Wetland & stream assessment

Use this page to complete wetland and stream assessment. Biologists must meet the minimum qualifications for wetland biologists (pdf 566 kb) to complete wetland and stream assessments on Washington State Department of Transportation (WSDOT) projects. An assessment results in a Wetland and Stream Assessment Report (WSAR). 

Documenting existing conditions of wetlands and other waters helps project engineers and designers avoid and minimize impacts to waters. We use assessments of impacted wetlands and streams to design compensatory mitigation. Locations for future compensation sites also require an assessment to determine the boundary between existing wetland areas and where new wetlands will be established. Wetland and stream assessment informs National Environmental Policy Act (NEPA) documentation and permit applications, including the joint aquatic resource permit application (JARPA).

Follow the steps on this page:

Read Chapter 431: Wetlands in the WSDOT Environmental Manual for policies regarding wetlands. See our NEPA &SEPA Guidance and Environmental permits & approval pages for information on permit applications.

After using this page to locate wetlands and streams in your project, use the Determining jurisdiction of wetlands & other waters page to determine which agency has jurisdiction. See our Wetland mitigation page for mitigation sequencing and early planning considerations.

Request a wetland & stream assessment

The Project Engineer Office (PEO) works with environmental managers and permit coordinators to request a wetland and stream assessment from a WSDOT regional or headquarters environmental office or consultant. The PEO should plan enough lead time for the biologist to conduct field work during the growing season, typically between March and October, depending on your location.

The PEO provides the biologist:

  • Project description, purpose, and location
  • Project plan sheets - showing all areas of potential effect, including temporary impact areas, and potentially impacted ditch sections, with flow direction and known connecting infrastructure such as culverts or stormwater features
  • Written right of entry (ROE) - for access to non-DOT property, if within the project area. Procuring ROE can take significant time. Initiate the process early to help avoid project delays
  • Survey crew – biologist will coordinate survey needs with survey following field work

Use the Generic Scope of Work for Delineation (docx 54 kb) to help build the wetland and stream delineation and assessment section in your consultant contracts.

Determine project documents

The wetland biologist coordinates with the project team to determine the necessary documentation for a given project. A biologist completes wetland and stream assessment tasks and prepares a Wetland and Stream Assessment Report (WSAR).

If needed, use the Wetland Discipline Report (pdf 49 kb) checklist to satisfy NEPA. Wetland Discipline Reports generally document existing conditions, impact analysis, and conceptual mitigation. Avoid duplicating information.

Coordinate with your project team to “right size” your documentation. For example, a Discipline Report may end up as a short document covering project description, summarizing existing conditions and impact analysis, and include the WSAR and conceptual mitigation memo as attachments. See our EA/EIS process and Prepare quality environmental documents pages for more information on NEPA documentation.

If needed, use the Vegetation Discipline Report (pdf 54kb) checklist and the Vegetation Discipline Report (pdf 73 kb) template to aid document development and review.   

Prepare for field work

Prepare for field work by estimating presence of sensitive resources in the project vicinity and gathering background information. Our biologists use the WSDOT GIS Workbench and external partners may access this information from other data sources. Review the following to prepare for field work:

Avoid poisonous and harmful plants when working in the field. See Poisonous plants of Washington State (pdf 7.7 mb) or take the poisonous and harmful plants of Washington State e-learning on the Environmental training page. To print in booklet form, select Poisonous plants of Washington State (pdf 7.6 mb), from print settings select “print on both sides of paper” and “flip on short edge.”

Perform wetland assessment

If you discover archeological materials or human remains during fieldwork, use the Cultural resources and wetlands (pdf 2.2 mb) document to comply with federal and state cultural resource laws and regulations.


Use the Corps of Engineers Wetlands Delineation Manual for delineation methods outlined by the US Army Corps of Engineers (the Corps). The Corps considers wetland delineations valid for five years from the date of field work.

Determine which Land Resource Region (LRR) your project is in using the Major Land Use Resource Areas map (pdf 626 kb). For delineations occurring in LRR A or LRR E, use the Western Mountains, Valleys, and Coast Regional Supplement. For delineation occurring in LRR B, use the Arid West Regional Supplement.

Follow our Sensitive areas naming conventions (pdf 562 kb) guide when identifying wetlands and other waters in the field and on plans and figures.

Use our Road prisms (pdf 212 kb) guidance when projects include wetlands located adjacent to road prisms.

See our Cut slopes (pdf 229 kb) guidance for projects involving wetlands on cut slopes.

Find information about isolated wetlands on our State water quality jurisdiction over wetlands & other waters page.

Use these tools, forms, guidance, and links for collecting vegetation, soil, and hydrology data.

Wetland determination data forms

Use our Wetland Determination Data Forms (ftp server) for both Arid West (AW) and Western Mountains, Valleys, and Coast (WMVC) Regions to record sample point data. The forms require a full Windows operating system and Excel. Mobile versions do not support the macros used in the forms.

Built-in features of the WSDOT forms include tools for inserting scientific plant names with their associated wetland indicator status (WIS), also referred to as “FAC status”, automated calculations, and dropdown menus for common responses.


Reference the most recent version of the Corps National Wetland Plant List on their webpage. Use the Plant Code (pdf 271 kb) list to record field data for plants commonly found in Washington. This list provides scientific and common names, native vs. introduced, and WIS of a subset of commonly encountered plants. 

A corresponding WSDOT auto-text macro for Microsoft Word inserts information when you enter plant codes, including scientific name, common name, and WIS. Find installation instructions, plant codes, and the macro file “Autotext_Plants.dotm” on the WSDOT public FTP server.


Reference the most recent versions of the U.S. Department of Agriculture (USDA) National Resource Conservation Service (NRCS) publications to describe soils on your project site:


Use the following tools to support the collection and analysis of hydrologic characteristics of your site.

Rating forms

Before rating your wetland, use the boundary between Eastern and Western Washington (pdf 59 kb) map to determine the geographic area of your project. Determine the appropriate Washington State Department of Ecology’s (Ecology) Washington State Wetland Rating System for your region.

Use the following forms to rate wetlands in your study area.

Western Washington forms:

Eastern Washington forms:

Classification methods

We use two different classification methods for wetland assessment.

Use the Classification of Wetlands and Deepwater Habitats of the United States (pdf 6.3 mb), also referred to as Cowardin, to classify wetland vegetation.

Use Hydrogeomorphic Wetland Classification System (pdf 3.2 mb) to classify landscape position and water movement in wetlands and document wetland ratings.

Functions assessment

Potentially impacted wetlands require a functions assessment.

Use the Wetland Functions Characterization Tool for Linear Projects (pdf 96 kb) referred to as the Best Professional Judgement (BPJ) tool, to perform a functions assessment. A nationally or state recognized rapid functional assessment method isn’t available. WSDOT, along with regulatory and resource agencies and one tribe, developed BPJ to characterize wetland functions for WSDOT projects. This tool evaluates and documents functions of potentially impacted wetlands on your project, including water quality, hydrologic, biological, and social functions.

Use Ecology’s Credit/Debit method for in-lieu fee mitigation proposals on projects with minimal wetlands. It calculates if a proposed wetland mitigation project adequately replaces lost functions and values of impacted wetlands. Applying the Credit/Debit method to projects with more than a few wetlands is challenging, so the BPJ tool is preferable for most WSDOT projects.

Perform stream & tidal water assessment

During the environmental review and permitting phase of a project, identify streams and tidal waters within a project’s area of potential effect. Gather the following information and document it in the WSAR.

Ordinary High Water Mark (OHWM) delineation methods

For non-tidal streams and other waters, follow the Corp’s methodology for OHWM delineation in non-tidal areas established in the Corps regulatory guidance letter 05-05. In addition, use the following region specific resources:

Follow our Sensitive areas naming conventions (pdf 126 kb) when identifying rivers and streams in the field and on plans and figures.

High Tide Line (HTL) delineation

For tidal water, review the Corp’s Electronic Permit Guide Book – Streams, Rivers, and Tidal Waters and gather HTL information including:

  • Background data – find relevant tidal information such as
  • Field observations –  
    • When possible, determine where the listed elevations for HPT and MHHW occur on your site.
    • Identify physical indicators of the high tide line such as lines of vegetation, fine shell, debris, oil, or scum.     
  • Photos – clearly show the physical indicators of HTL observed at your site.

Prepare a rationale describing how you placed the HTL and include it in your WSAR.

If you need help delineating the HTL contact the liaison program at ESOPermittingliaisons@wsdot.wa.gov .

Follow our Sensitive areas naming conventions (pdf 126 kb) when identifying the high tide line in the field and on plans and figures.

Evaluate wetland & stream buffers

Local agencies and many tribes require regulatory buffers for wetlands, streams, and other waters. Review wetland and stream regulations in local municipal codes or critical areas ordinances to determine regulatory buffer requirements for your project. See the Municipal Research and Services Center website to look up city or county  codes. Check for applicable buffer information for other aquatic resources such as lakes or tidal waters. 

Apply the most conservative or widest applicable buffer, when given a range of buffer widths to interpret. Permitting agencies consider transportation projects, including fish passage projects, as high intensity land use, major new development, or other similar land use designations. They require application of the most protective or widest buffers.

Though local area permitting usually exempts standalone fish passage projects, we still apply regulatory buffers. For information on fish passage exemptions from local agency permitting, see our Local permits and approvals page.

Some projects may span several jurisdictions including cities, counties, and tribal lands. Apply buffer widths of the jurisdiction each wetland falls within.

See our Buffers across roadways (pdf 227 kb) guidance to learn more about wetland buffers adjacent to or extending across roadways.

Perform ditch assessment

If a project proposes impacts to ditches, the PEO requests that a biologist assess potentially impacted ditch sections for jurisdictional features. Ideally, ditch assessments occur during the wetland assessment field work. If you don’t know which ditch sections the project might impact at the time of the wetland assessment work, assess ditches at a later time and prepare a separate jurisdictional ditch memo.

The PEO provides the biologist with plan sheets identifying potentially impacted ditch sections, known flow directions, and relevant infrastructure such as culverts and stormwater features. We don’t make jurisdictional calls, but can recommend a jurisdictional determination. The Corps makes the final decision. See our US Army Corps of Engineers jurisdiction over wetlands and other waters page for more information.

Identify and document jurisdictional ditches

Use the latest Rule defining Water of the United States (WOTUS) on the EPA website to understand which ditches are jurisdictional. Only assess ditch sections that the project might impact to make a jurisdictional recommendation(s).

Assess ditches by walking ditch lines up gradient from the nearest downstream WOTUS. When you cannot physically access the area, use background information such as topographic maps and the USGS StreamStats web mapper. Use aerial photos to help identify where the ditch flows and if it drains to a WOTUS.

When available, review as-built plan sheets and design information from previous projects to understand location of drainage features and their intended function.

Use the our jurisdictional ditch recommendation field form (doc 18 kb) during field work to document ditch sections with proposed impacts. Survey all ditch centerlines. Include jurisdictional and non-jurisdictional ditch centerlines on plan sheets, along with flow direction as shown in our MicroStation application drawing patterns (pdf 1.65 mb). You don’t need to flag jurisdictional ditch features unless they contain wetlands or streams.


  • Ditches regulated as wetlands in the wetland section of the WSAR.
  • Ditches regulated as tributaries in the stream section of the WSAR.
  • Jurisdictional ditches in the ditch section of the WSAR - if you can identify ditch sections that the project may impact at the time of the wetland and stream assessment field work. If you don’t know which ditch sections will be impacted, prepare a jurisdictional ditch memo when the information becomes available and field work is complete.
  • Ditches exempted form Corps jurisdiction - on the field data form. Save it in the project file as internal documentation showing you evaluated the ditch and recommended as a ditch exempt from Corps jurisdiction.

Coordinate with survey & design

Following field work, coordinate with your region’s survey crew. Provide them a sketch map of all identified features. Coordinate with your PEO to develop and finalize plan sheets showing all identified waters and their buffers. For projects with tidal water delineations, include HTL and MHW lines on the plan sheets.

Prepare a Wetland & Stream Assessment Report

Use the Wetland and Stream Assessment Report (doc 118 kb) template and review these report examples to document your wetland and stream assessment:

Our WSARs follow the Corps Components of a Complete Wetland Delineation Report (pdf 1.5 mb) guidance. Reports are valid for five years from the date of the field work. If the project is delayed, review field work and update