In 2001, the Oregon Department of Fish and Wildlife (ODFW) conducted habitat surveys in Fanno Creek Mainstem, North Ash Creek, South Ash Creek, Woods Creek, and Vermont Creek. Physical habitat throughout all these subwatersheds has been altered due to development. Riparian corridors are generally narrow and vegetation cover is low along much of the creeks. The creeks do not substantively interact with the floodplain. In-stream habitat suffers from lack of structure (e.g., wood, boulders) and high proportions of sand and silt substrate, contributed by eroding stream banks due partly to increased stormwater runoff from upland development. Fish passage is severely constrained by numerous culverts.
Despite these conditions, the Fanno Creek Watershed is home to a variety of wildlife. Wildlife species most commonly observed are those that can tolerate a wide variety of habitat and the disturbance usually associated with residential and commercial development.
Furthermore, good habitat remains fragmented throughout the watershed. Riparian habitat in portions of Fanno Creek Mainstem, Woods, and Vermont creeks contain relatively wide, connected, and vegetated riparian corridors. Good channel habitat and stream structure can be found scattered throughout the watershed, including Fanno Creek mainstem near SW 45th Avenue and portions of Ash Creek.
Fanno Creek Mainstem
While urban development has degraded habitat throughout the subwatershed, opportunities for protection and restoration exist. Riparian habitat is relatively good below Oleson Road and between 45th Avenue and 39th Drive, in some cases yielding a functioning riparian corridor. In-stream habitat is also relatively good in places, providing critical rearing and refuge habitat for fish in winter and summer.
Riparian integrity and wildlife habitat upstream of SW Shattuck Road is impaired due to development and road crossings. Very little riparian vegetation remains and shade cover is lacking. Floodplain connection is also poor above SW Shattuck Road. Road culverts disrupt stream connectivity and likely isolate resident fish. Channel conditions and habitat structure have not been well documented.
Despite development, riparian integrity and habitat is considered fair to good downstream of SW Shattuck Road. Floodplain conditions are also relatively intact downstream of SW Shattuck Road. An undeveloped patch of forest exists near SW 61st Avenue. Channel conditions have not been well documented.
Riparian habitat and connectivity is impacted by roads, homes, and private landscaping in the lower and middle reaches of the creek. Riparian habitat in Gabriel Park is protected but still impacted by recreational use. Numerous road culverts have disconnected the creek. In particular, the Vermont Street and 52nd Avenue culverts likely completely block fish passage. Over 70% of the banks are eroding throughout the creek. In-stream riffle habitat is degraded by fine sediment and organics overlaying the substrate, and is lacking overall in the lower and middle stream reaches. In-stream wood is severely lacking in the lower creek. While riffles are more common in the upper reaches of the creek, the habitat is covered with fine sediments and organics. Pools are also lacking in the upper reaches.
Despite development, the riparian corridor habitat is relatively good, particularly in the upper creek reaches in Gabriel Park. Established conifers and deciduous trees are common. A number of beaver ponds are scattered in the lower and middle reaches of the creek, in which resident fish likely rear and seek refuge. The upper reaches of the creek are relatively protected in Gabriel Park, and large woody debris is abundant. Quality in-stream pools in the lower and middle creek reaches provide limited refuge for fish. Generally, in-stream fish habitat is considered marginal.
Riparian habitat and connectivity is impacted by development, particularly in the lower and middle reaches of the creek. Floodplain interaction is very limited. Numerous road culverts and a dammed pool at the Portland Golf Club have severely disconnected the stream, preventing fish access to some isolated good habitat. In-stream riffle habitat is severely lacking in the lower and middle stream reaches and silt covers much of the substrate, degrading the habitat. While riffle habitat is better in the upper portions of the creek, pool habitat is lacking.
Despite development, the riparian corridor habitat is relatively good. In the lower and middle portions of the creek, large conifers and hardwoods are common and numerous springs, seeps and wetland habitat exists near Oregon Episcopal School. In the upper portions of the creek, riparian habitat is very good and tree canopy cover averages 74% within 30 feet of the creek. Much of the upper portions of the creek are within an open space tract. Banks are stable all along the creek, indicating properly functioning conditions. In-stream habitat is good in places. Upper portions of the creek likely contribute woody debris, nutrients, and macroinvertebrates to lower portions of the creek.
North Ash Creek
Riparian habitat and connectivity is impacted by development. The effective riparian corridor does not extend beyond 30-65 feet of the creek. Development and landscaping near the creek has reduced floodplain interaction. Banks in the middle of the creek are actively eroding. Four road culverts east of Multnomah County impair stream connectivity; nearly one-quarter of the mainstem is piped. Additionally, the creek is disconnected from Ash Creek and Fanno Creek by an in-stream structure and dammed pool near the confluence of Ash Creek. Stream banks are slightly eroding. In-stream habitat lacks wood and pool area is low and degraded by fine sediment.
Despite development, the riparian corridor is fairly wide and consistent. Dominant plant species include second growth deciduous trees and shrubs. Tree canopy cover averages 58% within 30 feet of the creek. Additionally, a wooded residential development provides a relatively extensive forest canopy between SW 52nd and SW 57th Avenues. The creek interacts with the immediate floodplain. In-stream habitat includes abundant quality riffle habitat and a small portion of pools. Pools likely provide important protective cover. Summer low flows in North Ash Creek are about 0.02 cubic feet per second.
South Ash Creek
Riparian habitat and connectivity is impacted by homes, which often abut or cross the creek, roads and trails. Shade cover over the creek from large canopy trees is lacking. The creek only occasionally interacts with the immediate floodplain. Banks are eroding all along the creek. Stream connectivity is impaired by seven road crossings. The SW 62nd Avenue culvert is believed to completely block fish passage. In-stream cascades and steps may also limit stream connectivity and resident fish movement. In-stream habitat lacks wood and pool area is relatively low.
Riparian vegetation is considered good along most of the creek. Mixed conifer and deciduous (second growth) trees, and grasses are common. Tree canopy cover is about 96% within 20 feet of the creek. The creek occasionally interacts with the immediate floodplain. In-stream habitat includes good riffle and pool habitat. Pools likely provide important cover and rearing habitat for resident fish. Several large open spaces are located above SW 55th Avenue, which may be potential restoration sites.
Red Rock Creek
The headwater reach of Red Rock Creek is highly constrained and steep. Floodplain interactions are limited. Aerial photos and observations indicate that the riparian zone is narrow. The creek is fragmented by SW 68th Avenue and at Interstate 5. Neither has been evaluated for fish passage, but both are expected to completely prevent fish movement. Habitat characteristics have not been well documented.
Despite development, a narrow riparian corridor exists along portions of the creek. Vegetation cover is highest in the south and central portions of the subwatershed. An open space tract is located along SW 59th Avenue. A small wetland pool exists at the downstream of SW 68th Avenue, outside the city. Generally, creek flow is considered adequate in this headwaters reach to support a viable riparian fringe. Red Rock Creek is considered perennial, but it is likely that the tributaries east of Interstate 5 are seasonally intermittent.