highway Runoff Manual.

Bank Stabilization with Fabric Encapsulated Soil Lifts (FESL) (PDF 3.3MB), Billingsley, Zack, 2021, Master’s Thesis, Colorado State University. Most comprehensive guide to date on this technique.

Computational Design Tool for Evaluating the Stability of Large Wood Structures (PDF 132KB) is the technote for design and restoration practitioners to be used when specifying the type of large wood structure and have an assurance that the constructed structure will likely remain in place under the expected conditions.

Environmental Guidance - Stormwater & Water Quality describes procedures to follow to comply with stormwater and water quality regulations including:

  • Clean Water Act, Section 402 - National Pollutant Discharge Elimination System (NPDES) Permits.
  • Water resources & erosion control research & reports.
  • Water resources policies and procedures.

Fish Passage is the source to learn how to reconnect streams under state highways to improve fish passage around the state.

Fox and Bolton (PDF 658KB) is a regional and geomorphic reference for quantities and volumes of instream wood in unmanaged forested basins of Washington State.

Guidance for Flood Risk Analysis and Mapping Document No. 79 (PDF 4.3MB) provides guidance to support the requirements and recommends approaches for effective and efficient implementation of floodway analysis and all the components that accompany it.

Guidance for Flood Risk Analysis and Mapping Document No. 106 (PDF 184KB) explains how the Department of Homeland Security, Federal Emergency Management Agency (FEMA) implements the review and processing of requests to revise Flood Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) reports (collectively referred to as MT-2 requests).

Integrated Streambank Protection Guidelines is based on a set of guiding principles developed by professional resource managers, engineers and other practitioners that was created by a consortium of public agencies to assist property owners, planners, designers and regulators to protect and restore marine, freshwater and riparian fish and wildlife habitat. The agencies involved in developing this series include the Washington Department of Fish and Wildlife, the Washington State Department of Transportation, the Washington Department of Ecology, the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service.

Marine Shoreline Design Guidelines were developed to provide a comprehensive framework for site assessment and alternatives analysis to determine the need for shore protection and identify the technique that best suits the conditions at a given site. These guidelines reflect the variety of conditions found in Puget Sound and were created to inform responsible management of Puget Sound shores for the benefit of landowners and our shared natural resources.

Publications - Hydraulics - Bridges & Structures website provides links to various publications for hydrology, culvert and bridge hydraulics, drainage, and scour.

Stormwater Management Manuals for Western Washington and for Eastern Washington provide stormwater permit implementation and management guidance.

Stream Habitat Restoration Guidelines (PDF 29MB) is a guidance document that was developed by the Aquatic Habitat Guidelines (AHG) Program. AHG is a joint effort among state resource management agencies in Washington, including the Washington Departments of Fish and Wildlife, Ecology, Transportation, Natural Resources, the Recreation and Conservation Office, and the Puget Sound Partnership.

Stream Simulation: An Ecological Approach to Providing Passage for Aquatic Organisms at Road-Stream Crossings Manual (PDF 977KB) contains the information that has been developed for the guidance of employees of the U.S. Department of Agriculture (USDA) Forest Service, its contractors, and cooperating Federal and State agencies.

Water Crossing Design Guidelines were written to help the crossing owner and designer comply with Washington State law that protects fish life. This document covers the design of culverts with new chapters on bridge design, tidally influenced crossings, temporary crossings, culvert abandonment, and project development. It provides practical, real-world knowledge and techniques to improve the overall success of water crossings.

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