Griffin Creek is a predominantly forested sub-basin that flows for approximately ten miles in a southwesterly direction from its headwaters before turning northwest roughly three miles before its confluence with the Snoqualmie River. All of the forestry areas in the sub-basin are under private ownership. According to the 2001 land-cover analysis by Marshall and Associates, 13.2% of the sub-basin is classified as either “recent clear cut forest” or “recently regenerated forest”, second only to the neighboring Tokul Creek sub-basin.
Like many other tributaries in the watershed, the lowest reaches of Griffin Creek are within the APD which includes portions of the Snoqualmie’s 100-year floodplain. Upstream of the APD, roughly 1.5 miles lies within a rural residential land use designation, an area that includes King County’s Griffin Creek Natural Area. The transition from agricultural to rural residential land use is marked by a crossing of the Snoqualmie Valley Trail as it traverses Griffin Creek along a trestle.
Although Chinook salmon utilize the lower reaches of Griffin Creek, it is known primarily as a thriving steelhead and coho salmon stream, with both species ascending well into the headwaters. In the forested reaches, riparian vegetation is primarily composed of native species (King County, 2002).