2.8      Physical Habitats within the Johnson Creek Watershed

2.8.1	Upland Habitat
2.8.2	Wetlands
2.8.3	Riparian Areas
2.8.4	Instream Habitat

The Johnson Creek watershed contains a mosaic of vegetation types, including agricultural lands, urban and suburban landscapes, upland forests, riparian woodlands, and wetlands. Remnants of predevelopment vegetation are rare, as a result of extensive logging and clearing (Portland Bureau of Planning, 2001). The following is a summary of the various habitats (upland, wetland, riparian, and instream physical) that make up the Johnson Creek watershed and their baseline conditions.

2.8.1       Upland Habitat

The forest that historically covered the Johnson Creek watershed ridges and lowlands was mostly cleared in the early 1900s for agriculture, timber production, and urban uses. In the mid and late 20th century some areas such as the buttes and ridges in the south central and eastern part of the basin were left to regenerate into a second growth forest. Forest clearing of second growth has increased dramatically in recent years as housing development expanded from the lowlands onto the ridges and hillside slopes. Presently, about 57 percent of the watershed is vegetated including all types such as, but not limited to, grass, trees, or blackberries (Portland Bureau of Development Services, 2003).

The Johnson Creek watershed straddles the border between the Willamette Valley vegetation zone and the Western Hemlock zone (Franklin and Dyrness). The upland forest community exhibits characteristics common to both of these zones. The prominent occurrence of western red cedar and the presence of hemlock suggests that the forest is best characterized by the Thuja plicata/Acer circinatum/Polystichum munitum (red cedar/vine maple/sword fern) community of the Western Hemlock zone. The Willamette Valley Pseudotsuga menziesii/Acer circinatum/ Polystichum munitum (Douglas fir/vine maple/sword fern) community is similar though cedars are less common associates. Both of these communities frequently occur on north slopes such as those that make up the Boring Lava Domes and other buttes. The Boring Lava Domes area is more heavily forested than most of the watershed. The Lava Domes forest generally ranges from 40 to 100-year old second growth stands in a mid-successional stage referred to as conifer topping hardwood. Certain areas in the watershed, however, contain much older forest stands with tree diameters reaching five feet or more (Portland Bureau of Planning, 1998).

Upland forests in the watershed are typically comprised of a mixed conifer/deciduous forest with western red cedar (Thuja plicata), bigleaf maple (Acer macrophyllum) and Douglas fir (Pseudotsuga menziesii) frequently occurring as dominant tree species. Other occasional dominant trees include red alder (Alnus rubra), western hemlock (Tsuga heterophylla) and black cottonwood (Populus trichocarpa).  Dominant shrubs in the forest community include vine maple (Acer circinatum), western hazel (Corylus cornuta), Indian plum (Oemleria cerasiformis) and snowberry (Symphoricarpos albus). Common herbaceous plants include western sword fern (Polystichum munitum), Oregon grape (Mahonia sp.), and fringecup (Tellima grandiflora).

Johnson Creek acts as a wildlife corridor for the passage of species not normally observed in large cities, including deer, coyote, bear, cougar, and many woodland and meadow birds (Portland Bureau of Planning, 1998).  Pileated woodpeckers have been observed in the Boring Lava Domes forests.

2.8.2       Wetlands

Over time, development and associated changes to the landscape has highly impacted wetlands within the Johnson Creek Watershed.  No accurate estimate of the total acreage of wetlands prior to European settlement exists but there has been a substantial reduction. The remaining wetlands are extremely diverse in nature, and include forested, scrub-shrub, emergent, wet meadows, and open water (aquatic) vegetation types. Wetlands within the watershed range in size from the 19-acre Beggars Tick marsh in the Lents area, to numerous diminutive emergent wetlands in the basin of less than a tenth of an acre (Adolfson, 2000).

Forested wetlands within the Johnson Creek watershed are dominated by western red cedar (Thuja plicata), Oregon ash (Fraxinus latifolia), Pacific willow (Salix lasiandra), or red alder (Alnus rubra). Scrub-shrub wetlands within the watershed are dominated by Pacific willow, Piper’s willow (Salix hookeriana), or hardhack (Spiraea douglasii). Emergent wetlands within the watershed are dominated by common cattail (Typha latifolia), colonial bentgrass (Agrostis capillaris), reed canarygrass (Phalaris arundinaceae), stinging nettle (Urica dioica), jewelweed (Impatiens noli-tangere), creeping spike-rush (Eleocharis palustris), common rush (Juncus effusus), or slough sedge (Carex obnupta). Wet meadows within the watershed were dominated by common rush, creeping spike-rush, dagger-leaved rush (Juncus endifolius), reed canarygrass, or meadow foxtail (Alopecurus pratensis).

Several of the larger wetlands within the watershed contain intact native vegetation and have moderately mature, mid – to late successional vegetative communities. However, many of the wetlands in the watershed have non-native and invasive plant species that dominate most or all of the wetland. Human-made wetlands include shallow drainage channels and excavated ponds of various sizes (Adolfson, 2000). Spring-fed wetlands are commonly associated with the numerous terraces found throughout the watershed but particularly along Crystal Springs Creek.

Two major groups of wetlands exist within the watershed: The first group of wetlands are those associated directly with the hydrology of Johnson Creek and its tributaries. These wetlands tend to be located within the 100-year floodplain and often in very close proximity to the creek or tributary channels. These wetlands are often cut-off meanders from the creek, terraced wetlands, or lowlands that receive overland flows from the creek and are fed by shallow sub-surface flows or groundwater. The second major group of wetlands are small hydrologic systems in and of themselves that either drain into Johnson Creek directly or contribute to the creeks’ annual flow through groundwater recharge. These wetlands are found in Errol Heights, Beggars Tick marsh area in Lents, and the Saddle area in Pleasant Valley. These systems function more or less independently of Johnson Creek, and contain spring and seep-fed hydrology, which tends to create high quality aquatic ecosystem. The springs and wetland in Errol Heights, in particular, are directly connected to the hydrology of Johnson Creek, providing overland drainage directly to the creek.

Many wetlands in the basin have good connectivity with undeveloped open space, upland habitats, and the Johnson Creek riparian corridor. Several significant areas of wildlife breeding and nesting are found in wetlands within the basin with dense breeding populations of amphibians, including red-legged frogs (Adolfson, 2000).

2.8.3       Riparian Areas

The riparian corridor along Johnson Creek and its tributaries varies in width, from extensive vegetated areas over 600 feet in width to reaches with little or no vegetation along the bank. The most extensive vegetated riparian areas in the drainage basin are in smaller headwater creeks in the Boring Hills south of Powell Butte on either side of the Gresham/Portland urban services boundary (Portland Bureau of Planning, 2001). On the mainstem, reaches 12 and 16 and parts of 13 and 14 have the largest forested riparian areas. In Gresham, the most extensive and intact riparian area is located upstream of Regner Road (McMonnaha 2002). The tributaries with the most heavily forested riparian areas are Mitchell, Badger, Sunshine, and Deardorf/Wahoo Creeks. Crystal Springs and the lower reaches of Johnson Creek (near the Milwaukie/Portland boundary) have the least extensive riparian vegetation. The Boring Lava Domes area is more heavily forested than most of the rest of the watershed. By comparison, the headwater streams flowing through rural and agricultural lands in the upper watershed have very little riparian vegetation.

Riparian areas within the Johnson Creek watershed consist primarily of mixed forest with some coniferous forest and shrub areas. Forested riparian areas within the watershed include Douglas fir (Pseudotsuga menziesii), western red cedar (Thuja plicata), black cottonwood (Populus balsamifera trichocarpa), and red alder (Alnus rubra) as dominant tree species. Other common tree species within the watershed include Oregon ash (Fraxinus latifolia), big-leaf maple (Acer macrophyllum), and Pacific willow (Salix lasiandra). Shrub habitats within the watershed include Himalayan blackberry (Rubus discolor), red-osier dogwood (Cornus sericea), hardhack (Spiraea douglasii), red elderberry (Sambucus racemosa) and salmonberry (Rubus spectabilis).

Sensitive species known to occur in the riparian areas of Johnson Creek include three salamander species (long-toed, northwestern, and Columbia), two frog species, and one toad species. Painted turtles have been identified in the upper watershed (east of 162nd Avenue) (Adolfson, 2000).

Riparian vegetation is either narrow, minimal or lacking throughout much of the watershed. Interestingly, riparian vegetation is as lacking in the upper watershed as it is in the lower watershed. Generally, existing riparian vegetation consists of areas dominated by blackberry or young native plants and lacks large mature trees. However, vegetation quality is improving as cities, other local agencies, and citizen groups have ramped up efforts to remove invasive and non-native plants and replant natives and as vegetation begins to grow and create more canopy closure. The highest quality riparian vegetation is found within Reach 16, in Gresham upstream of Regner Road (McConnaha 2002). In fact, the largest amount of intact riparian vegetation throughout the Johnson Creek drainage basin is found in the City of Gresham. The ODFW 2000 report noted the following comments concerning Reach 16: “Reach 16 is dominated by mixed coniferous and deciduous trees with a dbh of 50-90 cm, with few larger trees, and unlike the previous downstream reaches, this riparian zone exhibited favorable characteristics continually throughout the reach.” The riparian findings of the ODFW assessments are summarized in table format in the Action Plan in Appendix B (PDF, 83 KB).

2.8.4       Instream Habitat

The channelization of Johnson Creek has had a significant impact on the quality of instream physical habitat. Because the historical floodplain of Johnson Creek is disconnected or minimally connected through much of its length flood flows cannot spread out and attenuate on the floodplain. Rather they are directed and concentrated into the main channel, increasing scour and degrading instream habitat. In addition, disconnection and fill in the floodplain has eliminated off channel habitat along the mainstem. With the exception of the Brookside constructed wetland off-channel habitat is extremely rare in Johnson Creek (McConnaha 2002).

The ODFW findings generally indicate that Johnson Creek has extremely low wood volumes in stream, particularly large wood that is necessary for pool formation. This is due to the lack of large, mature riparian trees and active removal of woody debris from the creek by citizens and officials from city agencies trying to prevent obstruction of flows downstream (McConnaha 2002). ODFW also found a high percentage of hardened banks, lack of refugia through many reaches, channel incision, and high levels of fine sediment. The ODFW report found Reach 16 to have the highest quality instream channel habitat structure with the following description:

Multiple channel units with good complexity occur upstream of Regner Road, and downstream of Hogan Road.  The complexity at Hogan Road is very diverse, and has many large woody debris jams associated with deep pools and multiple channels.  Reach 16 contains the greatest refuge potential that we found within the main stem survey. This is due to the presence of large woody debris, backwaters, deep pools, and shade cover. Reach 16 is the most natural and the least disturbed setting found on Johnson Creek in the 1999 survey.

ODFW also found that glides, which are generally uncommon in natural, healthy creeks, are widespread throughout the creek. This is an indication of the quality of instream habitat and is likely due to the deficiency of instream wood, a key element in breaking glides into pools and riffles. Existing pools and riffles are created not by woody debris but by existing geomorphic features that have evolved as energy is dispersed along the stream course (McConnaha 2002).

Habitat assessment of Kelley Creek reveals that there are a few small sections of higher quality habitat, while much of the creek is impacted or degraded. Most impacts are due to the lack of high quality riparian habitat and large quantity of stormwater draining to the creek as a result of tiling and other agricultural practices (ODFW 2000, BES 2001). Crystal Springs habitat is degraded as well. Much of the creek has been channelized and lacks healthy riparian buffers. The instream habitat findings of the ODFW assessments are summarized in table format in the Action Plan in Appendix B (PDF, 83 KB).

The Portland ESA Program assessed baseline conditions for habitat indicators in Johnson Creek (See Table 5). These indicators and their assessed base line condition compared to properly functioning conditions were incorporated into an Ecosystem Diagnosis & Treatment (EDT) Model. See Watershed Problems and Opportunities in Chapter 2 for discussion of this model and results of selected indicator attributes and their protection and restoration values.

Table 5. Habitat Indicators in the Johnson Creek Watershed

Source: Portland ESA Program and modified by Adolfson.