Monitoring for adaptive management: status and trends of aquatic and riparian habitats in the Lake Washington/Cedar/Sammamish watershed (WRIA 8)

The objectives of the project were to:

(1) characterize conditions in small salmon streams using a spatially balanced, probabilistic sampling approach;
(2) investigate relationships between landscape, hydrologic, biological and habitat metrics;
(3) inform adaptive management actions recommended by the WRIA 8 Chinook Salmon Conservation Plan; and
(4) communicate findings, methods and analytical approaches to local and regional forums.

Data collected included habitat, fish composition, macroinvertebrate composition, hydrology, temperature, and land cover. Results included precision estimates (consistency of repeated measurements) of common habitat indicators, status and trend assessments, an analysis of land-cover/hydrology/habitat/biology relationships, and trend detection power analysis.

Findings:

• Stream biological conditions (as measured by the Benthic Index of Biotic Integrity or B-IBI) ranged from very poor in heavily urbanized areas to very good in rural, forested areas.
• Stream habitat conditions considered important for salmon (wood volume and water temperature) were found to be below standards considered supportive of salmon use even in rural areas. Wood volume was consistently below regional reference conditions and water temperatures frequently exceeded state standards.
• Specific metrics were identified that could be reliably measured over time and are recommended for use in a long term trend monitoring program. These metrics include important indicators of salmon habitat condition (wood volume, pool area, sediment composition, canopy cover, and B-IBI).
• For the most reliable metrics, it will take sampling annually for 10 to 20 years to reliably detect a 3 percent annual change in status or condition.
• Our study corroborated most other research on relationships between urbanization and benthic macroinvertebrate community condition as measured by B-IBI. Urban land cover and population density were the strongest predictors of declining B-IBI scores.
• Additional work is needed to establish properly functioning salmon habitat condition thresholds for relevant metrics that are specific to Puget Sound lowland streams.

Adaptive Management Recommendations: 

Certain salmon recovery priority areas located inside Urban Growth Area boundaries, where development and infill are occurring and forest cover is diminishing, appear to be at the most risk of further degradation in the short term. We recommend that the WRIA 8 Monitoring for Adaptive Management King County Science and Technical Support Section iv April 2015 Technical Committee and Salmon Recovery Council consider the following actions:

• Update the watershed evaluation first performed for the (2005) WRIA 8 Chinook Salmon Conservation Plan, based on the new information in this report and other sources.
• Based on a new watershed evaluation, re-examine management recommendations for all tier areas.
• Request regional support to develop condition thresholds for biologically relevant metrics specific to Puget Sound lowland streams.
• Implement an integrated and scalable monitoring strategy for the future.

Conclusions: 

One of the key elements of a relevant status and trends monitoring program is that it is sustained over time. The information presented in this study provides a solid foundation for the development of a well-designed and sustainable long term WRIA 8 status and trends monitoring program. These tools would benefit not only local watershed management, but the region as well. Future habitat status and trends monitoring that efficiently capitalizes on converging regional and local needs from multiple sectors (NPDES, salmon recovery, stormwater, etc.) would contribute substantially to a consistent and reliable long-term set of decision-making tools. 
 

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