Soils of the - Agriculture and Agri-Food Canada

CHEHALIS SOILS (CS)
Location and Extent : Chehalis soils are relatively uncommon in the map area . They occur mainly in the
vicinity of Norrish Creek east of Dewdney . There are about 90 ha of pure map units and 75 ha of soil complexe s
dominated by Chehalis soils . The complexes are with Elk and Isar soils .
Topography and Elevation : The topography is gently to strongly sloping or, occasionally, undulating, with
slope gradients between 2 and 10 percent . Elevations range between 15 and 40 m above sea level .
Parent Material and Texture : Chehalis soils have developed from coarse-textured alluvial fan deposits .
Surface and subsurface textures range from gravelly loamy sand to sand and, sometimes, gravelly sandy loam .
Subsoils are gravelly sand, coarse sand or sandy gravel . Stoniness varies, ranging from none on some parts o f
the fan aprons to excessively stony near the fan apexes .
Soil Moisture Characteristics : Chehalis soils are well to moderately well drained . They are rapidl y
pervious and have slow surface runoff and low water holding capacity . Some of the lower lying areas hav e
temporary, fluctuating watertables in the subsoil when the water levels in adjacent streams are high . Som e
potential for flooding exists during periods of prolonged, excessive rainfall and during rapid snowmelt .
General Soil Description : Chehalis soils usually have 5 cm or less of mixed deciduous and coniferou s
forest litter at the soil surface . This is underlain by 1 to 4 cm of grayish-brown, loose, partially leached, sand y
material which, in turn, is underlain by about 20 cm of loose or very friable, brown or yellowish-brown, sandy o r
gravelly material . This grades to loose, unweathered sand or gravel below about 30 cm . Soil reaction varies fro m
very strongly to extremely acid throughout . Soil classification is Eluviated Dystric Brunisol.
Commonly Associated Soils : Isar and Elk soils usually occur in close association with Chehalis soils . Isa r
soils differ from Chehalis soils by having little or no soil profile development while Elk soils differ by being poorl y
drained and having a black surface layer .
Vegetation : Some areas of Chehalis soils have ben cleared for agricultural and urban uses . Uncleared area s
support mixed stands of coast Douglas-fir, western red cedar, western hemlock, red alder, birch and others . Th e
understory includes salai, bracken, huckleberry and blackberry . Moss usually covers the soil surface . Rootin g
is generally unrestricted to at least 100 cm depth .
General Land Use Comments : (1) Agricultural suitability is limited by low water holding capacity, lo w
fertility and sometimes, stoniness . Adequate fertilization and irrigation is required for good crop production . (2 )
Chehalis soils are moderately suited for urban development although in some areas periodic high watertable s
may produce water in basements and other excavations ; some potential for occasional surface flooding als o
exists on the lower fan aprons . The soils are well suited for disposal of septic tank effluent although incomplet e
filtration by the coarse-textured subsoils may lead to contamination of the groundwater and adjacent streams .
(3) Forest growth appears to be moderately good, and productivity of coast Douglas-fir is estimated at about 8
to 10 m 3/ha/yr. Low soil water holding capacity is limiting during dry summer months .
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