In the State of Our Watersheds report the Upper Skagit Tribe point to drastic increases in impervious surface and the impact it is having on salmon. The animations below show the shift in paved land in 1986, 2006 and (estimated) 2026.
The Skagit Chinook Recovery Plan recommended that impervious surface area be kept below a threshold of 7% in any tributary watershed. Increases in impervious surface area as result of development disrupt both ground and surface water ecology with negative consequences to stream health and productivity. Impervious surface has increased 25% between 1986 and 2006, with 79% of the increases occurring within the floodplain or in the catchments immediately draining into the floodplain.
If impervious surfaces continue to expand as they did from 1986 to 2006, impacts will intensify throughout the lower Skagit delta and floodplain. The core of Mount Vernon and Burlington will be heavily impacted by impervious surface (12-50%). Burlington east to Sedro-Wooley will be heavily impacted, and north and east from Sedro-Wooley will be potentiallyimpacted (7-12%). Impacts will also continue to intensify in and around Anacortes and along most of the shoreline of Fidalgo Island.