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Wetland Monitoring and Assessment


Over the past century wetlands have been drained, filled, and otherwise impacted so that conserving and restoring remaining wetlands is a priority in many areas. Wetlands provide:

  • Crucial habitat for several fish, wildlife, and plant species.
  • Key ecological functions, including storm water retention and nutrient capture.
  • Ecosystem services such as improved water quality and reduced flooding.

Oregon has explored how to provide credits for restoring and/or maintaining ecosystem services to landowners. It is critical to develop a clearer understanding of the current status and condition of wetlands in order to continue addressing wetland restoration and mitigation actions.

Since 1997, OWEB has provided more than $18 million to wetland restoration projects throughout Oregon. The Department of State Lands (DSL) ensures that wetlands across Oregon, which may be impacted by permitted activities, are replaced by required wetland mitigation actions and that permit conditions are closely followed. However there is no comprehensive program for monitoring and assessing the condition and function of restored, enhanced, or mitigated wetlands in Oregon.

In 2009, OWEB partnered with The Xerces Society for Invertebrate Conservation, Adamus Resource Assessment Inc, and DSL to begin working towards developing and refining monitoring tools such as a preliminary invertebrate index of biological integrity (I-IBI), rapid monitoring techniques, and detailed effectiveness monitoring. The main objectives of the pilot study were to:

  • Increase wetland acreage and gains in wetland function and/or condition by improving pre-implementation evaluation of wetlands
  • Increase the effectiveness of wetland restoration projects by applying past project performance during the development of new projects
  • Increase use and standardization of biological monitoring tools to assess wetland function and condition
  • Provide additional data and information on wetland investments in a widely accessible format and improve accuracy and completeness of such data

Using information obtained from OWEB’s restoration database and DSL’s mitigation database, 50 wetlands in the Willamette Valley were sampled in the summers of 2009 and 2010. Sampling parameters consisted of macroinvertebrates, water quality, wetland soil, wetland vegetation, and observations of birds and amphibians. In addition, a rapid assessment protocol was tested for its reliability in this pilot project.​

Data analysis from various levels of monitoring indicated:

  • Macroinvertebrate sampling and rapid site disturbance assessment are reliable, repeatable, and appear to be consistent between sampling years and sampling teams
  • The macroinvertebrate community in flats wetlands has lower species diversity compared to riverine wetlands. The flats wetlands species are more tolerant of a range of ecological impairments.
  • Wetlands categorized as “enhanced” or “restored” were noted as being wetter, with more open water for a longer time period compared to “natural” wetlands.
  • Correlations between rapid and detailed effectiveness monitoring showed that sites with a higher percentage of invasive plant species also scored lower for resident fish habitat and invertebrate habitat.

Data does not suggest that restored wetlands are functioning better or worse compared to natural wetlands.​

  • Additional information may be necessary to describe accurately pre-wetland function and condition to improve the ability to report on the effectiveness of wetland restoration and mitigation actions over time.
  • Variation in macroinvertebrate communities was so great between sampling years that rendering a robust I-IBI was not possible. Additional sampling is needed to evaluate the feasibility of producing a reliable I-IBI.

These methods when further developed and refined are intended to provide the framework for an Oregon Wetland Effectiveness Monitoring Guide. Monitoring will continue at these sites over time to provide more insight into the long-term effectiveness of various wetland actions. This monitoring may also be replicated in other areas of Oregon such as the north coast and eastern Oregon.

Significant effort was devoted to improving accuracy and completeness of existing database and GIS information of previous mitigation actions. These improvements will allow for timely reporting of wetland conditions and function. Mapping information is intended to be shared on Oregon Wetlands Explorer in the future.

OWEB will reconvene the wetland planning project team to help distribute this information and gather support for continuing development of understanding wetland function and condition in Oregon.​