|
| |
NSSH Part 618 Exhibits
Soil Properties and Qualities
Guides for Estimating Risk of Corrosion Potential for Uncoated Steel 1/ (Exhibit 618-1)
| Property |
Limits |
| Low |
Moderate |
High |
| Drainage class and texture |
Excessively drained, coarse textured or well drained, coarse to medium textured soils; or moderately well
drained coarse textured, soils; or some- what poorly drained, coarse textured soils |
Well drained, moderate y fine textured soils; or moderately well drained, medium textured soils; or somewhat
poorly drained, moderately coarse textured soils; or very poorly drained soils with stable high water table |
Well drained, fine textured or stratified soils; or moderately well drained, fine and moderately fine textured
or stratified soils; or somewhat poorly drained, medium to fine textured or stratified soils; or poorly drained
soils with fluctuating water table |
| Total acidity (meq/100g) 2/ |
< 8 |
8 - 12 |
≥ 12 |
| Resistivity at saturation(ohm/cm) 3/ |
≥ 5,000 |
2,000 - 5,000 |
< 2,000 |
| Conductivity of saturated extract(mmhos cm-1) 4/ |
< 0.3 |
0.3 - 0.8 |
≥ 0.8 |
1/ Based on data in the publication “Underground Corrosion,” table 99,
p. 167, Circular 579, U.S. Dept. of Commerce, National Bureau of Standards.
2/ Total acidity is roughly equal to extractable acidity (as determined by Soil Survey Laboratories Method 6Hla,
Soil Survey Investigations Report No. 42, Soil Survey Laboratory Methods Manual, Version 4.0, November 2004).
3/ Roughly equivalent to resistivity of fine-and medium-textured soils measured at saturation (Method 8E1,
Soil Survey Investigations Report No. 42, Soil Survey Laboratory Methods Manual, Version 4.0, November 2004). Resistivity
at saturation for coarse-textured soil is generally lower than when obtained at field capacity and may cause the soil to be
placed in a higher corrosion class.
4/ Method 8Ala, Soil Survey Investigations Report No. 42, Soil Survey Laboratory Methods Manual, Version 4.0,
November 2004. The relationship between resistivity of a saturated soil paste (Method 8E1) and electrical conductivity of
the saturation extract (Method 8A1a), is influenced by variations in the saturation percentage, salinity, and conductivity
of the soil minerals. These two measurements generally correspond closely enough to place a soil in one corrosion class.
Guide for Estimating Risk of Corrosion Potential for Concrete (Exhibit 618-2)
| Property |
Limits 1/ |
| Low |
Moderate |
High |
| Texture and reaction |
Sandy and organic soils with pH>6.5 or medium and fine textured
soils with pH>6.0 |
Sandy and organic soils with pH5.5-6.5 or medium and fine
textured soils with pH 5.0 to 6.0 |
Sandy and organic soils with pH<5.5 or medium and fine textured
soils with pH<5.0 |
Na and/or Mg sulfate
(ppm) |
Less than 1000 |
1000 to 7000 |
More than 7000 |
| NaCl (ppm) |
Less than 2000 |
2000 to 10000 |
More than 10000 |
1/ Based on data in National Handbook of Conservation Practices, Standard 606,
Subsurface Drain, 1980.
Crop Names and Units of Measure (Exhibit 618-3)
(Refer to the data dictionary of the National Soil Information System for crop_names and crop_yield_units in
http://nasis.nrcs.usda.gov/documents/metadata/5_3/n53clr.pdf.
Classification of Soils and Soil-Aggregate Mixtures for the AASHTO System (Exhibit 618-4)
| General Classification |
Granular Materials
(35% of less passing No. 200) |
Silt-Clay Materials
(More than 35% passing No. 200) |
| Group Classification |
A-1 |
A-3 |
A-2 |
A-4 |
A-5 |
A-6 |
A-7 |
| A-1-a |
A-1-b |
A-2-4 |
A-2-5 |
A-2-6 |
A-2-7 |
A-7-5
A-7-6 |
Sieve analysis,
% passing
No. 10
No. 40
No 200 |
50 max
30 max
15 max |
-
50 max
25 max |
-
51 max
10 max |
-
-
35 max |
-
-
35 max |
-
-
35 max |
-
-
35 max |
-
-
36 min |
-
-
36 min |
-
-
36 min |
-
-
36 min |
Characteristics
of fraction
passing No. 40
Liquid limits
Plasticity index |
-
6 max |
-
NP |
40 max
10 max |
41 max
10 max |
40 max
11 min |
41 min
11 min |
40 max
10 max |
41 min
10 max |
40 max
11 min |
*
41 min
11 min |
Usual types of
significant
constituent
materials |
Stone fragments,
gravel and sand |
Fine
sand |
Silty or clayey gravel and sand |
Silty soils |
Clayey soils |
General rating
as subgrade |
Excellent to good |
Fair to good |
* Plasticity index of A-7-5 subgroup is equal to or less than LL minus 30. Plastaicity index of A-7-6 subgroup is
greater than LL minus 30.
Potential Frost Action (Exhibit 618-5)
| Soil moisture regime |
Frost action classes 1/, 2/ |
| Low |
Moderate |
High 3/ |
| Aquic |
Cindery, Fragmental, Pumiceous |
Sandy, Sandy-skeletal |
Coarse-loamy, Fine-loamy, Coarse-silty, Fine-silty, Loamy-skeletal, Clayey and clayey skeletal, Organic soil
materials, Ashy, ashy- pumiceous, and ashy-skeletal, Medial, medial- pumiceous, and medial-skeletal, Hydrous-
pumiceous, Hydrous-skeletal, Hydrous |
| Udic, Xeric, Ustic (when irrigated), Aridic (when irrigated) |
Fragmental, Cindery, Sandy, Sandy-skeletal, Pumiceous |
Coarse-loamy, Fine-loamy, Loamy-skeletal, Clayey, Clayey-skeletal, Ashy-pumiceous, Ashy-skeletal,
Hydrous-skeletal, Medial-skeletal, Medial-pumiceous |
Coarse-silty, Fine-silty, Ashy Medial, Hydrous- pumiceous, Hydrous |
| Ustic, Aridic |
Fragmental, Sandy, Sandy-skeletal, Clayey, Clayey-skeletal, Cindery, Ashy, ashy- pumiceous, and ashy-skeletal,
Medial and medial-skeletal, Pumiceous |
Coarse-loamy, Fine-loamy, Coarse-silty, Fine-silty, Loamy-skeletal, Medial-pumiceous, Hydrous-pumiceous,
Hydrous-skeletal, Hydrous |
|
1/ Taxonomic family particle-size classes apply to the whole soil to the depth of frost penetration, which is
not necessrily the same as the taxonomic family particle-size control section.
2/ Isomesic and warmer temp regimes would have a “none” frost action class.
3/ Organic soil materials with a mesic or greater temperature regime and a udic moisture regime (e.g. Folists)
have “high” frost action class.
Distribution of Design Freezing Index Values in the Continental United States (Exhibit 618-6)
High resolution JPEG
(3936x2370, 1.34 MB)
Estimating LL and PI from Percent and Type of Clay (Exhibit 618-7)
The following two formulas provide estimates of liquid limit and plasticity index. These calculations are included in the
National Soil Information System and provide default values to LL and PI.
LL = 11.60 + [1.49 x 15 bar water %] + [1.35 x org. carbon %] + [0.6 x LEP] + [0.26 x non-carbonate clay %]*
where:
LL is liquid limit
LEP is Linear Extensibility Percent
PI = -1.86 + [0.69 x 15 bar water %] - [1.19 x organic carbon %] +[ 0.13 x LEP] +[0.47 x non-carbonate clay %]*
where:
PI is Plasticity Index
LEP is Linear Extensibility Percent
* When the calculated PI < 0.5, the PI is set to zero (nonplastic). When the calculated LL < 15 or PI < 0.5, the LL is set
to zero.
Texture Triangle and Particle-Size Limits of AASHTO, USDA, and Unified Classification Systems
(Exhibit 618-8)
High resolution JPEG
(2078x2400, 1.19 MB)
Guide for Estimating Ksat from Soil Properties (Exhibit 618-9)
Estimate saturated hydraulic conductivity (Ksat) from soil texture by first selecting the bulk density class of medium, low
or high. Then use the corresponding textural triangle to select the range of saturated hydraulic conductivity in mms-1.
Overrides follow.
High resolution JPEG
(2100x3150, 967 KB)
Use these overrides in lieu of the textural guide above when these conditions exist. A single property statement
is sufficient for an override from the textural guide.
| Overriding condition |
Saturated hydraulic conductivity (μmm s-1 ) |
| All fragmental, cindery or pumiceous |
≥ 100 |
| Many medium or coarser vertical pores that extend through the layer. |
≥ 100 |
| Medial-pumiceous, medial-skeletal, ashy-pumiceous, ashy-skeletal, hydrous-pumiceous that is very friable, friable,
soft, or loose. |
10 – 100 |
| When moderately moist or wetter, structure that is moderate or strong granular, strong blocky or prismatic smaller
that is very coarse and no stress surfaces or slickensides. |
10 – 100 |
| Common medium or coarser vertical pores that extend through the layer. |
10 – 100 |
| Strong very coarse blocky or prismatic and no stress surfaces or slickensides. |
1 – 10 |
| ≥ 35 percent clay, soft, slightly hard, very friable or friable, no stress surfaces or slickensides and the
clay is subactive after subtracting the quantity (2 x (OC x 1.7)) |
1 – 10 |
| Few stress surfaces and/or slickensides. |
0.1 – 1 |
| Massive and very firm or extremely firm, or weakly cemented. |
0.1 – 1 |
| Continuously moderately cemented. |
0.1 – 1 |
| Common or many stress surfaces and/or slickensides. |
0.01 - 0.1 |
| Continuously indurated or very strongly cemented. |
< 0.01 |
Guide to Estimating Water Movement Through Lithic and Paralithic Materials. 1/ 2/ (Exhibit 618-10)
| Material |
Water Movement μm s-1 |
| Sandstone
unfractured
fractured
weathered
|
<10
10-100
10-100
|
| Limestone
unfractured
fractured
weathered
|
<1
<10
<10
|
| Limestone, Karst |
> 100 |
| Shales and Mudstones
consolidated
weathered
|
<1
<10
|
| Igneous and Metamorphic Rocks
unfractured
fractured
weathered |
<1
1 - 100
<1
|
1/ This table is to be used as a guide and may be adjusted to reflect local, regional, or state bedrock permeability
data. Fracturing may increase hydraulic conductivity of consolidated rock by a factor of 104 to 106, which is dependent
on the degree and interconnection of fracturing. (Freeze and Cherry, 1979; Legget and Karrow, 1983).
2/ This table assumes that materials are level bedded. Tilted beds of some materials may have rapid rates of water
movement that goes directly to an aquifer.
3/ Haan, C.T., Barfield, B.J., and Hayes, J.C.; Design Hydrology and Sedimentaology for Small Catchments.
Rock Fragment Modifier of Texture (Exhibit 618-11)
Instructions for Table 1, Guide for determining rock fragment
modifier of texture: First choose the row with the appropriate total
rock fragments. Then read the criteria in the columns under “Gravel, cobbles,
stones and boulders,” starting from the left-most column and proceeding to the
right. Stop in the first column in which a criterion is met.
Table 1 – Guide for determining rock fragment
modifier of texture.
Click
here for an MSExcel spreadsheet that calculates the texture modifiers
for flat and nonflat rock fragments.
Total Rock
Fragments
(Vol %) |
Gravel (GR), cobbles (CB), stones (ST), and boulders
(BY)
(Substitute channers for gravel, and flagstones for cobbles, where
applicable)1 |
| IF GR ≥ 1.5 CB + 2 ST + 2.5 BY |
IF CB ≥ 1.5 ST + 2 BY |
IF ST ≥ 1.5 BY |
IF ST < 1.5 BY |
| ≥ 15 < 35 |
Gravelly |
Cobbly |
Stony |
Bouldery |
| ≥ 35 < 60 |
Very Gravelly |
Very Cobbly |
Very Stony |
Very Bouldery |
| ≥ 60 < 90 |
Extremely Gravelly |
Extremely Cobbly |
Extremely Stony |
Extremely Bouldery |
| ≥ 90 |
Gravel |
Cobbles |
Stones |
Boulders |
|
Example: Determine the rock fragment modifier for a soil that contains
15 percent gravel (GR), 10 percent cobbles (CB), and 3 percent stones (ST).
- Since total rock fragments are 28 percent, choose the first row (≥ 15
and < 35).
- Under “Gravel (GR), cobbles (CB), stones (ST), ...”, test the
criterion in the left-most column.
Is 15%GR ≥ 1.5 (10% CB) + 2 (3% ST)? Answer: NO.
- Proceed to the next column.
Is 10%CB ≥ 1.5 (3% ST)? Answer: YES. STOP. The modifier is Cobbly.
1 If both flat and nonflat rock fragments are present, the
quantity in each size class is summed (e.g. gravel + channers, cobbles +
flags). The sums are used to determine the appropriate quantity/size
modifier. If the amount of flat and nonflat rock fragments within any
given size class are equal, the nonflat modifier takes precedence. For
example, if there are 10 percent gravel and 10 percent channers, the
modifier is gravelly. |
Soils with pararock fragments only – The same basic weighting rules apply
with parafragments as with flat and nonflat rock fragments. However, the above
spreadsheet only outputs modifier terms for rock fragments. To assign the
correct pararock fragment modifier to the outputted rock modifier term, simply
precede the modifier with “para.” For example, if the calculator outputs “very
cobbly,” the correct modifier is “very paracobbly.”
Soils with both rock and pararock fragments – Refer to instructions in
NSSH
618.67.h.2.vii.
Soil Erodibility Nomograph (Exhibit 618-12)
High resolution JPEG
(1660x2400, 405 KB)
Kw Value Associated with Various Fragment Contents (Exhibit
618-13)
| Fragment vol. % |
Mulch factor 1/ |
Kf value classes of less than 2 mm soil fraction |
| .10 |
.15 |
.20 |
.24 |
.28 |
.32 |
.37 |
.43 |
.49 |
.55 |
.64 |
| 5 |
.90 |
.09 |
.14 |
.18 |
.22 |
.25 |
.29 |
.33 |
.39 |
.44 |
.50 |
.58 |
| 10 |
.77 |
.08 |
.12 |
.15 |
.18 |
.22 |
.25 |
.28 |
.33 |
.38 |
.42 |
.49 |
| 15 |
.68 |
.07 |
.10 |
.14 |
.16 |
.19 |
.22 |
.25 |
.29 |
.33 |
.37 |
.43 |
| 20 |
.61 |
.06 |
.09 |
.12 |
.15 |
.17 |
.20 |
.23 |
.26 |
.30 |
.37 |
.39 |
| 25 |
.54 |
.05 |
.08 |
.11 |
.13 |
.15 |
.17 |
.20 |
.23 |
.26 |
.30 |
.35 |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| 30 |
.48 |
.05 |
.07 |
.10 |
.12 |
.13 |
.15 |
.18 |
.21 |
.24 |
.26 |
.31 |
| 35 |
.43 |
.04 |
.06 |
.09 |
.10 |
.12 |
.14 |
.16 |
.18 |
.21 |
.24 |
.28 |
| 40 |
.38 |
.04 |
.06 |
.08 |
.09 |
.11 |
.12 |
.14 |
.16 |
.19 |
.21 |
.24 |
| 45 |
.34 |
.03 |
.05 |
.07 |
.08 |
.10 |
.11 |
.13 |
.15 |
.17 |
.19 |
.22 |
| 50 |
.30 |
.03 |
.05 |
.06 |
.07 |
.08 |
.10 |
.11 |
.13 |
.15 |
.17 |
.19 |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| 55 |
.26 |
.03 |
.04 |
.05 |
.06 |
.07 |
.08 |
.09 |
.11 |
.13 |
.12 |
.14 |
| 60 |
.22 |
.02 |
.03 |
.04 |
.05 |
.06 |
.07 |
.08 |
.09 |
.11 |
.12 |
.14 |
| 65 |
.19 |
.02 |
.03 |
.04 |
.05 |
.05 |
.06 |
.07 |
.08 |
.09 |
.10 |
.12 |
| 70 |
.16 |
.02 |
.02 |
.03 |
.04 |
.04 |
.05 |
.06 |
.07 |
.08 |
.09 |
.10 |
| 75 |
.13 |
.01 |
.02 |
.03 |
.04 |
.04 |
.04 |
.04 |
.06 |
.06 |
.07 |
.08 |
| |
|
|
|
|
|
|
|
|
|
|
|
|
| 80 |
.10 |
.01 |
.02 |
.02 |
.02 |
.03 |
.03 |
.04 |
.04 |
.05 |
.06 |
.06 |
| 85 |
.08 |
.01 |
.02 |
.02 |
.02 |
.02 |
.03 |
.03 |
.03 |
.04 |
.04 |
.05 |
| 90 |
.06 |
.01 |
.01 |
.01 |
.01 |
.02 |
.02 |
.02 |
.03 |
.03 |
.03 |
.04 |
| 95 |
.04 |
.01 |
.01 |
.01 |
.01 |
.01 |
.01 |
.02 |
.02 |
.02 |
.02 |
.03 |
| 100 |
.03 |
.01 |
.01 |
.01 |
.01 |
.01 |
.01 |
.01 |
.01 |
.02 |
.02 |
.02 |
1/ Mulch factor is the ratio of the soil loss from soils with the specified fragment volumes to that from soils with
no fragments. The table was constructed from the zero canopy curve, figure 6, page 19 in AH 537 (USDA-SEA 1978).
General Guidelines for Assigning Soil Loss Tolerance “T” (Exhibit 618-14)
Soil loss tolerance “T” is assigned according to properties of root
limiting subsurface soil layers. The designation of a limiting layer implies
that the material above the layer has more favorable plant growth
properties. As limiting or less favorable soil layers become closer to the
surface, the relative ability of a soil to maintain its productivity through
natural and managed processes decreases.
Criteria for assigning “T” are estimated from:
- The severity of physical or chemical properties of subsurface layers.
- The climatically influenced properties of soil moisture and
temperature.
- The economic feasibility of utilizing management practices to overcome
limiting layers or conditions.
The following general guide was used with specific soil properties and
conditions to write criteria statements for programming “T” factors at Iowa
State University Statistical Laboratory.
Depth to limiting
layer (inches) |
Soil loss tolerance in tons/acre |
| Group 1 |
Group 2 |
Group 3 |
| 0 - 10 |
1 |
1* |
3 |
| 10 - 20 |
1 |
2 |
3 |
| 20 - 40 |
2 |
3 |
4 |
| 40 - 60 |
3 |
4 |
4 |
| >60 |
5 |
5 |
5 |
* Some soils are assigned with soil loss tolerance of 2.
Group 1 -- The limitations are significant or have permanent layers of
root limitation.
Group 2 -- The limitations are of moderate root restriction, or have a
less than permanent loss to productivity in a given climate.
Group 3 -- The limitations can be overcome in a given climate, through
natural or managed processes to achieve the productivity level of the
non-eroded soil.
“T” Criteria
(3/11/1995)
Bedrock
Definition A: Soils in all Land Resource Regions except W, X, and Y
having SOFT identified in the Bedrock soil property block or MARL (marl
layers) with the beginning depth of:
| Depth limit (inches) |
T Value |
| <10 |
1 |
| 10-20 |
2 |
| 20-40 |
3 |
| 40-60 |
4 |
| >60 |
5 |
|
“T” Criteria
3/11/1995 |
| Soil Characteristic |
Definition |
Depth limit (inches) |
T Value |
| 1. Bedrock |
A. Soils in all Land Resource Regions except W, X, and Y
having SOFT identified in the Bedrock soil property block or MARL (marl
layers) with the beginning depth of: |
<10
10-20
20-40
40-60
>60 |
1
2
3
4
5 |
|
OR |
|
|
| |
B. Soils having HARD identified in the Bedrock soil property
block or layers identified as ICE with the beginning depth of: |
<20
20-40
40-50
>60 |
1
2
3
5 |
|
OR |
|
|
| |
C. Soils in only Land Resource Regions W, X, and U having
SOFT identified in the Bedrock soil property block or MARL (marl layers)
with the beginnign depth of: |
<20
20-40
40-60
>60 |
1
2
3
5 |
| 2. Cemented pans1 |
A. Soils in all Land Resource
Regions except W, X, and
Y having duripan,
petrocalcic, petrogypsic,
petroferric with THIN in
Cemented Pan block and CEM in
lieu of texture OR THIN or
THICK if IND or CEM are not
shown in lieu of texture
with the beginning depth of:
|
<20
20-40
40-60
>60 |
2
3
4
5 |
|
OR |
|
|
| |
B. Soils in all Land Resource
Regions except W, X, and
Y having duripan,
petrocalcic, petrogypsic,
petroferric with
THICK in Cemented Pan
block and CEM and/or IND in
lieu of texture
or THIN in Cemented
Pan Block and IND in lieu of
texture with the beginning
depth of:
|
<20
20-40
40-60
>60 |
1
2
3
5 |
|
OR |
|
|
| |
C. Soils in only Land
Resource Regions W, X, and Y
having duripan,
petrocalcic, petrogypsic,
petroferric with THIN in
Cemented Pan block and CEM in
lieu of texture OR THIN or
THICK if IND or CEM are not
shown in lieu of texture
with the beginning depth of:
|
<20
20-40
40-60
>60 |
1
2
3
5 |
| 3. Fragmental/ Cindery |
A. Soils in all Land Resource Regions except W, X, and Y
having an upper layer that has a texture term other than SG, G, FRAG, or
CIND immediately above a layer of G, FRAG or CIND beginning at depth of: |
<10
10-20
20-40
40-60
>60 |
1
2
3
4
5 |
| |
B. Soils in Land Resource
Regions W, X, and Y
having an upper layer
that has a texture term other
than SG, G, FRAG, or CIND
immediately above a layer of G,
FRAG or CIND beginning at
depth of:
|
<20
20-40
40-60
>60 |
1
2
3
5 |
| 4. Fragipan |
Soils having a FRAGI great
group. Layer selected has the
greatest bulk density inflection,
(layer selected has the maximum
change which was determined by
evaluating all adjacent layers that
change from a lower bulk density to
a higher bulk density) and
a permeability less than or
equal to 0.2 inches per hour,
beginning at a depth of:
|
<20
20-60
>60 |
3
4
5 |
| 5. Natric |
A. Soils designated in great
groups of Natraquolls or
Natraqualfs or subgroups
of Natric Duraquolls but
exclude subgroups of Glossic
in the great group of
Natraqualfs; and have
a natric horizon (to find the
natric horizon: search for a
subsoil, subsurface, layer with
the slowest permeability [<0.2
inches/hour] above a layer,
if present, with UWB, WB,
CEM, or IND and use the upper
depth of that layer to assign depth
to natric horizon) beginning at a depth of: |
<20
20-40
40-60
>60 |
2
3
4
5 |
| |
B. Use criterion B in MLRA’s
48A, 48B, 49, 52, 53A, 53B,
53C, 54, 55A, 55B, 55C,
56, 58A, 58B, 58C, 58D, 60A,
60B, 61, 62, 63A, 63B, 64
through 79, 8OA, 8OB, 81,
82, 83A, 83B, 83C, 83D, 84A,
84B, 84C, 85, 86, 87, 102A, and 102B.
Soils designated in great
groups of Natralbolls,
Natriborolls, Natrustolls,
*Natriborals, Natrustalfs
Natrargids, Nadurargids, or
subgroups of Natric Durustolls
but exclude subgroups of Glossic
in great groups of Natriborolls,
Natrustolls, Natriboralfs,
Natrustalfs, and Natrargids; and
have a natric horizon (to find the
natric horizon: search for a
subsoil, subsurface, layer with
the slowest permeability (<0.2
inches/hour] above a layer,
if present, with UWB, WB,
CEM, or IND and use the upper
depth of that layer to assign depth
to natric horizon) beginning at a
depth of:
*At present, Natriboralfs are rare in the
United States, and subgroups
have not been developed. |
<20
20-40
40-60
>60 |
2
3
4
5 |
| |
C. Soil designated in great
group with “NA” and suborder “UD” and a subsurface natric
horizon with a slow or very
slow permeability (to find the
natric horizon: search for a
subsoil, subsurface, layer with
the slowest permeability [<0.2
inches/hour] and use the upper
depth of that layer to assign
depth to natric horizon)
beginning at a depth of:
|
<20
20-60
>60 |
3
4
5 |
| |
D. Soils in Land
Resource Regions A,
B, C, D, and E except
MRLA’s 48A, 48B, and 49
having a subsurface
natric horizon with
equal to or greater
than 35 percent clay;
slow or very slow permeability
(to find the
natric horizon: search for a
subsoil, subsurface, layer with
the slowest permeability [<0.2
inches/hour and equal to or
more than 35 percent
clay] and use the upper
depth of that layer to assign depth
to natric horizon); and
with aridic or xeric
soil moisture regime
and in great groups
designated as Nadurargids, Natrixerolls
Natrargids, or Natrixeralfs
or subgroups of Natric
Durixeralfs or Aridic
Natrixerolls with the slow or very slow permeability beginning at a depth
of: |
<20
20-40
40-60
>60 |
2
3
4
5 |
| 6. Sandy or Sandy Skeletal Substratum |
A. Soils in all Land Resource
Regions except A, B, C, D,
E, W, X , and Y and MLRA’s
52, 58A, 60B, 101, 140 141,142,143,144A,
144B 145, and 146
having sandy substratum
layer(s) of SG, COS, S, LS, FS,
or LCOS (with or without rock
fragment modifiers); or SR
with these textures; that
extend to a depth of 60 inches
or more; with a permeability
equal to or greater than
6 inches per hour (A) immediately
below a layer or layers that
have (1) a permeability of
less than 6 inches per hour,
(2) less than 50 percent fine
or coarser sand separates in
the fine earth fraction, and
(3) a combined thickness of
equal to or more than 10 inches;
OR (B) immediately below a layer
or layers that have (1) CE,
DE, FB, HM, MPT, MUCK, PEAT, or SP in lieu of texture, and (2) a combined
thickness of equal to or more than 10 inches. With a substratum beginning at
a depth of: |
10-20
20-60
>60 |
3
4
5 |
|
OR |
|
|
| |
B. Soils in Land Resource Regions
A, B, C, D, and E and MLRA’s
52, 58A, 60B, 101, 140, 141,
142,143, 144A, 144B 145, and
146 having sandy substratum
layer(s) of SG, COS, S, LS, FS,
or LCOS (with or without rock
fragment modifiers); or SR
with these textures; that
extend to a depth of 60 inches
or more; with a permeability
equal to or greater than
6 inches per hour (A) immediately
below a layer or layers that
have (1) a permeability of
less than 6 inches per hour,
(2) less than 50 percent fine
or coarser sand separates in
the fine earth fraction, and
(3) a combined thickness of
equal to or more than 10 inches;
OR (B) immediately below a layer
or layers that have (1) CE,
DE, FB, HM , MPT, MUCK, PEAT, or SP in lieu of texture, and (2) a combined
thickness of equal to or more than 10 inches. With a substratum beginning at
a depth of: |
10-20
20-40
40-60
>60 |
2
3
4
5 |
|
OR |
|
|
| |
C. Soils in Land
Resource Regions W, X, and Y
having sandy substratum
layer(s) ot SG, COS, S, LS, FS,
or LCOS (with or without rock
fragment modifiers); or SR
with these textures; that
extend to a depth of 60 inches
or more; with a permeability
equal to or greater than
6 inches per hour (A) immediately
below a layer or layers that
have (1) a permeability of
less than 6 inches per hour,
(2) less than 50 percent fine
or coarser sand separates in
the fine earth fraction; and
(3) a combined thickness of
equal to or more than 10 inches;
OR (B) immediately below a layer
or layers that have (1) CE,
DE, FB, HM, MPT, MUCK, PEAT,
or SP in lieu of texture, and
(2) a combined thickness of
equal to or more than 10 inches.
With a substratum beginning at
a depth of:
|
10-20
20-40
40-60
>60 |
1
2
3
5 |
| 7. Abrupt Textural Change |
A. Soils in orders of Alfisols,
Aridisols, Mollisols, or
Ultisols and
(1) all Pale great groups of
those orders, Albaqualfs
or Argialbolls; or
(2) soils in xer, bor, alb,
arg, aqu, or argi
suborders with great groups
of alb, argi, eutro, dur,
or cry with subgroups
of Abruptic, Abruptic Aridic,
Abruptic Cryic or Abruptic
Xerollic; or
(3) Alfic Haploxerands or Alfic
Vitrixerands
with an argillic horizon
with equal to or greater than
35 percent clay;
AND having
an adjacent upper layer
with a permeability of more
than 0.6 inches/hour
overlying and adjacent to a
lower layer having more than
35 percent clay with a
permeability of less than 0.2
inches/hour
|
OR
having an adjacent upper layer
with permeability greater than
0.2 inches per hour overlying
and adjacent to a lower layer
having equal to or more than
35 percent clay with a
permeability of less than
0.06 inches per hour beginning
at a depth of:
Criteria A. will be used in the
following MLRA’s 1, 2, 3, 4, 5, 6,
8 through 10, 10A, 11, llA, llB,
12 through 15, 17 through 27, 28A,
28B, 29 through 32, 34, 35, 37,
39, 40, 41, 43, 44, 47, 48A, 48B,
52, 53A, 54, 58A, 58B,
60A, 60B, and 67.
|
<20
20-60
>60 |
3
4
5 |
| |
B. Soils in orders of Alfisols,
Mollisols, or Ultisols and;
(1) Albaqualfs with subgroups of
Udollic, Aeric, Mollic, or Typic;
or (2) Hapludalfs with subgroups
of Albaquultic or Albaquic; or
(3) Typic Argialbolls; (4) Abruptic
Argiaquolls; or (5) Albaquults
with subgroups of Typic or Aeric with
an argillic horizon with equal
to or more than 35 percent clay;
AND having an adjacent upper
layer with a permeability of
more than 0.6 inches/hour
overlying and adjacent to a lower
layer having more than 35 percent
clay with a permeability of less than
0.2 inches/hour
OR
having an adjacent upper layer
with permeability greater than
0.2 inches per hour overlying
and adjacent to a lower layer
having equal to or more than
35 percent clay with a
permeability of less than
0.06 inches per hour beginning
at a depth of:
Criteria B. will be used in the
following MRLA’s: 71, 73, 74, 75,
76, 102B, 106, 107, 108, 109,
111, 112, 113, 114, and 115.
|
<20
20-60
>60 |
3
4
5 |
| |
C. Soils in orders of Alfisols
and Mollisols with an
arglllic horizon with equal
to or more than 35 percent
clay: AND having an adjacent
upper layer with permeability
greater than 0.6 inches per
hour overlying and adjacent
to a lower having equal to
or more than 35 percent clay
with a permeability of less
than 0.2 inches per hour;
OR
having an adjacent upper layer
with permeability greater than
0.2 inches per hour overlying
and adjacent to a lower layer
having equal to or more than
35 percent clay with a
permeability of less than
0.06 inches per hour
beginning at a depth of:
Criteria C. will be used in the
following MLRA’s 108, 109, 110, 113,
114, 115, 115A, 115B, and 115C.
|
<20
20-60
>60 |
3
4
5 |
| 8. Dense Layer |
A. Soils having a layer
whose upper boundary begins at the depths
indicated and has the following average bulk
density for layer soil textural class(s); and
with permeability difference of 2 classes
between dense layer and upper adjacent layer.
(excluding Vertisols, and Vertic subgroups)
(not used in Land Resource Regions R, W, X,
and Y and MLRA’s 100 and 101):
|
|
|
|
|
Layer Depth |
T Value |
| Layer Soil Textural Class2 |
Moist Avg. BD |
| COS, S, LCOS, LS, FS,LFS |
>1.80 |
<20
20-60
>60 |
3
4
5 |
| VFS, LVFS, FSL, COSL
VFSL, SL, with
average <18 percent clay.
|
>1.75 |
<20
20-60
>60 |
3
4
5 |
| COSL, VFSL, FSL, SL, or
CL and average 18 to
35 percent clay or L or SCL |
>1.7 |
<20
20-60
>60 |
3
4
5 |
| SI, SIL, or SICL
and average
<35 percent clay. |
>1.6 |
<20
20-60
>60 |
3
4
5 |
| CL, SC, C, SICL, SIC
and clay average within
35 to 60 percent clay. |
>1.55 |
<20
20-60
>60 |
3
4
5 |
| C with average clay
value 60 percent or more
clay (exclude Soil Orders
of Andisols and Oxisols). |
>1.35 |
<20
20-60
>60 |
3
4
5 |
|
OR |
|
|
| |
B. Soils in Land Resource Regions W, X,
and Y for soils having a layer
whose upper boundary begins at the depths
indicated and has the following average bulk
density for layer soil textural class(s); and
with permeability difference of 2 classes
between dense layer and upper adjacent layer.
excluding Vertisols, and Vertic subgroups): |
|
|
|
|
Layer Depth |
T Value |
| Layer Soil Textural Class2 |
Moist Avg. BD |
| COS, S, LCOS, LS, FS,
LFS |
>1.80 |
<20
20-40
40-60
>60 |
1
2
3
5 |
| VFS, LVFS, FSL, COSL,
VFSL, or SL with
average <18 percent clay. |
>1.75 |
<20
20-40
40-60
>60 |
1
2
3
5 |
| COSL, VFSL, FSL, SL, or
CL and average 18 to
35 percent clay or L or SCL |
>1.7 |
<20
20-40
40-60
>60 |
1
2
3
5 |
| SI, SIL, or SICL
and average
<35 percent clay. |
>1.6 |
<20
20-40
40-60
>60 |
1
2
3
5 |
| CL, SC, C, SICL, SIC
and average within
35 to 50 percent clay. |
>1.55 |
<20
20-40
40-60
>60 |
1
2
3
5 |
| C with average clay
value 60 percent or more
clay (exclude Soil Orders
of Andisols and Oxisols). |
>1.35 |
<20
20-40
40-60
>60 |
1
2
3
5 |
|
OR |
|
|
|
C. Soils in Land Resource Region R
and MLRA’s 100 and 101 having a
layer whose upper boundary begins
at the depths indicated and has the
following average bulk density
for layer soil textural class(es):
|
|
|
|
|
Layer Depth |
T Value |
| Layer Soil Textural Class2 |
Moist Avg. BD |
| COS, S, LCOS, LS, FS,
LFS |
>1.80 |
<20
20-40
40-60
>60 |
2
3
4
5 |
| VFS, LVFS, FSL, COSL
VFSL, or SL with
average <18 percent clay. |
>1.75 |
<20
20-40
40-60
>60 |
2
3
4
5 |
| COSL, VFSL, FSL, SL, or
CL and average 18 to
35 percent clay or L or SCL |
>1.7 |
<20
20-40
40-60
>60 |
2
3
4
5 |
| SI, SIL, or SICL
and average
<35 percent clay. |
>1.6 |
<20
20-40
40-60
>60 |
2
3
4
5 |
| CL, SC, C, SICL, SIC
and average
35 to 60 percent clay. |
>1.55 |
<20
20-40
40-60
>60 |
2
3
4
5 |
| C with average
50 percent or more
clay |
>1.35 |
<20
20-40
40-60
>60 |
2
3
4
5 |
|
OR |
|
|
|
D. Soils in Land Resource
Regions W, X, and Y that
have a combined surface
layer of 10 inches or more
thick with a bulk density less than
1.10 and 95percent or more material
passing the #10 sieve
overlying a layer with soil
textural modifiers of CB,
CBV, CBX, ST, STV, or STX or less than 85 percent passing the #10 sieve: |
<20
20-40
40-60
>60 |
1
2
3
5 |
| 9. Rock Fragments |
If state equals CT, DE, MA,
MD, ME, NH, NJ, NY, PA, RI, VT
VA, and WV, use only the 2mm - 10
inch rock fragment fraction
for the surface layer.
|
|
|
|
A. Soils in all Land Resource
Regions except W, X, and
Y having layer(s) with
a combined thickness of equal
to or more than 10 inches with
(1) Texture with no rock
fragment modifier, or (2)
texture modified by BY,
CB, GR, ST, CN, OR FL
(in the Northeast states, this
layer has 0 to 50 percent rock
fragments by weight;
texture modifiers are not used.),
or (3) CE, DE, FB, HM, MPT,
MUCK, PEAT, SP, VAR
over a layer that extends to a
depth of 60 inches or more that
has a texture (exclude SG, COS, S,
LS, FS, or LCOS) modified by BYX,
CBX, GRX, STX, CNX, or FLX or
over bedrock, CEM, or IND if
texture modified by BYX,
CBX, GRX, STX, CNX, or FLX
extends to less than 50 inches,
beginning at a depth of:
|
<20
20-60
>60 |
3
4
5 |
|
OR |
|
|
|
B. Soils in Land Resource
Regions W, X, and Y
having layer(s) with
a combined thickness of equal
to or more than 10 inches with
(1) Texture with no rock
fragment modifier, or (2)
texture modified by BY,
CB, GR, ST, CN, OR FL
(in the Northeast states, this
layer has 0 to 50 percent rock
fragments by weight;
texture modifiers are not used.),
or (3) CE, DE, FB, HM, MPT,
MUCK, PEAT, SP, VAR
over a layer that extends to a
depth of 60 inches or more that
has a texture (exclude COS, S, SG,
LS, FS, or LCOS) modified by BYX,
CBX, GRX, STX, CNX, or FLX or
over bedrock, CEM, or IND if
texture modified by BYX,
CBX, GRX, STX, CNX, or FLX
extends to less than 60 inches,
beginning at a depth of:
|
<20
20-40
40-60
>60 |
1
2
3
5 |
|
C. Soils in all Land Resource
Regions except W, X, and
Y having layer(s) with
a combined thickness of equal
to or more than 10 inches with
(1) Texture with no rock
fragment modifier,
over a layer that extends to a
depth of 60 inches or more that
has a texture (exclude SG, COS, S,
LS, FS, or LCOS) modified by BYV,
CBV, GRV, STV, CNV, or FLV or
over bedrock, CEM, or IND if
texture modified by BYV,
CBV, GRV, STV, CNV, or FLV
extends to less than 60 inches,
beginning at a depth of:
|
<20
20-60
>60 |
3
4
5 |
|
OR |
|
|
|
D. Soils in Land Resource
Regions W, X, and Y
having layer(s) with
a combined thickness of equal
to or more than 10 inches with
(1) Texture with no rock
fragment modifier
over a layer that extends to a
depth of 60 inches or more that
has a texture (exclude COS, S, SG,
LS, FS, or LCOS) modified by BYV,
CBV, GRV, STV, CNV, or FLV or
over bedrock, CEM, or IND if
texture modified by BYV,
CBV, GRV, STV, CNV/ or FLV
extends to less than 60 inches,
beginning at a depth of: |
<20
20-40
40-60
>60 |
1
2
3
5 |
| 10. High Gypsum |
Soils having a
gypsiferous material
layer designated as GYP
at a beginning depth of:
|
<20
20-40
40-60
>60 |
2
3
4
5 |
| 11. Organic |
A. Soils (excludes Land Resource
Regions W, X, and Y)
that are Histosols having
organic soil material; and not
lithic or limnic or terric or hydric
subgroup (e.g., Terric, Hemic Terric,
etc.), then “T” is
|
|
3 |
|
OR |
|
|
|
B. Soils that are Histosols having a
lithic, hydric, or limnic subgroup,
then “T” is
|
|
1 |
|
OR |
|
|
|
C. Soils that are Histosols having a
terric subgroup (e.g., Terric,
Hemic Terric, etc.), then “T” is
|
|
2 |
|
OR |
|
|
| |
D. Soils in Land Resource
Regions W, X, and Y
that are Histosols having
organic soil material; and not
lithic or limnic or terric or hydric
subgroup (e.g., Terric, Hemic Terric,
etc.), then “T” is
|
|
5 |
| 12. High Carbonates |
Criteria will be used after October
1, 1994.
States will need to review and possibly need to
update soil properties to generate appropriate
“T” value using Criteria A and B.
|
|
|
|
A. Soils in Land Resource Regions
B, C, D, E, W, X, and Y
having a surface layer with
equal to or less than 15 percent
calcium carbonate (CaC03)
equivalent and have a subsurface
layer with more than 25
percent (average) CaC03 equivalent
OR
having a surface layer with
more than 15 percent
calcium carbonate (CaC03)
equivalent and a
subsurface layer that
exceeds the surface layer
in calcium carbonate (CaC03)
equivalent by 20 percent or
more beginning at a depth of:
|
<20
20-40
40-60
>60 |
2
3
4
5 |
|
B. Soils (excludes Land Resource
Regions B, C, D, E, W, X, and
Y) having a surface layer
with equal to less than 15
percent calcium carbonate
(CaC03) equivalent
and have a subsurface
layer with more than 25
percent (average) CaC03 equivalent
OR
having a surface layer with
more than 15 percent
calcium carbonate (CaC03)
equivalent and a
subsurface layer that
exceeds the surface layer
in calcium carbonate (CaC03)
equivalent by 20 percent or
more beginning at a depth of:
|
<20
20-60
>60 |
3
4
5 |
| 13. Severely Eroded |
Soils designated on the
Soil Interpretations Record (SIR)
as having a severely eroded
unit modifier or have severely
eroded shown in Class Determining
Phase in Capability and Yields Per
Acre of Crops and Pasture and
have reduced productivity.
These SIR’s manually are
adjusted 1 class of “T” value
lower than the non-eroded SIR
or Class Determining Phase.
|
|
|
Texture Class, Texture Modifiers, and Terms Used in Lieu of Texture (Exhibit
618-15)
| Texture Modifiers** |
Texture Class |
Terms used in lieu of texture |
| ART - Artifactual |
C - Clay |
AM - Artifactual material |
| ARTV - Very artifactual |
CL - Clay loam |
BR - Bedrock |
| ARTX - Extremely artifactual |
COS - Coarse sand |
BY - Boulders |
| ASHY - Ashy |
COSL - Coarse sandy loam |
CB - Cobbles |
| BY - Bouldery |
FS - Fine sand |
CN - Channers |
| BYV - Very bouldery |
FSL - Fine sandy loam |
FL - Flagstones |
| BYX - Extremely bouldery |
L - Loam |
G - Gravel |
| CB - Cobbly |
LCOS - Loamy coarse sand |
HPM - Highly decomposed plant material |
| CBV - Very cobbly |
LFS - Loamy fine sand |
MAT - Material |
| CBX - Extremely cobbly |
LS - Loamy sand |
MPM - Moderately decomposed plant material |
| CEM - Cemented |
LVFS - Loamy very fine sand |
MPT - Mucky peat |
| CN - Channery |
S - Sand |
MUCK - Muck |
| CNV - Very channery |
SC - Sandy clay |
PBY - Paraboulders |
| CNX - Extremely channery |
SCL - Sandy clay loam |
PCB - Paracobbles |
| COP - Coprogenous |
SI - Silt |
PCN - Parachanners |
| DIA - Diatomaceous |
SIC - Silty clay |
PEAT - Peat |
| FL - Flaggy |
SICL - Silty clay loam |
PFL - Paraflagstones |
| FLV - Very flaggy |
SIL - Silt loam |
PG - Paragravel |
| FLX - Extremely flaggy |
SL - Sandy loam |
PST - Parastones |
| GR - Gravelly |
VFS - Very fine sand |
SPM - Slightly decomposed plant material |
| GRC - Coarse gravelly |
VFSL - Very fine sandy loam |
ST - Stones |
| GRF - Fine gravelly |
|
W - Water |
| GRM - Medium gravelly |
|
|
| GRV - Very gravelly |
|
|
| GRX - Extremely gravelly |
|
|
| GS - Grassy |
|
|
| GYP - Gypsiferous |
|
|
| HB - Herbaceous |
|
|
| HO - Highly organic |
|
|
| HYDR - Hydrous |
|
|
| MEDL - Medial |
|
|
| MK - Mucky |
|
|
| MR - Marly |
|
|
| MS - Mossy |
|
|
| PBY Parabouldery |
|
|
| PBYV - Very Parabouldery |
|
|
| PBYX - Extremely Parabouldery |
|
|
| PCB - Paracobbly |
|
|
| PCBV - Very Paracobbly |
|
|
| PCBX - Extremely Paracobbly |
|
|
| PCN - Parachannery |
|
|
| PCNV - Very Parachannery |
|
|
| PCNX - Extremely Parachannery |
|
|
| PF - Permanently frozen |
|
|
| PFL - Paraflaggy |
|
|
| PFLV - Very Paraflaggy |
|
|
| PFLX - Extremely Paraflaggy |
|
|
| PGR - Paragravelly |
|
|
| PGRV - Very Paragravelly |
|
|
| PGRX - Extremely Paragravelly |
|
|
| PST - Parastony |
|
|
| PSTV - Very Parastony |
|
|
| PSTX - Extremely Parastony |
|
|
| PT - Peaty |
|
|
| ST - Stony |
|
|
| STV - Very stony |
|
|
| STX - Extremely stony |
|
|
| WD - Woody |
|
|
** “Texture Modifiers” may apply to both the “texture class” and “terms used in lieu
of texture”. Some apply to both, others only apply to one or the other. Refer to
part 618.67.
Wind Erodibility Groups (WEG) and Index (Exhibit 618-16)
| WEG 1,3,4,5,7 |
Properties of Soil Surface Layer |
Dry Soil Aggregates More Than 0.84 mm (wt.%) |
Wind Erodibility Index (I) (tons/ac/yr) |
| 1 |
Very fine sand, fine sand, sand or coarse sand2 |
1
2
3
5
7 |
310
250
220
180
160 |
| 2 |
Loamy very fine sand, loamy fine sand, loamy sand, loamy coarse sand; very fine sandy loam and silt loam with 5 or
less percent clay and 25 or less percent very fine sand; and sapric soil materials (as defined in
Soil Taxonomy); except Folists |
10 |
134 |
| 3 |
Very fine sandy loam (but does not meet WEG criterion 2), fine sandy loam, sandy loam, coarse sandy loam; noncalcareous
silt loam that has greater than or equal to 20 to less than 50 percent very fine sand, and greater than or equal to 5 to
less than 12 percent clay. |
25 |
86 |
| 4 |
Clay, silty clay, noncalcareous clay loam that has more than 35
percent clay and noncalcareous silty clay loam that has
more than 35 percent clay. All of these do not have sesquic, parasesquic, ferritic, ferruginous, or kaolinitic mineralogy (high iron
oxide content). |
25 |
86 |
| 4L |
Calcareous6 loam, calcareous silt loam, calcareous silt, calcareous sandy clay, calcareous sandy clay loam,
calcareous clay loam and calcareous silty clay loam. |
25 |
86 |
| 5 |
Noncalcareous loam that has less than 20 percent clay; noncalcareous silt loam with greater than or equal to 5 to
less than 20 percent clay (b ut does not meet WEG criterion 3); noncalcareous sandy clay loam; noncalcareous sandy clay;
and hemic materials (as defined in Soil Taxonomy). |
40 |
56 |
| 6 |
Noncalcareous loam and silt loam that have greater than or equal to 20 percent clay; noncalcareous clay loam and
noncalcareous silty clay loam that has less than or equal to 35 percent clay; silt loam that has parasesquic, ferritic,
or kaolinitic mineralogy (high iron oxide content) |
45 |
48 |
| 7 |
Noncalcareous silt; noncalcareous silty clay, noncalcareous silty clay loam, and noncalcareous clay that have sesquic,
parasesquic, ferritic, ferruginous, or kaolinitic mineralogy (high content of iron oxide) and are Oxisols or Ultisols;
and fibric material (as defined in Soil Taxonomy) |
50 |
38 |
| 8 |
Soils not susceptible to wind erosion due to rock and pararock fragments at the surface and/or wetness; and Folists |
-- |
0 |
1 For all WEGs except sands and loamy sand textures, if percent rock and pararock fragments (>2mm) by volume is 15-35,
reduce “I” value by one group with more favorable rating. If percent rock and pararock fragments by volume is 35-60, reduce
“I” value by two favorable groups except for sands and loamy sand textures which are reduced by one group with more favorable
rating. If percent rock and pararock fragments is greater than 60, use “I” value of 0 for all textures except sands and loamy
sand textures which are reduced by three groups with more favorable ratings. An example of more favorable “I” rating is next
lower number - “I” factor of 160 to “I” factor of 134 or “I” factor of 86 to “I” factor of 56. The index values should correspond
exactly to their wind erodibility group.
2 The “I” values for WEG 1 vary from 160 for coarse sands to 310 for very fine sands. Use an “I” of 220 as an average
figure.
3 All material that meets criterion 3 in the requirements for andic soil properties in the Keys to Soil Taxonomy, 10th
edition, regardless of the fine earth texture, are placed in WEG 2.
4 All material that meets criterion 2, but not criterion 3, in the requirements for andic soil properties in the Keys to
Soil Taxonomy, 10th edition, regardless of the fine earth texture, are placed in WEG 6 except for medial classes of Cryic
Spodosols having MAAT < 40 degrees F., which are placed in WEG 2.
5 Surface layers or horizons that do not meet andic soil properties criteria but do meet Vitrandic, Vitritorrandic, and
Vitrixerandic subgroup criteria (thickness requirement excluded) move one group with less favorable rating.
6 Calcareous is a strongly or violently effervescent reaction of the fine-earth fraction to cold dilute (1N) HCL; a
paper “Computing the Wind Erodible Fraction of Soils” by D. W. Fryear et.al (1994) in the J. Soil and Water Conservation
49 (2) 183-188 raises a yet unresolved question regarding the effect of carbonates on wind erosion.
7 For soils with thin “O” horizons on mineral soils, WEG is based on the first mineral horizon.
Key Landforms and Their Susceptibility to Slippage (Exhibit
618-17)
| Topography |
Landform or Geological Materials |
Slippage PotentialA |
| I. Level Terrain |
|
|
| A. Not elevated |
Floodplain, Till plain, Lake bed |
3 |
| B. Elevated |
|
|
| 1. Uniform Tones |
Terrace, Lake bed |
2 |
| 2. Surface irregularities, sharp cliff |
Basaltic plateau |
1 |
| 3. Interbedded-porous over impervious
layers |
Lake bed, coastal plain |
1 |
| II. Hilly Terrain |
|
|
| A. Surface Drainage not well integrated |
|
|
| 1. Disconnected drainage |
Limestone |
3 |
| 2. Deranged drainage, overlapping hills,
associated with lakes and swamps (glaciated areas only) |
Moraine |
2 |
| B. Surface drainage well integrated |
|
|
| 1. Parallel ridges |
|
|
| a. Parallel drainage, dark tones |
Basaltic hills |
1 |
| b. Trellis drainage, ridge-and-valley
topography, banded hills |
Downslope tilted sedimentary rock |
1 |
| c. Pinnate drainage, vertical-sided
gullies |
Loess |
2 |
| 2. Branching ridges, hilltops at common
elevation |
|
|
| a. Pinnate drainage. vertical-sided
gullies |
Loess |
2 |
| b. Dendritic drainage |
|
|
| (1) Banding on slopes |
Flat-lying sed. rocks |
2 |
| (2) No banding on slopes |
|
|
| (a) Moderately to highly dissected
ridges, uniform slopes |
Clay Shale |
1 |
| (b) Low ridges associated with coastal
features |
Dissected coastal plains |
1 |
| (c) Winding ridges connection conical
hills, sparse vegetation |
Serpentinite |
1 |
| 3. Random ridges or hills |
|
|
| a. Dendritic drainage |
|
|
| (1) Low, rounded hills meandering streams |
Clay shale |
1 |
| (2) Winding ridges, connecting conical
hills, sparse vegetation |
Serpentinite |
1 |
| (3) Massive, uniform, rounded to A-shaped
hills |
Granite |
2 |
| (4) Bumpy topography (glaciated areas
only) |
Moraines |
2 |
| III. Level to Hilly Terrain |
|
|
| A. Steep slopes |
Talus, colluvium |
1 |
| B. Moderate to flat slopes |
Fan, delta |
3 |
| C. Hummocky slopes with scarp at head |
Old slide |
1 |
A
1 = susceptible to slippage (Unstable);
2 = susceptible to slippage under certain conditions (Moderately unstable);
3 = not susceptible to slippage except in vulnerable locations (Slightly unstable to stable).
Example Worksheets for Soil Moisture State by Month and Depth (Exhibit
618-18)
< Back to Part 618 Contents
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