|
The purpose of this chapter is to characterize the physical, biological, and cultural conditions of the County's watersheds.
The San Juan and Gulf islands have been seasonally occupied by central coast Salish tribes from approximately 5000 years ago through the eighteenth century. According to tradition, the Songhees, Saanich, Lummi, and Samish all had winter villages in the southern Gulf and San Juan islands, as well as many permanent structures for other seasons (Suttles 1990). The seasonal and local availability of fishery resources had a great impact on population movements and settlement patterns of local Indian tribes. During summer months, populations commonly disbanded and dispersed to locations where resources were seasonally available. Small units of people left their winter villages and migrated to optimal fishing and plant gathering areas, where they resided in temporary lodges. It is thought that Native Americans influenced native grasslands and oak woodlands through the use of fire (Agee and Dunwiddie 1984). The population of native peoples of the San Juan islands declined by over 80 percent within 100 years of the arrival of Europeans, in 1774, due to the introduction of disease and the subsequent political removal of these peoples to mainland reservations.
Settlement in the islands began in 1850, when the Hudson's Bay company established a fish-salting station at Salmon Banks on the southern tip of San Juan Island. Bellevue Farm was established in 1853 as an agricultural station with over 4000 head of livestock. By the time American troops arrived on southern San Juan Island in 1859, native grasslands were already disturbed by the extensive grazing activities. Until 1872, the San Juan islands were claimed both by the United States and Great Britain. Military forces from both countries jointly occupied the islands until October 1872, when the San Juans became a part of the United States. Within 20 years settlers had spread to Lopez, Shaw, Orcas, Decatur, and Blakely islands, raising sheep, cattle, and poultry on small subsistence farms. Sheep farming was the most important livestock industry on the islands. Vegetables and fruits were also grown for markets on the mainland, with the advantage of easy transportation by boat, before roads provided access to markets in Seattle from mainland agricultural areas.
Extensive logging at the beginning of the 20th century removed all old growth and valuable timber on most of the islands. Establishment of the local lime industry also consumed great amounts of wood to run lime kilns, as well as young trees to make barrels for the lime. The lime company at Roche Harbor continued to operate until 1956. Quarrying activities for sandstone used for streets in Seattle were extensive on Waldron, Sucia, and Stuart islands. Fishing was a major industry in the islands, with canneries located at Friday Harbor and Deer Harbor. The recent collapse of the herring fishery, as well as the virtual shutdown of commercial salmon fishing due to population declines, has brought an end to the natural resource based economy that supported the island population in the past.
San Juan County's year-round population
is just under 13,000 people making it thirty-first in overall
population among 39 counties in the state. The fastest growth
in population in the San Juans occurred between 1970 and 1990
when the number of year round residents more than doubled (Figure
2-1, OFM). Growth in San Juan County was the fifth highest among
Washington counties for the period between 1980 and 1990, increasing
by 28 percent over the ten year period. During 1990 to 1995,
San Juan County population increased 22.6 percent and had the
second highest county growth rate in Washington State.
These numbers do not account for transient increases in population during the summer tourist season. Summer increases from visitors and part-time residents are generally three to four times the winter resident population, periodically bringing the county population to over 30,000 people (OFM). For instance, in January, 1996, the average daily passenger count for Washington State Ferries (WSF) traffic to the San Juan Islands from Anacortes was 1,173. But in August, 1996, a popular vacation month, the average daily passenger count was 5,367 (WSF 1999). Planes and tour boats account for additional summer visitors to the county.
The Washington State Office of Financial Management (OFM) forecasts that the county will grow in population between one and 1.5 percent annually from 1990 to the year 2010. The rate projected by OFM is substantially lower than the annual growth rates of up to six percent that the County has actually seen from 1990 to 1995. Although growth rates have slowed since the large increases between 1970 and 1990 (2.5 percent annually in the 1980s), growth has not leveled out to any appreciable extent. A continued growth rate averaging 2.5 percent per year between 1990 until 2012 would result in a winter residential population of 18,516 people by 2012.
Land cover describes the above-ground elements in a watershed that have a direct bearing on the infiltration of precipitation, erosion potential, and the wildlife habitat within a watershed. Cover is the summation of the vegetation and structures that intercept or direct water entering the watershed.
Naturally occurring land cover in the San Juan Islands includes second-growth conifer forests, hardwood forests, scrub and shrub plant communities, and open prairies. Rock outcrops and beaches are non-vegetated land cover types that occur naturally on the islands.
Vegetative cover absorbs the energy of falling raindrops, protecting bare soil from erosion-activating impacts. Intercepted rainfall flows slowly down the leaves, stems and roots of protective vegetation, infiltrating into the underlying soil or becoming surface runoff. Varying heights and densities of vegetation slow down the delivery of this rainfall to surface water runoff and groundwater systems. These delays result in lower peak flows of surface runoff, with reduced rates of soil erosion and sediment deposition. Rainfall runoff from the impervious rock outcrops is almost instantaneous, while infiltration of rainfall into sandy beaches is also instantaneous.
As areas of natural vegetative cover are replaced by low-intensity land uses such as pasture and hayfields, rainfall absorption and runoff patterns are modified. For instance, grass sod, with a lower water absorption rate than a forest duff layer, causes less rainfall to be absorbed into ground water and more rainfall to become surface runoff. In pasture, the diversity of vegetation is significantly reduced both in height and plant character (single blades of grass replace multi-branched, leafy vegetation). This reduction of vegetative diversity results in rainfall becoming surface runoff much more quickly, and can contribute directly to higher peak flows and increased erosion. In turn, increased erosion generates sediment which has the potential to plug the pathways to groundwater and contaminate streams.
As the intensity of land use by humans increases, natural vegetative cover is replaced by less complex vegetative systems, such as selectively logged conifer stands, lawns and flower beds, and total area of vegetation is reduced. These simplified and reduced vegetative cover systems have reduced ground water infiltration, increased surface runoff, and decreased runoff accumulation times. Wildlife habitat diversity is drastically reduced, as is the number of species present in the habitat.
The support systems of intensive land use replace natural land cover with hard surfaced roads, parking areas, sidewalks and roofs. These impervious land covers concentrate runoff in hydrologically efficient systems and reduce the amount of land cover available for ground water recharge. The hydrologically efficient systems alter the natural flows of both surface and ground waters in a watershed, drying up former wet areas, and inundating former dry areas.
Complexity of wildlife habitat is in direct correlation to the complexity of vegetative cover. Complex land covers support a wide variety of native species of animals, insects, and birds. Simple systems of land cover support only a narrow variety of animals, insects, and birds, many of which are introduced to the area. For example, opossums, starlings, rock doves and English sparrows seem to dominate many heavily urbanized areas. Simplified areas of vegetative cover, such as lawns, are maintained as biologically static communities.
San Juan County's land cover is dominated by forests, which protect the shallow soils and provide abundant habitat for many species. Almost seventy percent of the county is covered by forest lands consisting mostly of conifers such as Douglas fir, Western hemlock, and Western red cedar. Big-leaf maple and Red alder are also common to the area. Most of the remaining landcover in the county is grasslands, largely used as agricultural land for hay or pasture, but with some naturally occurring open prairie areas. The remainder of the county is covered by scrub/shrub plant communities such as willow, Nootka rose, bitter cherry, and ocean spray.
From the 1800s to the 1930s the entire county was logged to produce lumber, fuel for lime kilns and steam-powered boats, or to clear land for agriculture. However, a large portion of the county's landcover has regenerated into second-growth woodlands. The county contains significant natural areas of great diversity and beauty. A discussion of the value of landcover as habitat is in the subsection on Terrestrial Habitat in this Chapter.
Land cover is a condition that changes over time and is best measured by examination of aerial photographs, topographic maps, and analysis of satellite imagery.
Land use does not have a direct correlation to land cover. Areas of permitted land use are best measured by using official county land use planning maps and plats. Designated land use categories under San Juan County's Comprehensive Land Use Plan include: Agricultural Resource Lands, Rural Farm Forest, Forest Resource Lands, Rural Commercial Lands, Rural Industrial Lands, Rural Residential, Special Districts, Conservancy and Natural areas, including public lands. See the following section for a description of these designations.
Special tax categories (current use taxation) have a higher correlation to land cover than the land uses listed above. These include Designated Forest and Farm Lands and Open Space designations, such as Open Space Agriculture, Timber, Recreational, and Open-Open Space. These tax incentive programs reward landowners who maintain their property as resource land, under the state Open Space Taxation Act of 1970. This Act supports the concept that it is in the best interest of the State to maintain, preserve, and conserve adequate open space lands for the production of food and forest crops and the enjoyment of natural resources and scenic beauty.
Land
Use
Land use, from the watershed perspective,
is the modification of natural vegetation cover and permanent
alteration and removal of land cover for development, and the
various resulting activities that can impact water quality and
quantity. Clearing, grading, constructing ditches and impervious
surfaces, such as roofs, roadways and even lawns , change the
flow of surface water and introduce sediment into wetlands, lakes
and streams.
Land use activities affect watershed conditions by covering the ground with impervious and semi-pervious surfaces and introducing pollutants into surface water through home and business practices, such as the use of toxic substances for construction, equipment maintenance, and fuels. The islands have 210 miles of paved county roads (and 71 miles of dirt roads) covering a total of 1,295 acres, or more than 1 percent of the land area of the county. Additional paved surfaces include areas in the Town of Friday Harbor, airports on San Juan, Orcas and Lopez, and parking areas in Roche Harbor, Eastsound, Rosario, and Lopez Village. Gas stations, car washes, boat repair yards, golf courses, animal enclosures and septic waste disposal systems are some of the land uses that generate pollutants. Existing residential development in San Juan County tends to be concentrated along shorelines and in upland areas with views. This creates a potential for pollution where runoff is high and nearshore environments are directly impacted.
The San Juan County Comprehensive Plan establishes four principal land use classes for the County. Each class permits a different level of activity. The four general classes are Activity Centers, Rural Lands, Resource Lands, and Special Districts; the individual land use categories within the classes are referred to as "Districts." These classes have been developed based on: natural systems and land capability; existing land use patterns; the needs and expressed desires of the community; and coordination with the Shoreline Management Act and the County Shoreline Master Program.
1. Activity Centers. The purpose of this land-use class is to provide centers of activity in a concentrated development pattern which offer diverse employment opportunities; a variety of residential densities and housing types; and general commercial, general industrial, institutional, recreational, and community uses. This land-use class includes five categories or "districts" a. Friday Harbor Urban Growth Area District (UGA), b. Village District (V): Commercial (VC), Industrial (VI), Residential (VR); c. Hamlet District (H): Commercial (HC), Industrial (HI), Residential (HR); d. Island Center District (IC); and, e. Master Planned Resort District (MPR)
2. Rural Lands. Rural lands are intended to retain the pastoral, forested, and natural landscape qualities of the islands while providing people with choices of living environments at lower densities or use intensities than those in Activity Centers. This land-use class includes five categories or "districts": a. Rural General Use (RGU); b. Rural Residential (RR); c. Rural Farm Forest (RFF); d. Rural Industrial (RI); and, e. Rural Commercial (RC)
3. Resource Lands. The purpose of this land-use class is to recognize and protect the physical conditions and characteristics of agricultural and forest resource lands which are conducive to the use of such lands for long-term commercial production. This land-use class includes three categories or "districts": a. Agricultural Resource Lands (AG); b. Forest Resource Lands (FOR); and, c. Mineral Resource Lands (MRL) Overlay District
4. Special Districts. The purpose of this land-use class is to protect, conserve, and manage existing natural conditions, resources, and valuable historic, cultural, educational, or scientific research areas and to preserve indigenous plant and animal species and ecosystems in a natural state for the benefit of existing and future generations without precluding compatible human uses. This land use class includes two categories or "districts": a. Conservancy Lands (C); and, b. Natural Lands (N)
The climate of the San Juan Islands is influenced by the Olympic Mountains and Vancouver Island, situated southwest and west northwest of the San Juan Islands, which create a "rain shadow" effect producing less rainfall in the San Juans than the rest of northern Puget Sound.
Precipitation at sea lvel increases from south to north in the islands as the rainshadow influence dissipates. For example, the average annual precipitation at the south end of Lopez Island is 19 inches, while the northern portion of Orcas Island receives 30 inches average annual precipitation (EES 1990). Precipitation also increases with higher elevation producing a maximum average annual precipitation of 45 inches on Mount Constitution. Snowfall is not a significant factor in the San Juan Islands.
Rainfall can also vary widely from the averages shown in figure 2-2. Figure 2-3 shows the mean annual precipitation recorded at the Olga weather station from 1890 until 1997. The record shows that annual rainfall has varied at Olga between 15 and 38 inches between 1890 and 1997.
The maritime air surrounding the islands moderates the climate. Summers are relatively short, cool and dry, and winters are mild and moderately dry when compared to other portions of northern Puget Sound. The average high temperature in summer is 65 F, and the average low in winter is 40 F. Winter temperatures are usually mild, except when cold, arctic air funnels down the Fraser River Valley from Canada and drastically lowers temperatures. Winds may also have a drying effect, pulling moisture from vegetation and surface water, and heightening the impact of low rainfall periods.
Two distinct types of geologic landforms occur in the San Juans. The first consists of bedrock domes thinly covered with late Quaternary (glacial) sediments commonly found on San Juan, Shaw, and Cypress (which is in Skagit County). The second type, found on Lopez, Waldron, and Decatur, is composed of bedrock buried beneath sediments more than 300 feet thick in places. However, neither formation is exclusive to any single island. Portions of Orcas, Lopez, and Waldron have surface exposures of bedrock, and parts of Orcas and San Juan have thick glacial deposits. (White 1994)
Figure 2-4. Water Supply Bulletin No. 46, 1975, Russell et al. Quaternary areas are covered with glacial deposits. Pre-quaternary are exposed bedrock.
Bedrock Geology (Pre-Quaternary)
Bedrock geology dominates the
San Juan County landscape. Surface elevations range from sea
level to 2,454 feet at the summit of Mt. Constitution on Orcas
Island. The highest point on San Juan Island is Mt. Dallas (1,036
feet); on Lopez Island it is Lopez Hill (535 feet).
Prior to glaciation, this region of the coastline was augmented by small micro-continents traveling eastward on the Juan de Fuca plate. As these landmasses impacted the main N. American continent, they were squished, squeezed and "accreted" onto the coastline. The resulting structural geology is a complex combination of overlapping thrust faults along tectonic lenses and plates (Brandon, et al 1988). These thrust systems include Paleozoic volcanic arc rocks, Mesozoic pillow basalts, limestones, cherts, high-pressure metamorphics and clastics.
Groundwater is stored in the fractures and joints of this variegated assortment of bedrock. The complexity mentioned above makes it difficult to predict the capacity and extent of groundwater resources. However, it is safe to say that due to the structural complexity and accretionary nature of the local bedrock, there are no pathways along which groundwater could travel from the mainland.
Glacial History (Quaternary)
Repeated glaciations during
the last ice age shaped the bedrock and developed the rugged
landscape of the islands. The region was scoured by a blanket
of ice as much as a mile thick which carved out marine channels,
creating the scenic beauty for which San Juan county is world
renowned.
As the glaciers advanced from north to
south they created numerous bays and
waterways including San Juan Channel, West Sound, East Sound
and Lopez Sound. Higher elevations of bedrock were carved, scraped,
and rounded. When the glaciers began melting the resulting debris
was left behind, blanketing low-lying areas with unconsolidated
glacial deposits of clay, silt, sand, gravel, and boulders.
In the San Juans, glacial and interglacial deposits are relatively thin when compared to other areas in Puget Sound where this type of deposition may be several thousand feet thick. Contour maps of sediment thickness generated from county well logs by White (1994) show most of the San Juans to have less than 20 feet of sediment cover (see Figure 2-5.). This thickness, compared to the Quaternary sediment layers in other parts of the Puget Lowland, is miniscule, and reflects the role that the bedrock elevations played in the glacial history of the islands. Glacial sediment distribution in the county varies greatly, with large pockets scattered at random in low-lying areas and little or no sediment found elsewhere. The two largest concentrations of sediment are located on Lopez and Orcas, where sections extend below sea level.
Hydrology
Over eleven thousand years
ago, the final melting of the glaciers supercharged this area
with groundwater. All available underground spaces were filled
as meltwater percolated as deeply as possible into cracks, pores,
and pockets within the bedrock. Today all of the "resupply"
or "recharge" of this groundwater comes from local
rainfall. San Juan County has no rivers and no snow pack upon
which to rely for fresh water.
cause the San Juans are so heavily dependent on rainfall to supply
domestic needs and maintain physical and biological functions,
it is important to understand how the hydrologic cycle works
in the islands.
Hydrology is the study of the character, distribution, movement and effects of the earth's water. The conditions of climate, topography, geology, soils and vegetation are interacting elements in the hydrologic cycle.
There is a common misconception in the county that fresh groundwater comes from Mt. Baker and the Cascades. This is not possible due to the structural complexity previously mentioned in the Bedrock Geology section. As well, the hydraulic head of a well is directly proportional to the elevation of the source of the groundwater. This relationship holds true no matter how far the groundwater travels from its original source. Were groundwater to originate in the mountains of the mainland, the hydraulic head of such wells would be legendary (see Figure 2-6).
Under natural conditions, precipitation either runs off the land into larger bodies of water (runoff), is used by plants and evaporates into the atmosphere (evapotranspiration), or enters ground water and is stored (recharge). All of these components influence the yield and distribution of water within a watershed.
Runoff
The amount of runoff varies
depending on slope gradient, depth of soil, type and condition
of vegetation, and precipitation. The higher the amount of runoff,
the higher the potential for erosion and subsequent nonpoint
pollution due to sedimentation.
Runoff estimates for an undeveloped landscape indicate that annual runoff at sea level varies from a low of 3 inches to a high of over 8 inches proceeding from south to north through the islands. Runoff also increases with increasing precipitation at higher elevations, up to 13 inches on Mount Constitution.
Runoff throughout the county is low for
Western Washington, due to limited rainfall, small catchment
areas, and coarse, porous glacial sediment over bedrock. However,
runoff is high proportionally, due to the presence of bedrock
and impervious soil layers. Runoff occurs chiefly from December
through March when soils are saturated and rainfall is heaviest.
Runoff estimates developed using the runoff modeling program3
indicate that 28 percent of average annual precipitation is not
captured and becomes runoff. This amount can vary from 11 percent
to 45 percent depending on the impact of evapotranspiration combined
with variations in rainfall (Russell 1975). San Juan Island's
False Bay watershed has the greatest volume of runoff for any
basin in the county with 3,154 acre-feet per year. The next largest
volume of runoff is for the Crow Valley basin, with 2,276 acre-feet.
The largest drainage on Lopez drains to Davis Bay with a volume
of 743 acre-feet (EES 1990).
Evaporation and transpiration
Evaporation and transpiration,
or evapotranspiration, is water cycled back to the atmosphere
from surface waters, soils and plant surfaces. In the San Juan
Islands, evapotranspiration is the most important water loss
annually. Although EES, in the Water Resource Assessment Technical
Report, estimated that 42 percent to 49 percent of annual precipitation
is lost to evapotranspiration, these numbers are generalized
and individual basins will vary, depending on landcover and topography.
For instance, Dietrich (1975) reported that 67 percent of annual
precipitation at Olga returns to the atmosphere through this
process; and in the Town of Friday Harbor's Trout Lake watershed,
which is steep and forested, evapotranspiration is estimated
to intercept 74 percent of the water from annual precipitation
(Town of Friday Harbor, 1999). Evapotranspiration is greatest
during the summer months, when precipitation is minimal and plants
are actively respiring. In an average year in the San Juans,
actual evapotranspiration is greater than precipitation from
mid-April through September, causing water to be depleted from
the soil.
Groundwater recharge
Wells in San Juan County are
generally completed in and produce from two major aquifer types:
glacial/interglacial aquifers and bedrock aquifers. Aquifers
are geologic zones where groundwater is found and can be extracted.
Large, productive glacial sand and gravel aquifers exist on Lopez
Island and northern Orcas. However, most wells in the county
obtain water from bedrock aquifers which are less productive.
Generally, groundwater flows radially outward from the centers
of the islands toward the shorelines. Because of a high ratio
of shoreline length to land area in the San Juans there is an
appreciable flow of groundwater seaward.
Evapotranspiration and runoff affect groundwater recharge. Using Detrich's figures for Olga as an example: the average annual rainfall is 29" and 67 percent, or 19.4", is lost to evapotranspiration, another 6.49" is lost to runoff, and the remaining 3.1" (10 percent) is available for recharge. In the Water Resource Assessment Technical Report (EES 1990), recharge estimates varied from as low as .1" (less than 1 percent) for southern Lopez during a drought year, to a maximum of 13.6" (30 percent) in an average year for the largest drainage on Orcas.
Actual infiltration of precipitation into groundwater is determined by soil character, gradient and runoff conditions. These conditions include the volume and timing of the water at the surface; infiltration capacity of the soil; condition, type and amount of vegetative cover; porosity of the underlying geology; aquifer characteristics (such as storage capacity); and topography. The complexity of these factors requires that calculations of recharge potential be developed using detailed, site-specific data.
Bedrock Aquifers
Bedrock aquifers are a network
of interconnected bedrock fractures and fracture zones (see Figure
2-8). A majority of the wells in San Juan County are in aquifers
located in fracture zones in the underlying bedrock. Wells of
this aquifer type produce water by intersecting enough connected
bedrock fractures to cause a significant flow of water to enter
the well borehole. Bedrock aquifers provide very little filtration
of contaminants for the waters that flow through them.
Most bedrock wells have water levels within
20 to 30 feet of the surface, although the water-yielding fractures
may be much deeper (EES 1990). Whiteman (1983) cites the mean
well-bottom altitude of bedrock wells at 123 feet below sea level.
Yield for most bedrock wells is typically low, with rates between
one and 10 gallons per minute. Most bedrock wells are drilled
deeply in anticipation of intercepting additional water-yielding
fractures. However, the occurrence of water-yielding fractures
usually decreases with increasing depths and these added depths
only provide additional storage capacity from which to draw water
(Whiteman 1983).
Glacial Drift Aquifers
Glacial drift aquifers are located in outwash glacial
deposits left by retreating glaciers. Water in these aquifers
occurs in spaces between particles of sand and gravel. These
gravels and sands can act as a filter for contaminants, but are
also porous enough to allow contamination under the right conditions.
Wells drilled into glacial drift aquifers on Lopez Island generally have water levels within 10 feet of sea level, regardless of the land surface elevation. Yields for wells in glacial deposits can exceed 50 gallons per minute , however, yields in most glacial drift wells are closer to 5 to 10 gallons per minute (Whiteman, 1983; SJC Health and Community Services, 1999).
The high degree of porosity and hydraulic connection to seawater as well as depth and location make these wells highly susceptible to seawater intrusion. Seawater intrusion is the migration of seawater into a freshwater aquifer. It is usually caused by pumping water at an excessive rate from an aquifer that is hydraulically connected to the sea, or by drilling too deep and penetrating the salt water interface. Seawater intrusion is an existing problem in many sand and gravel aquifers as well as in some fractured bedrock aquifers in San Juan County.
In addition to limited rainfall recharge and aquifer storage capacity, the safe yield from many aquifers is limited by seawater intrusion. A study of San Juan County groundwater by the U.S. Geological Survey (USGS) in 1981 found that 9 percent of 279 wells sampled county-wide had evidence of seawater intrusion (Whiteman, et al. 1983). Additional work is being conducted by the USGS to further assess the capacity of the county's glacial drift and bedrock aquifers, and the extent of seawater intrusion. A report on chloride concentrations in wells on Lopez is due in spring of 2000. Data from this study indicate that 25% of the wells sampled in 1997 on Lopez are experiencing salt water intrusion and almost 50% have elevated chloride levels.
Soils
Soil is a product of the soil-forming
processes acting on material deposited or accumulated through
geologic forces. Climate and living organisms, particularly vegetation,
are the active forces in soil formation. Their effect upon the
parent material is modified by topography and the length of time
the parent material has been in place.
Soil is composed of varying sizes of mineral particles, organic matter and multiple species of living organisms. The biological, chemical and physical properties of soils are in a constant state of flux.
Many processes are taking place in the
soil. Soil acts as a filter to protect the quality of water.
Soil characteristics can influence the distribution of rainfall
as surface water runoff, ground water infiltration, and ground
water storage. The 
regulation
of water flow through soil affects the movement of soluble materials,
such as pesticides, fertilizers and toxic materials.
Soil regulates biological activities and molecular exchanges among solid, liquid and gaseous phases. This regulation affects nutrient cycling, plant growth, and decomposition of organic materials. Soil also is a physical, chemical and biological environment in which water, nutrients, and heat are exchanged with plants and animals.
Soil surveys classify soils by the limiting factors that restrict the ability of the soils to fully perform all of the processes listed above. Three principal limiting factors occur in the soils of the county, according to the USDA-Soil Conservation Service, Soil Survey of San Juan County, dated November, 1962.
The limiting characteristics in 57 percent of the soils in San Juan County are the shallowness of the rooting zone, stones in the soil profile and low moisture-holding capacity in the root zone. Many of the soils in this limitation class are less than 30 inches in depth and sit atop a cemented glacial till layer (hardpan) that restricts the downward flow of water. The soils that are deeper than 30 inches are located above coarse layers of sand and gravel that allow water to drain through the soil very rapidly.
Excessive water is the dominant hazard or limitation affecting the use of 23 percent of the soils in the San Juan soil survey. This hazard/limitation includes poor soil drainage, soil wetness and a high water table.
Susceptibility to erosion is the dominant hazard or limiting factor in 19 percent of the soils in the County. The majority of the soils and soil complexes in this classification have slopes in excess of 30 percent and were mapped as rock areas or soil and rock complexes in the soil survey.
Soil erosion is a natural process that can be accelerated by human action. Removal of protective vegetative cover from topsoil exposes the soil to the impacts of rainfall. This impact can cause individual soil particles to break loose and be carried downslope. This process causes a loss in soil nutrients and often leaves behind an environment that is less favorable for plant growth. Water eroded soil particles become sediment that moves offsite, damaging fish and marine habitats, decreasing infiltration, and degrading water quality. Increased surface water runoff from human actions can also accelerate soil erosion.
Human actions can degrade soil capability by compacting the air spaces in a soil. Compaction occurs primarily when heavy equipment or farm animals exert pressure on wet soils. The effects of soil compaction include restricted plant growth, increased soil moisture, decreased soil temperatures, decreased water infiltration and increased surface water runoff. The soils of San Juan County are particularly susceptible to damage by compaction because of their thinness and relatively high clay content.
Wetlands, lakes and ponds provide water
storage in the landscape. The number and size of lakes, ponds
and wetlands in a watershed are measures of its water storage
capacity. Wetlands, lakes, ponds and streams also serve an important
function in maintaining good water quality. Wetlands provide
a beneficial use of water by providing wildlife habitat and aesthetic
enjoyment. As land is developed and used, these important qualities
storage, purification and habitat -- are disrupted.
Wetlands
Wetlands benefit the hydrologic function of a watershed.
Wetlands store water, purify water, filter runoff, abate flooding
and decrease erosion. They act as ground water recharge and discharge
sites. In general, the higher the proportion of acreage in wetlands
in a watershed, the greater the functional capacity of that watershed
to store, purify and filter water, and to capture sediments.
In the watersheds studied in this report, identified fresh water
wetlands comprise as little as one percent to as much as 12 percent
of the total watershed area.
Wetlands are generally identified as areas where excess water is present during part of the growing season (either soil saturation or inundation), a wetland vegetation community is evident, and soils show evidence of periodic saturation or flooding.
The maps in this report show the general location and extent of wetlands from the National Wetlands Inventory (U.S. Department of the Interior) and the San Juan County Wetlands Inventory (Sheldon, 1993) . These wetland boundaries were derived from analysis of aerial photos and some field reconnaissance. Delineations, which define the actual boundaries of a wetland based on field surveys of soil conditions, are not included in these maps. Not all wetlands were identified by these two surveys. Many known wetlands are not shown on the maps, particularly small wetlands, forested wetlands and some estuarine (where fresh and marine waters meet) wetlands. Many of the wetlands found in San Juan County are small -- less than 50 ft2 -- and are unregulated under state and county laws. Under federal law, wetlands are more stringently protected. For example, a wetland less than 50 ft2 that contains habitat for listed species or significant cultural resources is protected with no limitation to size.
Freshwater wetlands in the County mostly occur in bedrock depressions or in depressions underlain by glacial till, deposited and compacted by glaciers. The largest freshwater wetland systems in the county are found in the False Bay and Friday Harbor watersheds on San Juan Island.
Information on present or historic wetland loss for San Juan County is not available. Data gathered for the National Wetlands Inventory (NWI) suggests that the Puget Lowland (which includes San Juan County) lost between 30 and 70 percent of its wetlands up to 1980, when wetland data was first collected. Federal wetlands protection legislation was started in 1972, under the Clean Water Act.
Alterations to wetlands include ditching and draining, mowing or grazing of wet meadows, dredging for ponds, and filling for roads and building sites. Some wetlands in the County have been converted to ponds and to pasture for grazing and hay production. Although they have lost some of their use as wildlife habitat, these areas remain wetlands and, depending on the degree of alteration and management practices, can perform important wetland functions, such as storage and filtration.
There are a variety of laws and regulations at the federal, state, and county level that affect construction and other activities in wetlands and adjacent areas. Some of these regulations only apply to certain wetlands or certain activities in wetlands, and the provisions of these laws can vary. In San Juan County, wetland regulations treat wetlands differently depending upon their location, and how they score in a wetland rating/classification system. Case-by-case review is needed for individual projects that occur in or near wetlands, and applicants are advised to contact the proper authority prior to project development. The primary means for protecting water quality and maintaining beneficial uses in wetlands in the State of Washington is through the implementation of water quality standards when issuing development permits. The beneficial uses of wetlands can be protected and maintained through permit requirements tied to the Clean Water Act. These federal regulations apply even to wetlands not covered in county regulations.
Lakes and Ponds
Lakes, reservoirs and ponds
occur throughout the islands and are important sources of water
for wildlife, domestic use, irrigation, stock watering, fishing
and recreation. Lakes supply much of the domestic water used
on San Juan and Orcas islands. Trout Lake and Briggs Pond supply
domestic water for the Town of Friday Harbor and Roche Harbor,
respectively. Rosario uses Cascade Lake; the Olga and Doe Bay
water systems depend on Mountain Lake; and Eastsound uses Purdue
Reservoir as a back-up for well water sources.
Orcas Island, with its rugged, rocky terrain, has the largest lakes in the county. Lopez Island, due to gentle topography, lack of rainfall and porous, glacial sediment overlay, has the least amount of surface water impoundment.
|
|
|
|
Lake Volume (acre-feet) |
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
Streams
Watersheds in the islands are
usually less than five square miles in size, with streams that
flow between late November-December and early May. There are
two perennial streams of significant size on Orcas Island: Cold
and Cascade creeks (Whiteman 1983). Cold Creek is fed by a large
spring, and Cascade Creek by Mountain Lake. On San Juan Island
two streams run all year. These streams are San Juan Valley Creek,
which starts at Trout Lake on Mt. Dallas and joins up with the
drainage system for the wetlands of the False Bay watershed,
and a small creek that begins at the back of Mt. Cady and drains
into Garrison Bay.
Because most streams in the San Juans are seasonal, they have limited value for salmon production. Many of the county's streams have been altered by ditching or diversion, and have been affected by the extensive logging that took place in the county at the turn of the century. However, long-time residents report that most of the larger streams supported fish runs in the recent past. Some of these streams include: the creek running from Trout Lake through San Juan Valley to False Bay and the creek running into Garrison Bay on San Juan Island; the creek from Hummel Lake to Swifts Bay on Lopez; and the creek that drains Crow Valley -- which is reported to have been a perennial stream prior to the logging of Turtleback Mountain in the 1920's and 1930's. Cascade Creek on Orcas currently supports anadromous fish in its upper reaches.
The state has classified streams into five designations (222-16 WAC, State Forest Practice Regulations), roughly described as follows. Class 1 type waters are designated as "shorelines of the state," but not including their related wetlands. Class 2 type streams are those used as a major public source of drinking water, or used by a substantial number of anadromous or resident game fish for spawning, rearing or migration, or streams having more than 20 feet in width and less than a four percent grade. Class 3 type streams are those serving as a smaller public water source, also habitat for fish, with a width of five feet or greater and a grade of less than 12 percent. Class 4 and 5 type streams are significant for the protection of downstream, Class 1 3 waters.
In 1999, according to the Forest Practices division of the Washington State Department of Natural Resources, emergency rules governing Class 4 and 5 streams are currently in effect. These rules require that all Class 4 and 5 waters that are two feet or wider between ordinary high water marks, and have a gradient of less than 16 percent be treated as Class 3 streams. These emergency rules apply to waters that have not been evaluated to determine the presence or absence of fish.
Figure 2-8. (Watershed Ranking Report 1988)
Habitat is the term used to describe physical and biological conditions of the land that support the feeding, breeding, nesting and rearing of young for wildlife. San Juan County has three major types of habitat: freshwater, terrestrial (uplands), and marine.
Over 291 species of birds are recorded in the San Juan Archipelago, and it is one of the most important regional locations for breeding, migrating and wintering of seabirds. The shorelines of the county support the largest bald eagle population in the lower United States and host a rare Golden eagle population. Other birds of distinction found in the county include loons, vultures, herons, peregrine falcon, merlin, purple martin, trumpeter swans, Cooper's hawk and the marbled murrelet (Lewis & Sharpe 1987).
Twelve species of marine mammals, 24 different terrestrial mammal species, including river otter, mink, and Columbia black-tailed deer, and hundreds of species of marine invertebrates and fish are found in San Juan County. Small mammals include the white-footed deer mouse, Townsend's vole and vagrant shrew. Beavers are found in some parts of Orcas Island and have been present on San Juan and Lopez in the past. Amphibians and reptiles that may be observed in the San Juans are the rough-skinned newt, red-legged frog, Western toad and Northern alligator lizard. (Vernon 1996).
Species found in San Juan County listed by state and federal agencies for protection under the federal Endangered Species Act. These animals are considered priority species due to their food value, game status or rarity by the Washington State Department of Fish and Wildlife (WDFW). Priority Habitats are designated by WDFW in areas where species of concern are found. Species of Concern or Priority Species in Washington include all Endangered, Threatened, Sensitive, and Candidate species. Priority species also include Federal, Endangered, Threatened, and Candidate fish stocks. The Washington Natural Heritage Program (WNHP) develops and recommends strategies for protection of the native ecosystems and species most threatened in Washington State.
Wetland Habitat
Both fresh- and salt-water
wetlands provide important habitat functions in San Juan County.
Wildlife associated with wetland ecosystems includes resident
and transient
mammals, birds, reptiles, amphibians and the many insects that
provide food and essential biologic functions in the watershed.
Many wildlife species, such as, beaver, frogs and salamanders
depend on wetlands for their survival. Other upland wildlife
species depend on wetlands for essential aspects of their life
support. Different wetland types: open water, scrub/shrub, or
forested, support a diversity of wildlife. (DOE 1996) Freshwater
wetlands support many bird species in the county, for forage,
drinking and bathing, and nesting. Some seabirds, such as grebes,
live on salt water but nest in freshwater areas. (Lewis and Sharpe
1987)
Common species found in freshwater wetlands and bogs in San Juan County are the tree Pacific willow and the shrubs hardhack and swamp gooseberry. Speedwells and herbs most always found in wetlands and long the edges of streams and lakes, as well as buttercups field mint, and small bedstraw. Alder and salmon berry often dominate in wet areas, generally where disturbances have occurred. Slough sedge is the most abundant sedge occurring in poorly drained areas as well as dominating many wet meadow pasture lands. Indian pond-lily is an important aquatic wetland species and a critical component of the ecology of the county's wetlands, with large flat leaves which lay on the water surface and serve as feeding and hiding sites.
Freshwater wetlands and marshes also support several of the endangered plant species that are found in San Juan County, including swamp sandwort, rush aster, water lobelia, few-flowered sedge, and blunt-leafed pondweed. Some of these valuable marsh areas include: Otter's Den Marsh on Orcas, and Panorama Hill Marsh, Mt. Finlayson Marsh, and Three Meadows Marsh on San Juan (The Nature Conservancy 1975). Spruce bogs are another important type of freshwater wetland, which are rare in the county. Point Colville on Lopez contains a spruce bog, which is hidden in the dense old-growth forest, dominated by sedges, rushes, Sitka spruce, grand fir and red alder. The rare grape fern is found here, also.
Saltwater marshes and brackish lagoons are found at the edge of the shoreline, generally associated with accretion shoreforms. This combination of eroding shoreline, mud flats, and the mixing of fresh and salt water support unique plant life that is essential to the ecology of eelgrass beds and the rich microorganism communities that sustain marine life through a complex food chain. Salt marshes are dominated by salt grass and pickleweed. Examples of these important biologic areas include: Nelson Bay on Henry Island, White Point and Westscott Bay on San Juan, and Mud Bay on Lopez.
Terrestrial Habitat
San Juan County's upland habitat
is characterized by rocky hills of exposed bedrock thinly covered
by soil. Near-drought conditions during the summer months combined
with these soil conditions have created arid sites with plant
communities unusual for the Puget Sound area. Forest lands are
the predominant land cover in the county, with second-growth
coniferous trees taking hold where water is available. In these
wooded areas birds such as the Cooper's Hawk, Pileated Woodpecker,
and Red Crossbill thrive.
Extensive grassy prairies and grassy balds,
and open savannah-like woodlands are common on southern and western
exposures. Over 800 kinds of vascular plants have been cataloged
in the San Juan Islands, two-thirds of which are native (Lewis
and Sharpe; 1987, Atkinson and Sharpe, 1985). Large grassland
complexes are evident on Mount Constitution and the southern
slopes of the Turtleback Range on Orcas Island, the west side
of San Juan Island, Iceberg Point on Lopez Island, Speiden Island
and Yellow Island. Relatively undisturbed prairies (as indicated
by the dominance of native plants) are identified by the Washington
Department of Fish and Wildlife as a priority habitat. Such areas
are considered to have high species diversity as well as limited
and declining availability.
Open, rocky outcrops with rocky knolls and steep slopes are a
common feature, and plant communities in this terrain are survivors
of extreme conditions. Lichens and mosses survive on the bare
rock and grasses and herbs are common in pockets that retain
some soil and moisture. Garry oak, Rocky Mountain juniper and
Pacific madrona are able to anchor in the thin soil in these
areas (Atkinson and Sharpe 1985).
San Juan County forests are much drier than those of the mainland
Puget lowland. Many forested areas are lacking in underbrush
and have an open canopy and park-like appearance. Douglas fir
dominates in most areas but varies substantially in growth habit
depending on environmental conditions. Forest character in the
San Juan Islands changes from site to site as a result of wind,
sunlight, soil type and depth, topography and moisture, as well
as human management.
Old growth (more than 200 years) and mature forests (80 to 200
years) of any kind are identified as priority habitat areas by
WDFW. This designation is largely due to their declining availability,
due to selective harvest, and high value for plant and animal
diversity.
Where forests are disturbed by logging, fire, or clearing of
any kind, pioneer native species such as red alder, bitter cherry,
bracken, Nootka rose, ocean spray, stinging nettle and the red-flowering
currant, as well as non-native species, including weeds, may
move in to fill the openings.
Dry sites (Xeric)
In dry sites with poor soils,
an open transitional type of forest is found, often on very steep
rocky slopes adjacent to saltwater. Trees in these areas include
Garry oak, Pacific madrona, and occasional lodgepole pine and
Rocky Mountain juniper. Other species that survive in these conditions
include ocean spray, serviceberry, snowberry and tall Oregon
grape.
Pure or mixed stands of oak or oak savanna larger than one acre
are considered state priority habitats as they have significantly
declined in extent and have high wildlife and plant diversity.
Open grassland and grass balds, as described above, are also
dry site communities. These areas are dominated by grasses that
can survive dry soil conditions such as Idaho fescue, brome,
and velvet grass; and wildflowers such as Hooker's onion, nodding
onion, harvest brodiaea, thrift, camas, death camas, and chocolate
lily.
Moist sites (Mesic)
In intermediate moisture conditions
between dry and moist woodland, Douglas fir is more dominant
and denser although transitional species occur. This forest habitat
type is found on gentler slopes, with greater sun and wind protection.
Soils are deeper and heavier than in the open transitional forest
and have a thicker duff layer.
Typical shrubs are salal, low Oregon grape and little wild rose
(Rosa gymnocarpa). In some areas soopolallie, rare west
of the Cascades, is abundant. Often heavy moss beds interspersed
with herbs are also present.
On north-facing slopes and areas where cool, humid and low wind
conditions prevail, Douglas fir declines slightly in dominance
among tree species and western hemlock and western red cedar,
which grows in shade, increases. Big-leaf maple is evident. Red
alder and western red cedar are found in poorly drained sites,
the former requiring full sun and the latter needing shade.
Sword fern, western foam flower and fringecup are found in moister
forests. On poorly drained sites, thickets of salmonberry are
prevalent.
As this forest type ages, western hemlock dominates as it is
able to regenerate under a closed canopy. Much of Mount Constitution
is an example of this forest type where the understory is often
virtually bare except for fall mushrooms, coralroots and saprophytic
heaths in the spring and summer. Another example of this forest
type is near Point Colville on Lopez Island.
Priority site characteristics
Pure or mixed stands of aspen
of more than two acres are also considered a priority habitat.
Such stands are found at Crescent Beach on Orcas Island and in
the Swift's Bay watershed on Lopez. Cliffs more than 25 feet
high are considered to be significant for wildlife breeding.
Other upland habitat of importance includes the presence of snags
in numbers and sizes of exceptional value to wildlife due to
their overall scarcity or location in a particular landscape.
Examples include large, sturdy snags adjacent to open water and
remnant snags in highly developed or urbanized settings.
San Juan County's marine habitat is one of the most unique in the nation. Located at a juncture of the Straits of Juan de Fuca and the Straits of Georgia, the archipelago forms a complex tidal region where many different shoreforms offer feeding, spawning, and resting areas for diverse resident and migrating marine life. The San Juans support a vast number of baitfish, salmon, marine birds, and marine mammals, including porpoise and several species of whales. Over 100 orca whale live in the archipelago, as well as the largest octopus in the world (O. dofleini) which thrives on the cold, oxygen-rich water. (Lewis, Kozloff)
The watersheds of San Juan County all feed directly to salt water. Although this report is focused on larger watersheds that have been defined by the bays they drain to, all of the shoreline of the county is affected by upland and shoreline activities. Much of the county's rocky shoreline is drained by micro-watersheds of only a few acres.
Rocky shores
The rocky shores of the San
Juan archipelago vary greatly due to differences in geology,
topography, and their situation relative to the prevailing climate,
currents and wave action (Kozloff, 1973). Unlike lower Puget
Sound, where wave action is negligible, these rocky shores are
subject to strong wave action during storms and many animals
and seaweeds thrive in this turbulent intertidal zone. Varying
rock formations provide barriers that create protected ledges,
crevices and tide pools offering a rocky intertidal zone where
an abundance of marine organisms thrives.
Kelp reefs along these shorelines are highly productive and the strong tidal currents provide nutrient rich waters that support many marine organisms and feeding areas for birds. Offshore islets and rocks are used by large numbers of harbor seals and a large percentage of the seabirds of the state breed and roost here (Lewis 1988).
Sandy beaches
The sandy, gravelly beaches
of the San Juans, with their breaking waves and shifting sands,
do not offer extensive intertidal habitat, but the associated
accretion shoreforms and marshes provide abundant seabird nesting
and feeding areas. These beaches also provide extremely valuable
offshore marine habitat, including eelgrass beds, where smelt
and sand lance breed, providing prey for larger fish, such as
salmon, and birds.
Protected bays
The quiet bays of the San Juans
are generally protected from wave action and provide a rich intertidal
zone where fresh and marine waters mix. The character of the
substrate in bays ranges from fine sand to real mud and hard-packed
clay, with gravel and rocks scattered about. This allows for
a diverse fauna and flora (Kozloff 1973). The sandy substrate
provides shallow pools at low tide which may have extensive colonies
of eelgrass. Eelgrass supports a wealth of marine organisms,
including important spawning ground for baitfish, such as herring.
Mud and muddy sand support large populations of astonishing diversity,
from the microscopic level up to the bivalves and crustaceans
so popular for commercial and recreational harvesting. In San
Juan County the accessibility and variety of these bays and the
outstanding populations of marine organisms provide exceptional
opportunities for scientific research. Researchers and students
have produced hundreds of studies based on local marine flora
and fauna and courses in marine botany, marine phycology, marine
zoology, advanced invertebrate zoology, and comparative invertebrate
embryology depend on local sites for research (Strathmann, pers.
comm. 1998).
|
Homepage | Part 1 Contents | Part 2 Contents | Next |