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Regulations & Permits > Reporting requirements > Stormwater monitoring > Stormwater Action Monitoring > SAM effectiveness studies > Paired watershed retrofit and restoration

Paired watershed retrofit & restoration study

The City of Redmond led this 10 year study to understand how large scale stormwater retrofits affected small urban streams. Seven watersheds in and around Redmond were monitored for hydrology, water quality, habitat, and biological indicators. There are three watershed types in this study design:

  • Three application watersheds: Evans, Monticello, and Tosh
  • Two reference watersheds: Colin and Seidel
  • Two control watersheds: Country and Tyler's

Application watersheds will undergo large-scale retrofits to bring the watershed into current Washington stormwater management standards. Control watersheds will progress at a normal timeline of development. Reference watersheds will not develop as they are in relatively protected environments.

Study question

  • How effective are watershed-scale rehabilitation efforts at improving conditions for small stream receiving waters?

Scope of work

The monitoring in this study ran from 2015 to 2025. Because of its length, only major tasks and deliverables are summarized here.

Planning and preparation

Study findings

Water Year Data Reports

Each year, this study produced a data report that summarized all monitoring results collected during the previous water year (October through September). These reports also documented any data quality issues and noted how those issues affected data use or interpretation. They also described the rehabilitation work completed by the City of Redmond or King County during that year.

Water and sediment chemistry data are stored in Ecology’s Environmental Information Management (EIM) system and made available under study ID RSM_EFS1. Flow and temperature data are available by searching “RPWS” on King County Hydrologic Information Center website.The appendices in the annual reports include several incremental deliverables, such as hydrologic summaries, King County’s data quality assurance reviews, water quality summaries, and sediment quality summaries.

Trend Reports

In years 4, 8, and 10 of the study, trend analysis reports to go along with the annual data reports were produced. These reports summarized statistical analyses of all monitoring data collected up to that point. The purpose was to look for long‑term patterns and identify whether completed rehabilitation work was associated with changes in receiving water conditions. Each trend report presents the major findings and conclusions from these analyses.

Pond retrofit sub-study

Street sweeping sub-study

Contact information

Chelsea Morris
Stormwater Action Monitoring Scientist
chelsea.morris@ecy.wa.gov
564-999-3052