Dennis Chambreau
ESC 507
Winter 2001

BRINGING NATURE BACK TO SEATTLE

EDAPHIC RESPONSES IN EXPOSED LAKESIDE SOILS

Low winter water levels expose soils along Juanita Bay. Eagles like to roost in the cottonwoods.

INTRODUCTION

         Living in an urban area has many benefits. Cultural and economic reasons have led man-kind to develop urban areas of high population concentration for over 5000 years. One of the drawbacks to this concentration is the destruction of the natural environment that drew the people to the area in the first place. Seattle was an area of astounding ecological wealth that was recognized by the native population, but seen as economic treasure or production problems for the white man who came about 150 years ago. Seattle suffered some radical environmental degradation as people regraded, filled and cut to suit their needs. Although there were a few, including the native population, who were concerned about this damage, it was not until recently that some of the benefits of the former ecology were appreciated. Today it is more common for the white man to revere the natural processes, and many government and private groups are taking steps to preserve, enhance, and create areas of natural vegetation for human satisfaction, ecological health and wildlife. Unfortunately, within the Seattle urban area there is little of nature left. Nature is confined to the few places that have been undeveloped because the sites are unsuitable for building, usually because of soil conditions that make development difficult. The wetland soils exposed by the draining of Lake Washington in 1916 are included in these areas. These old lakebed soils give us the opportunity to return a little of nature into our urban environment. These areas, though, are limited in the kind of natural processes that develop on these soils. Edaphology is a little used word that implies study of soils from the standpoint of higher plants. Old lakebed soils in these mostly saturated areas will provide habitat for wetland species that are not necessarily amenable to human activity. Much of the natural vegetation that existed around these areas had been removed, to be replaced by imported ornamentals and weeds. The problem becomes how to accommodate the new-found reverence for nature in these disturbed and somewhat unnatural settings.
        This project looks at how humans, vegetation and soils interact in two of these areas created by lowering the water level of Lake Wasington. Both Union Bay and Juanita Bay are now designated as Natural Areas. Union Bay is highly disturbed and is still very much a project. Juanita Bay is much less disturbed and is now only being tweaked. These two areas have a very different history, but have similarities and it is interesting to compare how the natural processes and humans are progressing together in these urban area.
         These areas share the very interesting geological history of Lake Washington. This lake was formed by glacial gouging, and was a marine embayment of Puget Sound until about 13000 years ago when the alluvial fan of the Cedar River prograded across the south end, cutting off the bay, and turning it into a freshwater lake. The Black River was the natural drainage, connecting with the Green and Cedar rivers at the south end of the lake to empty into Puget Sound. The lake remained fairly stable for the next 4-5000 years, allowing the build up of peat deposits in the Union Bay and the Mercer slough areas. These peat deposits have been dated as starting about 11900 years ago. Flooding from the Cedar River sometimes entered the lake, and the level of the lake fluctuated seasonally up to approximately seven feet. In 1916 the Montlake cut lowered the lake, drying it's natural outlet at the Black River and changing the outflow through Lake Union and Salmon Bay. Building the dam at the Chittenden Locks raised the water level, making the net lowering about 9 ft. The areas we are discussing were now exposed to their current level, although the lake level is managed by the dam at the locks, and there is a winter drawdown of about 2 ft.

JUANITA BAY

Original shoreline at Juanita Bay

Juanita Bay was home to the Tabtabyook people who lived on the south shore of the bay where the Indianola soils were exposed. The wetland areas provided them with wapato and cattails for food and mats. Duck from the marshes along the bay were another important food species, providing meat and eggs. The white man came in the 1830's as fur traders bringing smallpox, which devastated the local people. The settlers didn't arrive until about 1880. Logging was the first activity in the area, and Juanita Creek was dammed for a shingle mill. There was likely increased sedimentaion at this time, although the salmon still spawned in the marshland around the bay. A bridge was constructed across the Forbes Creek slough in the 1890's. In the early 1900's a dock was built in the bay for steam ferries which continued to run until the lake was lowered. The less populated east side of Lake Washington was a popular excursion site for Seattle residents. Duck hunters found good luck here. In 1916, the bay became too shallow for the ferries after the lake was lowered, and the salmon spawning was destroyed. 116 acres were added to the area when the lake was lowered. A fill and bridge spanned the slough in 1932. A golf course was constructed on the old Tabtabyook village site between 1927 and 1932, with fairways extending on fill over the saturated soils exposed in 1916. The area experienced increasing urbanization over the next decades. In 1975 the golf course closed and the area was acquired by the City of Kirkland as a park in 1984. Over the coming years the park was developed with the help of Federal and State money, and especially the Washington DNR Aquatic Lands Enhancement Account. The direction of the park was to enhance and maintain a Natural area for the benefit and enjoyment of residents and visitors. Currently the East Lake Washington Audubon Society among others are planting native plants to further enhance the area.

SOILS

Juanita Bay has been less disturbed than Union Bay. Forbes Creek and Juanita Creek still empty into the bay, adding some mineral sediments to the organic soil material. The shallow bay has some interesting soil features, having Indianola sand at the mouth of Juanita Creek, making for a nice beach. Nelson Point is a bar of sand and gravel built from erosive episodes and wave action, and perhaps related to a large earthquake 1100 years ago. The soils that were exposed are listed in the 1972 King County soil survey as Snohomish silt loam and Bellingham silt loam in the Natural area on the south and east shore and Indianola loamy fine sand in the north shore at the County beach. Nelson Point, along the southwest shore is listed as an Indianola. These are alluvial soils from deposits from Forbes and Juanita Creek. Although unreported on the survey, the drained areas are peat rich and might be classified as Seattle series. The saturated soils along the south shore where the golf couse was were repeatedly filled with cedar bark, sawdust and imported soils in an unsuccessful effort to keep the golf course from sinking into the lake due to the oxidation and compression of the peat-rich soils. Berms and pumps were also used during the life of the golf course. Presently the soils are generally saturated year round due to the low elevation, and the ponding from the beaver activity in the area

VEGETATION

Beaver dams cause mortality due to soil saturation in a wooded wetland with an invasive canary grass understory

The vegetation developing here is a combination of natives and non-natives. A cursory glance of the area note some different general areas. There is the cattail dominated shoreline, a native emergent area. There is a large area dominated by canary grass, a non native on seasonally saturated soils. There is the willow, spirea, cornus shrub area, and an alder-cottonwood-willow wooded wetland. These areas are designated by the water levels in the soils being progressively lower. The cottonwoods are highly successful invaders of the area where the soils have a slight elevation. Juanita Bay can be generally regarded as a native dominated area, although the canary grass and blackberries completely dominate large areas. The only vegetation management activites have been cutting blackberries and planting native trees and shrubs to favor birds.

SOCIAL ASPECTS

The problems involved in making these areas accessable to humans are solved by restricting visitors to elevated walkways that lead to viewing areas. The 1932 roadway has become a popular walkway. The focus now is use as a wildlife viewing area. The East Lake Washington Audubon society has birding days, and the Kirkland Park Department has volunteer rangers to lead groups through, explaining the wetland ecology and wildlife uses. Juanita avoids a huge problem that Union Bay struggles with by utilizing the high areas of the old golf course as a viewing area and open park. Unlike Union Bay, there is no effort to reclaim this area with natural vegetation.

The future for Juanita Bay would seem to be stability of what is now present. Plantings and attractants for ospreys and other birds are on the agenda. Blackberry control is everpresent. Management levels are low as would seem proper for a natural area. Expansion into the recently acquired Forbres Creek area will further enhance the site, bringing an upland natural area into the mix. This combination of wetlands and uplands will expand the natural diversity of this area.

UNION BAY

Original shoreline at Union Bay

Union Bay is an example of the radical changes people in the Seattle area made to their environment. Originally the outlet of Ravenna Creek and Green Lake, this was changed when Ravenna creek was diverted to the West Point Treatment facility at Discovery Park, cutting off any alluvial sedimentation. The University of Washington moved to the area in 1913. When the lake was lowered these exposed soils became a marshy area that was was beginning to acquire a shrubby wetland vegetation. Around 1926, Union Bay was loaned by the UW to the city of Seattle to be used as a land fill for city garbage disposal. A 1959 plan for the area still extolls how the Univerity was acquiring potentially valuable land so cheaply. As the "swamp" was filled, it was covered with topsoil from various sources, and converted to parking areas, housing and athletic fields. The piling of refuse and soil raised the area up to 30 feet above the level of the lake. When the landfill was closed in 1965, the remainder was covered with inported soils, graded, and in 1971 planted with pasture grasses. By now the UW had discovered that the unstable nature of the underlying peat and the dramatic settling restricted many uses of the area. In 1974 it was proposed that the remaining undeveloped area be utilized as an arboretum, and steps began in that direction. The Landscape architecture firm of Jones and Jones developed a plan for the area in 1976. Because the refuse and topsoil continues to compress the underlying peat layer, it is estimated that the lake will eventually reclaim 30 acres of the 166 acre landfilled area. In 1989 the EPA designated the area as a C1 hazardous waste area, which meant that hazardous wastes were comfirmed to have been disposed of at this site. In the 1990's the site was designated as the Union Bay Natural Area, with a progressing set of goals. In 1992 Pentac Environmental designated wetland areas. The plan will allow these wetlands to develop as subsidence continues. The plan calls for keeping the pasture grass areas open, and trying to convert it to a native shrub-steppe area. The plan will have scattered native woodlands, but restrict their location to some higher elevation, around the wetlands and in the Unmanaged Wildlife Area. Roads will hopefully be eliminated, and trails maintained.

SOILS

Soil conditions are mostly of an inconsistant nature, being a heterogeneous fill. This cap of soil has been measured to be between 1.5 to 18 feet thick. The grasses have developed a thin A horizon averaging no more than 8 inches in a silty to clay loam, overlying a gleyed B horizon. Ten soil samples taken in 1998 range from sandy loam to clay loam. The pH ranged from 4.8 to 7.8. These soils tested low in organic matter at 2% to 6% with only one at 11.8%. The uneven nature of the settling of the area is leading to pockets of ponded water separated by higher areas. Due to the weight of the refuse, the underlying peat was compressed and pushed out and up to the surface at the lakeshore where there was nothing to hold it in. Some of this material was dredged out, but there still remain some islands and an edge of peat soils along the shore of the lake.

Peat islands going native (plus loosestrife!) outside the managed area

VEGETATION

Present vegetation condition are mostly far from natural, showing decidedly the difference between the imported soils and the original peat. Most of the new marsh exposed by the lowering of the lake level never had time to develop a natural vegetation, as the land filling began in 1926. The native vegetation matrix outside the area had given way to residential and university development, and could not simply move back in. The uneven settling creates a mosaic of different soil moisture regimes. Along the present shoreline, especially where the peat is exposed, the native and invasive species dominate in a regime that is too saturated for the pasture grasses. Cattail dominate the shore, giving way to native spirea, willow, and other shrub vegetation in a band along the shore. In the remainder of the area the planted grasses dominate, along with the everpresent invasive blackberry. There are a few areas of cottonwoods and willows, the most agressive invaders on the less saturated sites.On the west side of the area willows and cottonwoods form a native thicket of wooded wetland on the area that was not subject to the landfill activity. This could be seen as a natural progression that may have occured. Various restoration projects have planted native species in plots scattered about the site. Willow and cottonwood volunteers continue to try to invade.

SOCIAL ASPECTS

Restoration ecology students and hikers An eagle roosts in a dead cottonwood

The present use of the site is for university research and recreation. Hikers, joggers and bikers use the trails and can view wildlife such as many duck species, herons, eagles and beavers to name a few. The pasture grass areas are kept mowed, giving a park-like setting. The natural plantings have yet to make a visual impact. There is a desire to keep the area open and park-like which may interfere with the desire for a natural setting.

The future should bring a slow development of native species to the area as restoration continues, but most likely it will be a managed natural area. The settling of the land into the lake will dictate a more wetland environment. This will probably neccessitate the building of elevated walkways. Reconnection of Ravenna Creek though not yet possible would make a great input toward a more natural setting.

DISCUSSION

        These wetland areas give us a chance to have a natural setting that works well for enhancing ecological health and wildlife, providing a recreational natural setting while utilizing umarketable land. What was only a side effect of lowering the lake can be turned into a social positive.
        It would seem that a "natural" area would have the smallest amount of input from humans. However in the urban area of Seattle, "natural" areas must be derived from nature and humans working together. Restoring the conditions that have been destroyed is not possible, and we must move on from some present starting point. There is not even the luxury of starting from our starting point of bare lakebed soils in 1916, but we must start 60 to 70 years later. The question is...how much intervention is needed?
         There are some differences in the vegetation present in these two areas for a number of reasons. Comparing the two sites can give us some ideas of the problems and solution we can look forward to. The main difference is that most of the soil at Union bay is imported and perched atop a refuse layer and are not subject to the influence of the lake water levels. Almost all the soils at Juanita are native to the area and saturated at one time or another. The Juanita Bay site has had more time to develop on natural soils and has developed without the competition of introduced pasture grass. Juanita has the huge benefit of a natural drainage system that channels the water in a naturally stable way. Beaver building dams on Forbes Creek further enhance the water regime. In Union Bay, however, there is no natural drainage for most of the area. The uneven settling has caused many hydrologic dead ends, forming unconnected ponds that dry in the summer, making it difficult for plants adapted to certain moisture regimes. Even if plants adapted to the present wet winter dry summer regime establish, they may be inundated as the land sinks. The stated purpose of keeping the Union Bay area open and " savannah-like" may be leading us down a road that will mean more human and less natural input.

Plants will try to grow almost anywhere they are given a little soil, some moisture and light. They will try to grow in any soil that they happen to be placed in. They don't have the luxury of moving on. There are soil factors that each plant species are adapted to. The relationship of a plant species and the soil are interwoven over time. Most soil series are mapped from vegetation types after a relation has been determined. Soils provide the habitat and needs for the vegetation, and the vegetation provides the habitat and needs for the wildlife. Wetland species are adapted to different soil moisture regimes. The level of the water is more important than the soil type. Water depth and the frequency of inundation are major factors in determining soil chemistry and thus the selection of species that will inhabit the area.

In nature there is a native succession of plants that will develop the ecology of a disturbed area. Any disturbed area will fill with species regardless of the hand of humanity. What plants move into an area depends on how they are adapted to the site, and whether there is a source for seed or vegetative dispersal. Succession can take a long time and consist of a number of species, or it can be short and dominated immediately by one species. Along the shore of both Union Bay and Juanita bay, agressive natives like the cattail have moved right in and dominated the site. Likewise with native spirea and willow brush and cottonwood, willow, and alder tree species in the saturated mineral soils. Natural succession seems faster in these saturated areas. It is a different story on the raised soils of Union Bay. Succession in these drier areas will be much slower. Succession also has a progressive effect on development of soils. Generally on bare mineral soils with little organic material such as was laid over the trash at Union Bay weedy tap-rooted species would slowly bring nutrients to the surface and develop an A horizon that would be suitable for the next succeeding species. Succession on the imported soils of Union Bay was not allowed due to the "state of the art" in the 70's when the quick solution of seeding pasture grasses effectively stopped any natural succession.
At Juanita and the wetter areas of Union Bay we see that nature seems to want to establish a cottonwood-willow-alder dense woodland at the edges of the saturated zone, with the shub willow dogwood spirea growing down to the edge of standing water where the cattails dominate. We can see at Juanita that these natural areas form a dense thicket are not amenable to human traverse, but are very suitable for wildlife, as human activity is restricted. At Juanita, this is remedied with elevated walkways. At Union Bay, there is a stated desire to keep large areas open, which favors humans and geese but few other species. Continued mowing restricts the natural succession of woody species that want to move in.

Willows and cattails are natural invaders on the original organic soils outside the fill.

SUMMARY

        The comparison of these two areas tells us that a natural hydrologic system providing a somewhat stable drainage system has more effect on the soils and vegetation in these natural areas than any other factor. The uneven settling of the soils at Union Bay makes establishment of a permanent wetland gradation from emergent to dryland almost impossible until the settling slows. The continuing variation in elevations will cause confusion in the natural succession of plants, and changes in the saturation and chemistry of the soils. Even the strange imported soils of Union Bay would settle into some natural gradation given time.
        The comparison shows us that the natural vegetation that will come into the native exposed soils creates a habitat that is not traversible by humans except on walkways.
        The desire to keep the open areas in Union Bay native means that humans will have to control the natural processes here, as nature will want to move in. At Juanita, there were fewer man made issues to deal with, and they started with a site that was already filled with a fairly natural succession of native vegetation with a few weedy imports. The open space problem is solved by leaving it out of the areas designated natural. Union Bay is an area still looking for a natural stability, and the emphasis is on native species. Juanita Bay has already reached some kind of accomodation with the human presence, and the plants that have moved in, albeit not all native. In our world where global distances are short, and species of plants as well as races of humanity are mixing in all locations, "nature" may not be restricted to what was indigenous, but to go with the flow with today's mixed natural processes. A new natural diversity. Humanity is a part of nature. Nature and humans together are looking for a balance between stability and change, management and freedom, urban and natural, natives and immigrants. These areas will always be managed to a certain extent.