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The Restore and Protect Project focuses on improving freshwater quality and addresses Puget Sound Partnership recovery goals related to protecting and restoring streams throughout Puget Sound. This project is part of a phased effort, and this report reflects work done in the second of five phases. For more information about the first phase of the project, see Strategies for Preserving and Restoring Small Puget Sound Drainages.

Streams are essential natural resources for humans and animals alike. Many of the animals that rely on healthy streams are especially sensitive to water quality and habitat conditions. This is true for well-known species like salmon, but it is also true for the many insects, worms, snails and other small critters that live on the bottoms of streams and often go unnoticed.  These smaller animals, often collectively called “stream bugs,” are excellent indicators of water quality and overall stream health. Collecting information about the number and types of stream bugs present at a site provides us with the big picture of how a stream is doing and what actions are needed to meet our water quality and habitat restoration and protection goals. 

Giant stonefly in the genus Pteronarcys
Stonefly in the genus Pteronarcys, a stream bug.

Goals

The goal of the second phase of the project is to identify human activities that are impacting a select group of streams and to recommend actions that restore and protect the stream basins, in order to advance the Puget Sound Partnership (PSP) overall goal of restoring, protecting, and sustaining Puget Sound.

This project looks at one of PSP’s Freshwater Quality indicators: the Puget Lowland Benthic Index of Biotic Integrity (B-IBI). This index is used to characterize stream health and is based on the variety of stream bugs present at a site. The B-IBI scoring system categorizes streams as “very poor” to “excellent,” on a scale of 0-100. This report focuses on four “fair” streams in need of restoration and 10 “excellent” streams in need of protection. These sites were selected from a long list of potential sites because of their history of B-IBI scores and their potential for improving or maintaining high scores. More information about the B-IBI scoring system and the criteria used to select sites can be found on the Puget Sound Stream Benthos website.

Side-by-side sampling in Soos Creek
Side-by-side stream bug sampling in Soos Creek.

Selected basins

Regional stream bug data were used to identify 10 healthy basins needing protection and four degraded basins needing restoration.

“Fair” sites include:

  • Illahee Creek, Kitsap County, Water Resource Inventory Area (WRIA) 15
  • Manzanita Creek, City of Bainbridge Island, WRIA 15
  • Stensland Creek, King County, WRIA 8
  • Tibbetts Creek, City of Issaquah, WRIA 8

“Excellent” sites include:

  • Lost Creek, Kitsap County, WRIA 15
  • Wildcat Creek, Kitsap County, WRIA 15
  • Chuckanut Creek, Whatcom County, WRIA 1
  • Margaret Creek, King and Snohomish Counties, WRIA 7
  • Big Soos Creek, King County, WRIA 9
  • Weiss Creek, King County, WRIA 7
  • Rock Creek, King County, WRIA 8
  • Cristy Creek, King County, WRIA 9
  • Newaukum Creek, King County, WRIA 9
  • Boise Creek, King County, WRIA 10
Restore and Protect Project Basin Location Map
Map of selected basins in the Restore and Protect Project (click or tap to enlarge)

Identifying stressors

Identifying specific stressors affecting stream communities is challenging. Many stressors known to impact stream communities, such as excess fine sediment, loss of riparian trees and shrubs, and flashy flows, are associated with increased urbanization and thus co-occur in most basins.

In this study, we identified potential stressors affecting each basin using data from field surveys and a variety of geospatial data. With this information, we characterized conditions at the local, riparian and basin scales and compared those to conditions we find in other stream basins.

To provide context for the site conditions, we used two approaches to generate a list of conditions that characterize typical “excellent” B-IBI sites and identify thresholds at which stream bug communities change in response to degraded conditions.

First, we examined the relationships between environmental conditions and B-IBI scores from additional sites within the Puget Sound basin. We also examined how sensitive stream bug species (independent of B-IBI scores) respond to degraded conditions. Second, we evaluated conditions at the local, riparian, and basin scale for each study site, and compared those to conditions observed in typical “excellent” sites.

What did we find?

We found what others have observed in studies evaluating the relationship between B-IBI scores and environmental conditions: multiple, related factors associated with urbanization and loss of forest are likely responsible for degraded stream health and negative impacts on B-IBI scores.

Changes in the stream bug community composition are best explained by large scale stressors (e.g., extent of urbanization in the basin and the associated stressors) rather than a single stressor.

At all “fair” sites, we found multiple conditions were degraded. Generally, conditions were most impacted at the basin and riparian scale, and in some cases, less at the local scale. These results corroborate other studies that indicate B-IBI scores are better correlated with basin-scale conditions than with site-scale conditions. 

As we expected, environmental conditions at “excellent” sites were much better than conditions at the “fair” sites. However, we were surprised to find evidence of multiple degraded conditions at most “excellent” sites. This suggests stream bug communities either have some resilience to degraded conditions, or the impact of the degraded conditions may be time-lagged. If so, their “excellent” status may be tenuous.

Cristy Creek stream survey
Cristy Creek survey

Recommended restoration and protection actions

Improving stormwater management and forest health will have a positive impact on the streams categorized as “fair.” This can be done by protecting intact forestland; establishing more forest cover; increasing the density of vegetation in, and the width of, riparian buffers; and controlling and treating stormwater as much as possible.

To improve local conditions at “fair” sites, stressors affecting conditions at the basin and riparian scale need to be addressed first. Restoration actions targeting site conditions, like reducing excess fine sediment, often require dealing with the source of the problem up in the basin or in the riparian buffer. Once the source of the problem is resolved, local conditions can be restored.

Recommendations for protecting “excellent” basins were highly variable and dependent on basin-specific conditions. Some basins were quintessential “excellent” basins that exhibited almost no degraded conditions and consistent “excellent” B-IBI scores. In these basins, we recommend protecting forests and limiting development to prevent future degradation. Other “excellent” basins had high B-IBI scores despite the presence of multiple degraded conditions. In these basins, we recommend improving stormwater controls, protecting and enhancing riparian buffers, and increasing forest cover throughout the basin.

Project documents

All documents are provided in Adobe Acrobat format.

Report

Maps

Supporting documents

For more information about The Restore and Protect Project, please contact Kate Macneale, Environmental Scientist, Science and Technical Support Section.