Site Characteristics

Location: Latitude and longitude or other standard system; Township, range, section; meets and bounds. From map or Geo-positioning system (GPS).

Climate: Temperature (annual and seasonal), rainfall (annual and distribution), potential evapotranspiration; impact on soil use and soil development

Vegetation: type, species, etc. Describe in as much detail as possible. Historic vegetation impact on soil development

Land Use: cropland, forest land, rangeland, etc.

Physiographic province: Piedmont, Coastal Plain, Ridge and Valley, etc

Landscape: slope gradient, slope shape, aspect, land form, landscape postionParent material: type, relation to landscape

GA Major Land Resource Areas (MLRA)

Geomorphic Surface

floodplain (natural levee or back swamp) low terracehigh terraceupland dunealluvial fanmoraine many others Floodplain Terraces Upland

Geomorphic Position

headslope, noseslope, sideslopeconvergent slopes collect runoff and shallow subsurface flow, i.e. wetter parts of the landscapedivergent slopes shed runoff and shallow subsurface flow, i.e. drier parts of the landscape.

Site Characteristics - Slope

Percent (or degrees)Shape - both parallel and perpendicular to contours - convex, plane, or concave

impacts land stability, runoff and erosion, and hydrology

Aspect - compass point or degreesimpacts temperature and associated ET

cooler, wetter soils on north and east facing slopes

Hillslope Position

In humid climates, hillslopes are normally recognized to have 5 components, summit, shoulder, backslope, footslope, and toeslope.

Hydrology, soil development, erosion, and parent material are often affected by hillslope position. Summit – most stable position; may be wet (flat) or dry (convex) Shoulder – convex position; most erosive, dry, least developed soils Backslope – more stable than shoulder?; upper part dry; lower part wet Footslope – concave position; may have colluvial parent material; wet soils Toeslope – commonly alluvial parent materials; often wet soils (same as “bottom”)

Summit Shoulder

Backslope

Footslope Toeslope

Summit Shoulder

Backslope

Footslope Toeslope

Parent Material

Residuum Transported Alluvium Marine sediments Lacustrine deposits Volcanic ash Loess Eolian sand Glacial drift (till, outwash, various landforms) Colluvium Organic (peat, muck)

Tetonic Landscapes All continents are part of crustal plates and have two common

components: Cratons - expansive, stable regions of low relief typically in the central

part of the continent Stable is key word – little uplift or metamorphism Old soils on old landscapes Glaciation creates new younger landscapes

Folded linear mountain belts - common on the margins of continents Occurrence related to current or past collisions of plates Rocks are typically extensively metamorphosed with intrusions of igneous

rocks Relief is high High rates of erosion prevent development of very mature soils

Craton: stable

continental core

Orogenic belt: margin

subject to tectonic

forces (mt-building)

Coastal plain: transient

zone of deposition

Generalized geology

of the eastern

continental margin

Residual Parent Materials

-- Mineral composition of rock has major effect on rate, degree, and end result (soil properties) during weathering

> “mafic” vs. “felsic” igneous rocks: large effect of soil development

(clay content and mineralogy, permeability, leaching, etc.)

> sandstone vs. shale: coarse vs. fine textured soils

-- Permeability/porosity of rock also a factor

> fractured vs. intact rock (meta vs. intrusives in Piedmont)

> limestone (porous) vs. shales (laminar, rel. impermeable)

Fluvial Landforms Channel deposits

Coarse grained

Overbank deposits Texture varies across the floodplain

Both mineralogy and particle size of deposits depend on properties of the material in the watershed

Stream Terraces

Highest elevation terrace is the oldest and the terraces become progressively younger as elevation decreases.

Country RockAlluvial Fill

Floodplain

Country RockAlluvial Fill

Floodplain

Country Rock Alluvial Fill

Floodplain

Terrace 1Terrace 1

Terrace 1Terrace 2

Terrace 1

Country RockAlluvial Fill

Floodplain

Country RockAlluvial Fill

Floodplain

Country Rock Alluvial Fill

Floodplain

Terrace 1Terrace 1

Terrace 1Terrace 2

Terrace 1

Glacial Landforms Climate change is the rule rather than the exception Continental glaciers that covered much of the high latitude regions of

the earth during ice ages Sculpted most of the landforms in these areas Drive wide variations in sea level (low during Ice Ages) Wide variety of landforms, and glacial deposits widely variable Outwash: water-sorted, deposited during melt (glacial retreat) Till - material pushed, churned, and modified under the glacial ice

Poorly sorted with particle sizes that range from clay to boulders Composition depends on what was present in the path of the glacier

Limit of Glaciation in North America

Loess Silty aeolian materials Seasonal changes in amount of meltwater from glaciers results in broad

floodplains covered with fresh sediment and no vegetation Sediment was entrained by wind and deposited in the adjacent uplands

Eolian sand near floodplain Silt and clay farther away

Loess deposits are extensive and blankets existing landforms Thickness decreases with distance away from the river source Age of soils on loess and other glacial landforms about same age as

deposits ~ 12,000 ybp

Loess

Marine Deposits Deposits actually deposited at the sea-land interface Typically low relief with unconsolidated sedimentary materials

Variety of coastal environments including: Beaches, dunes: graded, bedded sands Marshes: fine clayey deposits Channel deposits and deltas: mixed sands and gravels Off-shore deposits: layered silty/clayey deposits; limestone (reefs)

Great fluctuation in sea level over geologic history Transgression/regression deposits: layers of varying composition Particle size and composition of sediments vary with the environment

in which they were deposited Mineralogy is strongly influenced by the mineralogy of the soils and

sediments in the watersheds of the streams

SEDIMENT CHARACTERISTICS AS FUNCTION OF DEPOSITIONAL ENVIRONMENT

Limestone Deposits Calcite (CaCO3) or dolomite (CaMg(CO3)2) Precipitated by marine organisms on continental shelf some distance

from the shoreline Minimal amount of silicate minerals As limestone weathers, the calcite and dolomite dissolve and are

leached from the soil Limestone derived soils are formed from the non-carbonate residues

Often clayey Humid regions – soils often clayey and red Arid and semi-arid regions – accumulations of calcium carbonate in

the subsoil because of incomplete leaching

GA Major Land Resource Areas (MLRA)

SOIL INTERPRETATIONS

--INFERENCES about derived properties, capabilities, and potential uses of a given soil based on profile and landscape properties

Derived properties:> saturated hydraulic conductivity (water flow)> available water holding capacity> infiltration rates, erodibility

Capabilities/Potential Uses:> agriculture, crop production, forestry> urban land use: construction, roads, on-site waste

water disposal (septics)

SLOPE GRADIENT

-- major determinant for many uses

-- slope classes Ag use Capabililty class

0-2% nearly level unrestricted I2-6% gently rolling some restrictions II6-10% moderately rolling mod. restrictions III10-15% steeply rolling severe restrictions IV15-25% steep ---no ag use--- V>25% really steep ---no ag use--- VI

-- slope affects urban land use also, but less severely…

AVAILABLE WATER HOLDING CAPACITY

--based on rooting depth (depth to Cr, Cd, cemented or R horizon), or to 150 cm; --water holding of each horizon in rooting zone, based on TEXTURE

cm H2O/cm soilTextural classes: sil, si, sicl: 0.2

All Other Textures 0.15s, ls 0.05

 Procedure: 1) add up depths of horizons that have textures in the THREE groups

2) correct for gravel %3) for each group, multiply by the AW per cm soil 4) sum up for each group, and rate the profile according to:

 Very Low: ≤ 7.5 cmLow: >7.5 - 15 cmModerate: >15 - 22.5 cmHigh: > 22.5

 

equivalentdepth thickness fragments thickness texture cm/cm total cm

0-20 20 5 19 sil 0.2 3.80

20-35 15 20 12 sicl 0.2 2.40

35-75 40 0 40 c 0.15 6.00

75-120 45 10 40.5 cl 0.15 6.08

120-180 60 10 54 ls 0.05 2.70

TOTAL 20.98

EXAMPLE CALCULATION FOR SOIL PROFILE:

Water Flow Rates

-- Saturated hydraulic conductivity can be estimated from field evaluated morphological properties, based on most limiting layer in entire profile

LOW: 1. fragipan in profile; OR2. at least one horizon with sc, c, and sic texture with massive, weak or platy structure

AND some ≤2 chroma colors in horizon; OR3. ≤2 chroma colors occurring directly above a Cr or R horizon

 HIGH: s and ls texture throughout profile

MODERATE: all other profiles

-- Engineering and septic uses depend upon Ksat

--can be measure in field; extremely variable property…

0.47

1.82

5.78

0.08

0.63

0.16

0.16

1.11

0.08

0.06

0.32

0.40

0.28

0.08

1.08

0.68

1.39

0.05

1.03

0.40

0.13

0 5 m

Ks, cm/h

Estimates of Ks for given soil horizon

Ks is a function of pore size distribution and tortuosity.

Pores in the soil can be grouped into three types: Packing pores

Formed by packing of particles Size depends on particle-size distribution

Intraped pores Formed by packing of soil structural units (peds) Size and abundance depend on degree of structure formation and

other structural properties Biopores

Formed by activity of flora and fauna in the soil

0.002 mm

Clay

2 mm

Sand

10 mm 10 mm

Estimates of Ks Based On:

Texture Analog for size distribution of packing pores

Structure Greatest effect for unstructured non-sandy soils and strongly

structured clayey soils Shape may also have an impact

Consistence Firmer consistence indicates binding at grain contacts Cementation that partially fills pores

Clay mineralogy (shrink swell) Difficult to estimate in the field Rely on accessory properties and tendency for mineralogy to be

similar within regions

Structure Effect on Ks

Horizon Depth Structure Clay Ks

cm % Cm/h

Bt1 20-46 2sbk 48 2.3

Bt3 79-112 2sbk 43 0.5

BC 185-194 1sbk 33 <0.1

C 269-328 0 6 1.6

Soil Wetness Class

Reflects the rate at which water is removed from the soil by both runoff and percolation. Influenced by climate, slope, hydraulic conductivity, and landscape position.

Wetness class is inferred from presence of matrix or redox depletions with value of 5 or more and chroma of 2 or less

Wetness Class Depth to chroma 2 color

cm

1 >150

2 100-150

3 50-100

4 25-50

5 <25

Soil Drainage Class

Related to soil wetness class and is more commonly used. Better referred to as “Agricultural Drainage Classes” Definitions are not rigid

Excessively drained Somewhat excessively drained Well drained Moderately well drained Somewhat poorly drained Poorly drained Very poorly drained

Seasonal Saturation

Seasonal saturation has a major impact on soil behavior and appropriate use of soil for many applications Induces anaerobic conditions which may impact growth and survival

of crops as well as native plant species Major implication of seasonal saturation for urban interpretations is

that you “cannot put more water into a full bucket If subsoil horizons are saturated and there is sufficient gradient, there

is a potential that the water in the soil and added wastewater will move downslope

May also provide a direct linkage to deeper groundwater aquifers.

Water Table Measurement

Relatively simple to measure with wells or piezometers Because of annual and seasonal water table fluctuation,

need multiple years of measurement

Water Table Measurement

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

Apr-94 Aug-94 Nov-94 Feb-95 May-95 Sep-95 Dec-95 Mar-96 Jul-96 Oct-96

Wa

ter

Ta

ble

De

pth

, fe

et

Upslope

Depression

Interpretation of Seasonal Saturation

Accurate measurement of water table heights is time consuming and expensive

Redoximorphic features used as indicators of horizons that are seasonally saturated Munsell chroma 2.

No information on duration or season of saturation A few studies have developed relationships between

redox features and duration of saturation Limited geographic extrapolation.

Relation of Seasonal Saturation to Redox Features

Feature Percent of

Time Saturated

None 4

Redox concentations 20

Redox depletions 42

Dominant gray color 51

Interpretations for Specific Uses

Based on morphological and other properties of the soil If soil properties and the impact of the properties on the use are

understood, any use interpretation can be made from basic properties.

The key is understanding how the soil impacts the use.

Property Slight Moderate Severe

Dwellings without Basements

Flooding none - any flooding

Depth to high water table (cm) >75 45-75 <45

Shrink-swell potential low moderate high

Slope (%) <8 8-15 >15

Depth to hard bedrock (m) >1.5 1-1.5 <1

Depth to cemented horizons (m) >1 0.5-1 <0.5

Cobbles and stones (volume %); weighted average of 25-100 cm depth

<30 30-65 >65

Dwellings with Basements

Flooding none - any flooding

Depth to high water table (cm) >150 75-150 <75

Shrink-swell potential low moderate high

Slope (%) <8 8-15 >15

Depth to hard bedrock (m) >1.8 1-1.8 <1

Depth to cemented horizons (m) >1 0.5-1 <0.5

Cobbles and stones (volume %); weighted average of 25-100 cm depth

<30 30-65 >65

Soils and Geomorphology - Definitions

Geomorphology (geo(Greek) = earth; morphos = form): the science that studies the properties and evolution of the earth's surface. the landscape is viewed as an assemblage of landforms which are individually

transformed by geomorphic processes. because soils are an integral part of landforms and landscapes, processes

occurring on the landscape have implications for soil development. Conversely, soil processes can be considered to be a part of landscape evolution.

Landscape: the portion of the land surface that the eye can comprehend in a single view.

Landforms: distinctive geometric configurations of the earth's land surface; features of the earth that together comprise the land surface

Soils and Geomorphology – Definitions (con’t)

Geomorphic surface: a part of the surface of the land that has definite geographic boundaries and is formed by one or more agents during a given time span. It should be considered as a surface, i.e. similar to a plane, no thickness (z) - only

x and y dimensions. Because it is formed during a specific time it is datable, either by absolute or relative means.

Erosion surface: a land surface shaped by the action of ice, wind, and water; a land surface shaped by the action of erosion.

Constructional (depositional) surface: a land surface owing its character to the process of upbuilding, such as accumulation by deposition (either fluvial or colluvial).

Geomorphic Principles

Geomorphology important in two areas (1) age, properties, and development rate of soils and

(2) hydrologic patterns on landscapes including soil effects on water re-distribution across the landscape.

Soil age: Soil development does not commence until the erosion or deposition rate has

reached a steady state that is less than the rate of soil formation. For depositional surfaces, soil age is similar to the age of deposit.

radiocarbon or other dating methods of the deposit are useful for determining soil age.

This is not true for erosional surfaces. There may have been multiple erosion episodes since the material was deposited or

exposed at the surface. Often the best age that can be derived is a relative age of the surface compared to other

geomorphic surfaces in the area.

Law of Superposition

Younger beds occur on older beds if they have not been overturned

Bed 1

Bed 2

Bed 1

Bed 2

Bed 2

Bed 1

Bed 1

2

34

2

3

2

Bed 1

Bed 2

Bed 1

Bed 2

Bed 1

Bed 2

Bed 2

Bed 1

Bed 1

Bed 2

Bed 1

Bed 2

Bed 2

Bed 1

Bed 2

Bed 1

Bed 1

2

34

2

3

2

Bed 1

2

34

2

3

2

A

B D

C

Relative Age of Erosional Surfaces

An erosional surface is: younger than the youngest material it cuts younger than any structure it bevels younger than fossils beneath the surface is the same age or older than terrestrial

deposits lying on it older than the valleys which have been cut

below it younger than materials forming an erosion

remnant above it older than deposits in the valley below it younger than any adjacent surface which

stands at a higher level older than any adjacent surface which stands

at a lower level A hillslope is the same age as the alluvial

valley fill to which it descends but is younger than the higher surface to which it ascends.

DepositionalSurface A

Erosion Surface B

DepositionalSurface A

Erosion Surface B

DepositionalSurface A

Erosion Surface C

Erosional Element,Surface B Depositonal Element,

Surface BBed 1

Bed 2 Bed 3

DepositionalSurface A

Erosion Surface C

Erosional Element,Surface B Depositonal Element,

Surface BBed 1

Bed 2 Bed 3

Hillslope Development Most upland landscapes have been sculpted by

continual erosion and removal of material by streams. Landscape development by erosion can be considered

to be cyclic and progresses through various stages; youth, maturity, and old age over time.

Davis, Penck models: assume uniform, gradual development of valley development, landscape downcutting over time.

Davis’ Stages of Hillslope Development

YouthfulBeginning

Mature Old

Davis’s Stages of Landscape Development

YouthfulBeginning

Mature Old

Davis’s Stages of Landscape Development

Implications of Davis’ Theory In mature or normal landscapes, surficial material was being removed

at a slow but constant rate Superposed on the rate of loss of surface material was a rate of soil

formation The landscape was considered to be in “equilibrium”

relative rates of downwaring and soil development determined the characteristics of the soil

the soil developed on the landscape would have the same characteristics over long periods of time

Soils thought to be in this equilibrium were considered to be “normal”

Downwaring of Hillslopes – Davis (1890)

Downwasting (Davis)T1

T3T4

T2

Downwasting (Davis)T1

T3T4

T2

Backwasting (Parallel Slope Retreat) (Penck, 1920’s)

Parallel Slope Retreat (Penck)

T1 T3T4 T5T2

Parallel Slope Retreat (Penck)

T1 T3T4 T5T2

Modern Concepts in Geomorphology: Process-based

“Dynamic equilibrium” –downwasting and uplifting forces, change over time

Erosional/Depositional Processes:Fluvial: channel incision, sediment transport/deposition/export from landscapeAeolian: erosion/deposition via wind processesHillslope: soil creep, mass wasting, landslidesWeathering: mass loss, selective dissolution, mineral transformations

Regional Processes:Glacial: reshapes whole landscapes; affects sea levelsVolcanic: mt building; source of new topography, parent materialTectonic: continental changes over geologic time; uplift, mt building, etc

Climatic Factors:Precip., temperature affect MOST other processesClimate changes OFTEN over geologic time

Landscape must RE-adjust to new climate conditions

Hillslope Position

In humid climates, hillslopes are normally recognized to have 5 components, summit, shoulder, backslope, footslope, and toeslope.

Hydrology, soil development, erosion, and parent material are often affected by hillslope position. Summit – most stable position; may be wet (flat) or dry (convex) Shoulder – convex position; most erosive, dry, least developed soils Backslope – more stable than shoulder?; upper part dry; lower part wet Footslope – concave position; may have colluvial parent material; wet soils Toeslope – commonly alluvial parent materials; often wet soils

Summit Shoulder

Backslope

Footslope Toeslope

Summit Shoulder

Backslope

Footslope Toeslope

Hydrology and Geomorphology

Movement of water and solutes across a landscape depends on geomorphic and stratigraphic relationships including landscape distribution of soil horizons

Water runs downhill Across surface In the shallow subsurface, especially if soil has water-restrictive

horizons Darcy’s law

J = Q/A = Ks(dh/L)

Most commonly applied to vertical flow through soils Also applicable to lateral water flow across the landscape

Hydrology and Geomorphology

In rolling landscapes with convex hillslope summits, soils on the lower part of the hillslope will be wetter than soils higher in the landscape

In the landscapes with the low relief and broad interfluves, little gradient to move water laterally to streams Soils in the central part of the interfluve have high seasonal water

tables and are often poorly drained Near streams, gradient for lateral movement of water is greater and

the soils are better drained “Dry Edge“ or “Red Edge” effect

As interfluve narrows, proportion of landscape that is “edge” increases End product is rolling landscape with convex summits

Darcy’s Law and Lateral Water Movement

J = Ks(dh/L)

J = (20 cm/d) X (9.9 m/100 m) = 1.98 cm/d

J = (20 cm/d) X (0.1 m/10 m) = 0.2 cm/d

100 m

10 m

1000 m 100 m

3 m

J = (20 cm/d) X (0.5 m/1000 m) = 0.01 cm/d

J = (20 cm/d) X (2.5 m/100 m) = 0.5 cm/d

“Dry edge”

Water “stacks up”

= wetter soilsWell drained soils

10 m

-3

-2

-1

0

0 1 2 3

Distance, km

Wat

er T

able

Dep

th, m

Seasonal High Water Table

Seasonal Low Water Table

Dry Edge Effect Broad Interfluve

-3

-2

-1

0

0 1 2 3

Distance, km

Wat

er T

able

Dep

th, m

Seasonal High Water Table

Seasonal Low Water Table

Dry Edge Effect Broad Interfluve

Hydrology and Geomorphology

Depth to seasonal water table effects properties in addition to color E horizon thickness Bt clay content E clay content Mineralogy

Impact on water movement through the soil High water table = limited leaching Well drained = maximum leaching

0

50

100

150

200

0 50 100 150 200 250

Depth to High Water Table

Hydrology and Geomorphology

Landscape configuration and distribution of soil horizons influence paths for movement of water and solutes in the subsurface

5 factors that influence soil development Climate Relief Biology (mostly vegetation) Parent material Time)

Parent material and relief have the greatest impact at a local scale Stratigraphy, geomorphology, their relationship to each other and

landscape hydrology