The Soils of The Regional Municipality of Ottawa=Carleton

from clay to silty clay loam . In some Rideau soils, subsurface
beds of clay and silty clay are present, especially when these
soils were mapped in combination with soils of the Dalhousie
association . Subsurface layers of reddish brown to brown
heavy clay material may also be present in some Rideau soils,
especially those mapped in combination with soils of the
Bearbrook association . Clay content of the heavy clay parent
material of Rideau soils ranges from 61 to 80%, with average
clay content being 69% .
The parent material ofmost Rideau soils is noncalcareous
and neutral in soil reaction . Occasionally, however, some were
found to be mildly alkaline and contain small amounts of calcium
carbonates .
Soil reaction in the upper A and B horizons tends to be
slightly lowerthan in the parent material, and generally ranges
from slightly acid to neutral .
Soil Moisture Characteristics More than 90 01o of all Rideau
soils are poorly drained and remain saturated or nearly saturated
for extended periods during the growing season. These
soils occur on level to nearly level topography which results in
slow to very slow surface water runoff rates .
Approximately half of the remaining soils were classified
as imperfectly drained . These soils may be saturated for short
periods during the growing season . Imperfectly drained
Rideau soils are primarily found on very gently sloping topography
with slopes ranging from 2 to 5 076 . Slopes of this magnitude
permit moderate rates of surface water runoff.
The remaining portion of Rideau soils were classified as
very poorly drained. These soils remain saturated throughout
most of the year and are found on level to depressional topog
raphy. Most often these soils serve as catchment areas for both
surface and groundwater, and have water tables which remain
at or near the surface for most oftheyear.
Due mainly to their heavy texture, Rideau soils possess
high moisture holding capacity. Soil permeability is generally
moderate.
Soil Landscape Units Five units were identified for the
Rideau association . They are described as follows :
R1 : Dominantly imperfectly
drained soils
found on very gently to
gently sloping topography.
Slopes generally
range from 2to 9% .
R2 : Dominantlyimperfectly
drained soils
incombination with
significant areas of
poorly drained soils
found on nearly levelto
verygently sloping or
undulating topography.
Slopes generally
range from 1 to 5% .
R3 : Dominantly poorly
drained soils found
on level to nearly level
topography. Slopes
range from 0 to 2% .
Recognized Recognized
Subgroups Series
Gleyed Melanic Rideau
Brunisols
Gleyed Melanic Rideau
Brunisols (imperfect)
Orthic Humic Ste . Rosalie
Gleysols (poor)
Orthic Humic Ste . Rosalie
Gleysols
Recognized Recognized
Subgroups Series
R4 : Dominantly very
poorly drained soils
found on level to
depressionaltopography.
Slopes range from
0to 1% .
Rego Gleysols Laplaine
R5 : Dominantly poorly Orthic Humic Ste. Rosalie
drained soils in Gleysols (poor)
combination with Gleyed Melanic Rideau
significant areas Brunisols (imperfect)
ofimperfectly drained
soils found on very gentlyundulatingtopography.
Slopes range from
2to5% .
Taxonomic Components The imperfectly drained Rideau
series (Gleyed Melanic Brunisol subgroup) is subject to saturation
for short periods during the growing season . It possesses a
clay loam, silty clay loam, silty clay, clay or occasionally a
heavy clay surface horizon which usually is an Ap . The Ap is
often dark grayish brown in color, has granular structure, and
contains 3 to 4% organic matter.
The underlying B horizon is commonly a Bmgj and has
olive gray matrix colors with faint to distinct yellowish brown
mottles . Texture isdominantlyheavy clayand occasionally lay
ers of silty clay or clay may also occur. Structure is usually
angular to subangular blocky but occasionally may be prismatic
. The parent material or Cg horizon is commonly olive
gray in color and sometimes exhibits yellowish brown mottles.
Texture is dominantly heavy clay and structure is usually angular
blocky.
The poorly drained Ste. Rosalie series (Orthic Humic
Gleysol subgroup) is found on level or nearly level landscapes
which result in little or no surface water runoff. This factor in
combination with high moisture holding capacity of the soil
materials results in Ste. Rosalie soils being saturated for
extended periods during the growing season . The surface horizons
are dark olive gray to black in color and have subangular
blocky to granular structure . Organic matter content is 4 to
5%. Surface textures tend to have a lower clay content than in
the subsoil and most often are clay or silty clay. Occasionally
clay loam, silty clay loam, or heavy clay textures also occur.
The underlying Bg horizons are dominated by heavy clay, with
occasional layers of silty clay or clay also present at times .
Matrix colors are commonly dark grayish brown and prominent
dark yellowish brown mottles also are present . Structure
of the B horizons ranges from subangular and angular blocky
to columnar. The parent material or Cg horizons have heavy
clay textures andusually angular blocky soil structures. Matrix
colors are commonly olive gray, and yellowish brown prominent
mottles may also be present .
The very poorly drained Laplaine series (Rego Gleysol
subgroup) is subjectto saturation or near saturation conditions
for most ofthe year. These soils frequently have a surface hori
zon of humic peat which is 15 to 40 cm thick . They also have
parent materials which consist of massive olive gray to bluish
gray colored heavy clay. The subsoil above the parent material
at times may have yellowish brown mottles .