Soils of the - Agriculture and Agri-Food Canada

KENWORTHY SOILS (KW)
Location and Extent : Kenworthy soils are located on the lower mountain slopes north of the Fraser River ,
mainly in Mission and Maple Ridge Municipalities . There are about 230 ha of pure map units and 920 ha of soi l
complexes dominated by Kenworthy soils . The complexes are mostly with Hoover, Cannell and Steelhead soils .
Topography and Elevation : Kenworthy soils are generally steeply to extremely sloping or sometimes ,
strongly rolling to very hilly. Most slope gradients are between 30 and 60 percent although some may be as lo w
as 20 percent or as high as 80 percent . Elevations range between 150 and 600 m above sea level .
Parent Material and Texture : The parent material of Kenworthy soils are mostly moderately coarse an d
some coarse-textured, somewhat unstable colluvial deposits, at least 1 m thick that contain some silty eolia n
material on or mixed into the surface . The deposits contain a very high proportion of angular gravel and stone -
sized rock fragments throughout. Surface, subsurface and subsoil textures vary from gravelly loamy sand t o
gravelly loam although gravelly sandy loam is the most common .
Soil Moisture Characteristics : Kenworthy soils are mostly well drained with some moderately well draine d
areas on lower slopes . They are rapidly pervious and have moderate to low water holding capacity and slow
surface runoff. Intermittent telluric seepage is usually present in the lower subsoil of areas located near the bas e
of long slopes .
General Soil Description : Kenworthy soils generally have 5 to 10 cm of well to undecomposed, organi c
forest litter on the mineral soil surface . Under this is 2 cm or less of discontinuous, grayish, leached, mineral
material which, in turn, is underlain by about 60 cm of friable, loamy to sandy material which varies from dar k
reddish brown in the upper part to reddish-brown or yellowish-brown in the lower part . It contains at least 4 0
percent (by volume) angular gravels and stones as well as common, fine, hard, reddish concretions . In turn, thi s
is underlain by a layer about 60 cm thick which is loose, dark yellowish brown or yellowish-brown, contains up t o
80 percent coarse fragments and is transitional to the colluvial soil parent material . The parent material is loos e
and contains up to 80 percent coarse fragments and common to few, yellowish or reddish mottles . Soil reaction s
vary from very strongly or extremely acid in the upper soils to medium acid in the subsoil . Soil classification i s
generally Orthic Humo-Ferric Podzol although a few, small inclusions of Orthic Dystric Brunisol or Orthi c
Regosol also occur where the soils are unstable .
Commonly Associated Soils : Cannell, Eunice, Hoover, Buntzen and Steelhead soils often occur in clos e
association with Kenworthy soils . Cannell and Eunice soils differ from Kenworthy soils by respectively, consisting
of less than 100 cm of mineral soil over bedrock and 10 cm or more of organic soil over rock . Hoover soil s
differ by containing substantially lower volumes of coarse fragments in the soil as well as overlying glacial till .
Buntzen and Steelhead soils have developed from glacial till and contain strongly cemented layers in th e
subsoil . Additionally, Steelhead soils are imperfectly drained .
Vegetation : The vegetation on Kenworthy soils consists generally of second-growth coast Douglas-fir ,
western hemlock and western red cedar with some red alder, vine maple and other deciduous species . Othe r
than moderate limitations imposed by high gravel and stone contents, rooting depths are essentially unrestricted
to at least 100 cm .
General Land Use Comments : (1) Very steep slopes and stoniness make Kenworthy soils unsuitable fo r
agricultural uses . (2) They are also unsuited for urban uses because of the steep slopes and unstable nature o f
the soils . Downslope soil creep is evident by soil accumulations on up-slope sides of trees, curved (pistol-butt) ,
lower parts of tree trunks, and stone stripes . (3) Forest growth is usually good although moisture deficiencie s
occur during long, dry periods . Potential annual wood production by Douglas-fir is estimated to be between 9
and 12 m 3/ha . When forest harvesting is undertaken, extreme care should be taken to prevent surface erosio n
and perhaps slumping in some areas . In the steeper areas, surface soil creep may cause problems with fores t
regeneration, either natural or planted .
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