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The Channeled Scablands of Eastern Washington

Spokane, Washington


OVERVIEW

The Channeled Scablands of Eastern Washington refer to a geological feature that is found within a geographical area. It is not a tight, homogeneous biozone. Much of it has been altered by agriculture and other types of habitat occur within its boundaries. Consequently, certain bird species are present according to a distribution unrelated to the specifics of the title.

Lakes, sloughs, creek bottoms, fields, small town parks, and conifer groves attract species which have no affinities with the scablands but are very much part of its landscape. It is also interesting to note, however, that many of these species are represented under conditions which are directly influenced by the scabland configuration. Thrushes, warblers, mountain finches and others are hardly birds of arid open country and yet they offer spectacular concentrations in fall and spring and closer observation possibilities than they do in their normal habitat. Isolated groves of dense trees seem to draw vagrants weary of the vastness of the region, and several rare species have been recorded in such locations.

That vastness, although not the exclusive habitat of wintering raptors or passerines, is certainly very well suited to receive them. They are found in larger numbers in the scablands than they are in neighboring hills or more populated, and more densely farmed areas.

Therefore, in the context of this publication it was logical to include all the bird species present in the channeled scablands of Eastern Washington.

GEOLOGICAL HISTORY

The Channeled Scablands of Eastern Washington form a distinctive and unique landcape, exhibiting som e of the most dramatic erosional features on the planet. They are characterized by the deeply scoured volcanic rock which is found on and near the surface of a major part of the Columbia Plateau. Generally the scablands to the east.

The lava field which is the bedrock for the Channeled Scablands is tilted from Spokane in the northeast to lower elevations near the Tri-Cities in the southwest. The differences in elevation and Cascade mountain-dominated weather patterns account for most of the contrast in climate and vegetation over the area, with the northeast edge being coolest and wettest. Annual precipitaion in this area averages about 18 inches, while the driest areas in the southwestern basin average about 7 inches. Most of the natural vegetatin in the scablands is recognized as part of the shrub-steppe ecosystem, dominated by a sage brush perennial grass community, but including many other species. In the east and the north are forest-steppe areas...here, ponderosa pine is the dominant tree. Scattered throughout the Channeled Scablands along the old flood channels, one can find potholes, lakes, and intermittent streams; many with riparian and wetland vegetation.

The geologic history of the Channeled Scablands wasn't determined until the 1920s when J. Harlen Bretz made a comprehensive study of the region. He recognized that the large scale of many of the features indicated they were caused by a catastrophic event. He proposed a giant flood as the catastrophe, and over time this theory came to be gernerally accepted. Acutally, the scablands were carved by a series of floods, but it appears that the last one was the largest and destroyed most of the evidence of the earlier ones. These floods are thoght to have occurred 12,000 to 20,000 years ago during and following the Ice Age.

The largest series of flood events are known as the Spokane Floods. They are the greatest floods known to man. These events occurred when an impoundment of glacial meltwater known as Lake Missoula broke through an ice dam near the point where the Clark Fork River empties into Pend Oreille Lake. Lake Missoula had a surface area of 3,000 square miles and contained 500 cubic miles of water. Its surface was at an elevation of 4,150 feet and it was nearly 2,000 feet deep at the location of the ice dam. At present-day Missoula, the lake was 950 feet deep. When the dam broke the lake drained quickly, maybe whithin a few days. Maximum flow at the time is estimated to have been at least ten times the current combined flow of all the rivers of the world.

By the time of the Spokane Floods, the basalt sheet of the Columbia Plateau was already tilted from Spokane toward the Tri-Cities. The enormous wall of water rushed toward the southwest in three main channels: the Cheney-Palouse tract, the Crab Creek drainage and the Grand Coulee. Hundreds of smaller channels were also created. Because basalt cools into fissured columns, the floodwaters plucked off great walls of rocks, separating them along their vertical joints. In places, the waters formed giant retreating cataracts, whirlpools, and eddys which scoured and formed the existing labyrinth of large coulees, cliffs, craters and canyons known as the Channeled Scablands.

BOTANY & FEATURES

CHANNELED SCABLANDS HABITATS
The Channeled Scablands of East Central Washington are characterized by a series of biogeographical assemblages known collectively as "shrub-steppe" habitat types. According to Daubenmire (1971), there are two major subdivisions of native shrub-steppe habitat:

  1. Artemisia tridentata-Agropyron spicatum association
  2. Artemisia tripartita-Festuca Idahoensis association
The floristic differences of these large associations are a function of climatic and edaphic differences found in the region, but they do not vary significantly from a process, or ecosystem function, standpoint. They are representative of a cold desert climatic regime, and offer many ecological similarities to the sagebrush-dominated systems of the Great Basin in Southeastern Oregon, Southern Idaho and Northern Nevada.

Many endemic vertebrates show adaptation to the large expanses of open sagebrush-bunchgrass plains that would ordinarily be typical of a natural landscape in the Columbia Basin. Species such as ferruginous hawk, sage grouse, and some others which have large home ranges represent a successful exploitation of these landscape-level habitat conditions.

Within the confines of the Columbia Basin shrub-steppe are dozens of smaller habitats, representative of diverse soil, topography, miroclimatic, moisture, and other physical manifestations on the landscape. These include wetlands, herbaceous and woody riparian areas, saltgrass meadows, upland shrub garland communities, rigid sage ridges, aspen thickets, grasslands, ponderosa pine islands, rocky outcrops and cliffs, and so forth. While these smaller habitat representations only make up a small percentage of the larger shrub-steppe system, the presence of these smaller habitats adds immeasurably to the value of the remaining area in terms of diversity. The relationships of these small inclusions to the overall shrub-steppe system are only partially understood, but they are certainly important to the maintenance and sustainability of the system as a whole.

Since the Columbia Basin was first occupied by white settlers, the extent of the shrub-steppe ecosystem has diminished to but a shadow of its former existence. The Washinton Wildlife Department has calculated that only 17% of the upland natural vegetation type(s) still exists today. This decline has had a profound effect on native wildlife, and over 20 shrub-steppe species are currently listed by state or federal authority in some category of concern. Of the natural habitats remaining, many are broken into small fragments, interspersed with agriculture, highways, or vegetation conversions to monotypic grasslands. Empirical information suggests this fragmentation may be the most significant impact on continued existence of viable populations of many shrub-steppe species.


ACKNOWLEDEGMENTS

The BIRDS OF THE CHANNELED SCABLANDS OF EASTERN WASHINGTON was published as a volunteer effort in cooperation with the Department of the Interior, Bureau of Land Management.

We would like to recognize the Spokane District Manager and professional staff for their technical assistance and support. Our thanks also go to our friend, Jim Acton for sharing his vast knowledge and records with us.

It was our intention to make this booklet attractive and informative without the constraints of a purely scientific presentation.

We trust that ornithologists, amateurs and professionals, distant and local, will equally enjoy its contents and that it will make their visits to the region a more complete experience.

MARK HOUSTON, MAURICE VIAL
Members of the Washington Ornithological Society


FOR MORE INFORMATION
Allen, J.E. and M. Burns.  1986.  Cataclysms on the Columbia.  Timber Press, 
     Portland, OR.  [a detailed account of the Columbia Basin floods and the 
     history of their discovery]
     
Alt, D.D. and D.W. Hyndman.  1984.  Roadside geology of Washington.  Mountain 
     Press, Missoula, MT.  
     
Alwin, J.A.  1984. Between the mountains: a portrait of eastern Washington.  
     Northwest Panorama Publishing, Bozeman, MT.
     
Daubenmire, R.  1970.  Steppe vegetation of Washington.  Washington State 
     University.  Pullman, WA.
     
Franklin, J.F. and C.T. Dryrness.  1969.  Vegetation of Oregon and Washington. 
     USDA Forest Service Research Paper PNW-80, Pacific Northwest and Range 
     Experiment Station, Portland, OR.
     
Taylor, R.J.  1992.  Sagebrush country.  Mountain Press, Missoula, MT.  
     [primarily a wildflower guide]
     
Weis, P.L. and W.L. Newman.  1989.  The channeled scablands of eastern 
     Washington: the geologic story of the Spokane flood.  Eastern Washington 
     University Press, Cheney, WA.

This resource is based on the following source:
Houston, Mark and Maurice Vial.  1995.  Washington Spokane District, Birds 
     of the Channeled Scablands of Eastern Washington.  U.S. Department of 
     the Interior, Bureau of Land Management.  24 pages.
This resource should be cited as:
Houston, Mark and Maurice Vial.  1995.  Washington Spokane District, Birds 
    of the Channeled Scablands of Eastern Washington.  U.S. Department of 
    the Interior, Bureau of Land Management.  24 pages.  Jamestown, ND:
    Northern Prairie Wildlife Research Center Online.
    http://www.npwrc.usgs.govscabinfo.htm 
    (Version 23FEB2001).

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