There are a large number of "social trails" as well, which often climb steep, unstable slopes, increasing erosion and overall stream degradation. Every part of the creek is accessible, but the lake has some parts where it's not. There are people living along the lake in houses, and so that part is theirs. The geology of the Boeing Creek's watershed is dominated by sands, gravels, and silts created during the last glacial period. Materials present include subglacial tills made up of silt, sand, and gravel particles; advance outwash deposits, made up of well-sorted sands and gravels; and transitional beds, made up of compacted clay, silt, and sometimes sand. Salmonid use that has been documented in Boeing Creek include chinook ("Oncorhynchus tshawytscha"), chum ("Oncorhynchus keta") and coho salmon ("Oncorhynchus kisutch"), and sea run coastal cutthroat trout ("Oncorhynchus clarki clarki"). A study done in 1994 found juvenile coho salmon in the lower portion of Boeing Creek, below the Seattle Golf Course Dam. The same study found cutthroat trout in most of Boeing Creek, up to the King County M1 R/D pond, near the creek's source. The Salmon Watchers Program have observed a site on river mile 0.1 of Boeing Creek since 2000. Coho and chum salmon are commonly seen, with fish counts ranging up to 160 chum salmon in 2003 and 89 coho salmon in 2001. Two chinook salmon were observed in 2000. Fish populations are hindered by two storm water detention systems: the M-1 Dam (or "Boeing Creek Detention Facility"), an in-stream retention device on the main fork, and the Retention-Detention Ponds, an off-channel system in Boeing Creek Park. Three other structures influence stream ecology: Hidden Lake and its associated dam; an artificial waterfall, about ten feet high, constructed from concrete, just downstream from Innis Arden Way; and the "Seattle Country Club Golf Course Dam", a metal dam and pump station about 200 meters downstream of Innis Arden Way, which forms of reservoir that supplies the Seattle Country Club golf course with irrigation water. None of the dams provide fish passage and therefore present a total barrier, limiting stream use by anadromous species to the lower third of the creek. The riparian forest along Boeing Creek in Boeing Creek Park is an intact native ecosystem, mostly free of invasive species.