Soils of the - Agriculture and Agri-Food Canada

SEYMOUR SOILS (Sl )
Location and Extent : Seymour soils occur mainly along the Coquitlam, Seymour and Alouette Rivers in th e
northern part of the map area. About 450 ha of pure map units and 1060 ha of soil complexes dominated b y
Seymour soils are mapped . The complexes are usually with Sardis, Judson, Shalish and Eastcap soils .
Topography and Elevation : The topography of Seymour soils varies from nearly level to gently sloping o r
undulating with slope gradients of less than 5 percent . Elevations range from about 20 to 150 m above sea level .
Parent Material and Texture : The parent material of Seymour soils consists of coarse-textured, stony ,
alluvial deposits, usually occurring as low terraces along the river margins . Surface textures are gravelly loam y
sand, gravelly sand or sandy gravel, usually stony . Subsurface and subsoil textures are mainly sandy gravel an d
are very stony and bouldery .
Soil Moisture Characteristics : Seymour soils are imperfectly drained . They are usually rapidly perviou s
although discontinuous cemented strata in some locations somewhat retard downward moisture movement .
Water holding capacity is low and surface runoff is slow . Seymour soil areas receive seepage from adjacent ,
higher lands and a fluctuating watertable is usually present which is related to the heighth of water in th e
adjacent streams . The soils are subject to periodic flooding during high runoff periods .
General Soil Description : Seymour soils generally have up to 15 cm of mostly well-decomposed, matted ,
dark reddish brown, organic forest litter on the soil surface . This is underlain by 2 to 5 cm of reddish-gray to gray,
friable, weakly structured, strongly leached, gravelly and sandy material which, in turn, is underlain by about 2 0
cm of friable to firm, weakly structured, dark reddish brown or dark brown, gravelly material . This layer i s
underlain by about 60 cm of variably coloured (dark brown, brown or reddish-brown), loose to firm, variabl y
cemented, gravelly material containing from 50 to 80 percent stones and boulders as well as common,reddis h
to yellowish mottles . This zone gradually grades to loose, stony and bouldery gravel below about 120 cm whic h
contains variable amounts of reddish and yellowish mottles and stains . Soil reaction grades from extremely aci d
in the upper soil to very strongly or strongly acid in the subsoil . Soil classification is mostly Gleyed Ferro-Humic
Podzo/although some Gleyed Ortstein Ferro-Humic Podzols and Duric Ferro-Humic Podzols are also present i n
areas where the subsurface and subsoil cementation is stronger than usual .
Commonly Associated Soils : Sardis, Eastcap, and Shalish soils are usually closely associated wit h
Seymour soils . Sardis and Eastcap soils differ from Seymour soils by having very little soil development (ar e
regosolic) while Shalish soils have developed from alluvial fan deposits and are well to moderately well drained .
Vegetation : The vegetation on Seymour soil consists mainly of second-growth forest, including coas t
Douglas-fir, western red cedar, western hemlock, red alder, black cottonwood and vine and bigleaf maple .
Rooting depth is variable, depending on height of the periodic watertable, strength of the discontinuou s
subsurface cementation and on the amount of stones and boulders in the subsoil .
General Land Use Comments : (1) Seymour soils are generally unsuited for agricultural use due to th e
stony and bouldery, coarse-textured nature of the soil . Periodic flooding hazard and low moisture holdin g
capacity also limit agricultural use . (2) Urban and similar uses are mainly unsuited . Periodic flooding is a hazar d
and basements and other excavations are likely to contain water during parts of the year . Stones and boulder s
make excavation difficult and potential ground water contamination may occur from septic tank disposal field s
due to poor filtration by the coarse-textured soil . (3) Forest growth is moderately good although periodic soi l
moisture deficiencies and restricted root distribution due to stones and boulders are somewhat limiting . Annua l
wood production by Douglas-fir and western red cedar is estimated to be about 7 .5 to 10 m 3 /ha .
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