Preparing Wetland Reports


Wetland reports are advised, and sometimes required, for development projects where wetlands may be affected. Thorough wetlands reports reduce project delays by providing local governments and regulatory agencies with the information needed to make informed and timely decisions. A typical report includes a wetland assessment, an impact assessment, and a mitigation proposal. This is only a recommended format. More or less detail may be necessary depending on the complexity of the project. Check with your local county or city Planning Department for specific requirements.

Wetland Assessment

The wetland assessment provides detailed information about wetlands on the site. The information required for a complete wetland assessment falls into three categories: wetland community description, delineation report, and an assessment of the functions and values provided by the wetland.

Wetland Community Description

Each wetland community on the site should be described by including:

  • composition of dominant plant species
  • a map showing the distribution of dominant plants
  • U. S. Fish and Wildlife (Cowardin) classification
  • connection and proximity to nearby water bodies
  • known or suspected wildlife use
  • evidence of recent or historic disturbances
  • habitat features; (color photographs are useful in portraying these features)
  • a brief description of adjacent upland plant communities
  • its rating, based on Ecology’s Washington State Wetlands Rating System

Delineation Report

Delineation reports should explain both how and when the delineation was conducted. All delineations conducted for state or local government approval should be done using the Washington State Wetland Identification and Delineation Manual (1997). This manual is consistent with the 1987 Corps Manual, so the same report can be submitted to the Corps. A good delineation report includes:

  • complete set of the field data forms that were filled out during the wetland determination and delineation
  • site map showing wetland boundaries and the locations of all data points
  • topographic map of the area
  • site designation on a National Wetlands Inventory map
  • site designation on local wetland inventories (when available)
  • site designation on a Soils Survey Report soils map
  • any previous site documentation and/or analysis (e.g. environmental checklist, Environmental Impact Statement, or geotechnical report)
  • Washington Natural Heritage Program data on rare plants, or high quality wetlands
  • WA Department of Wildlife Nongame and Priority Habitat information
  • Federal Emergency Management Agency (FEMA) Flood Insurance Rates maps

For large and/or complex projects, a large scale (1”:400’ to 1”:100’) air photo with overlays displaying site property and wetland boundaries is helpful.

Values and Functions Assessment

Wetland functions and values assessments should be conducted by individuals with training or expertise in plant ecology, wildlife biology, and hydrology. Functions and values that should be evaluated include, but are not limited to: water quality improvement, fisheries and wildlife habitat, flood and stream flow attenuation, and recreation and aesthetics.

The report should explain what methods were used to assess the wetland functions, and the strengths and limitations of the methods applied. Another acceptable method for assessing wetland functions and values is for qualified staff to use “best professional judgment”. If best professional judgment is used, it is particularly important to explain what factors or criteria were used to reach any conclusions on functions and values. When detailed habitat information is needed sites may be evaluated using the Habitat Evaluation Procedure (HEP).

Impact Assessment and Brief Project Description

The wetland report should provide detailed information on how wetland functions and values will be adversely affected by the proposed project. The report should discuss the effects of both direct impacts (e.g. filling, dredging, clearing, and alterations to wetland hydrology) as well as indirect impacts (increased intrusion, increased noise, light, and glare, etc.) on each wetland. In addition, specific water quality impacts (e.g. sedimentation, nutrients, hydrocarbons, and toxics) should be discussed. The report should estimate the area (in square feet) of each wetland plant community that will be directly affected by the project. A site plan should be included which clearly identifies all areas of direct and indirect impact.

Mitigation Proposal

The mitigation section of the report should include a discussion on how the project has been designed to avoid and minimize adverse impacts to wetlands. This section should also discuss how wetland buffers and stormwater treatment facilities will be provided. Each of the anticipated impacts noted under the previous section should be addressed here, relative to the effectiveness of the mitigation at replacing lost functions.

If any wetland creation, restoration, or enhancement is proposed as compensation, a plan should be provided. The plan should follow the outline presented in the Guidelines for Developing Freshwater Mitigation Plans and Proposals prepared by the Department of Ecology.

Important Note: The foregoing investigations and reports are usually only required if development actually impacts a wetland or its buffers. Often it is possible to avoid encroaching on these areas when planning for access, utilities, and structures. Avoiding disturbance of wetlands, associated riparian areas, and their buffers is often the most economically and environmentally sound option.

For more information

For more specific information regarding wetlands assessment, evaluations, delineation, and mitigation; please contact your County or City Planning Departments for guidance and requirements.

The Department of Ecology maintains a website ( which provides a wealth of information relating to wetlands functions, values, stewardship, regulatory, and other issues.

This material has been adapted from the WA. State Depart. of Ecology Publication Number 91-104, revised by Greenbelt Consulting, 2005.