Soil Infiltration

8/3/2019 Soil Infiltration

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Soils Defined

Natural Body that Occurs on the LandSurface that are Characterized by One or

More of the Following:

Consists of Distinct Horizons or Layers

The ability to support rooted plants in a natural

environment

Upper Limit is Air or Shallow Water Lower Limit is Bedrock or Limit of Biological Activity

Classification based on a typical depth of 2 m or

approximately 6.0 feet


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Another Definition of Soils

A Natural 3 - Dimensional Body at the

Earth Surface

Capable of Supporting Plants

Properties are the Result of Parent Material,

Climate, Living Matter, Landscape Position

and Time.

Soil Composed of 4 Components (mineralmatter, organic matter, air, and water)


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Five Soil Formation

Factors

Organisms

Climate Time

Topography and

Landscape Setting

Parent Material

R


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Soil Food Web - Organisms

Micro &Macroscopic

Decomposition of

Organic Matter

Animals Living in

Soil

Vegetation Types

Human Activity

Redoximorphic

Feature Formation

Image Source: The University of Minnesota, 2003


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Climatic Elements

(Energy & Precipitation)

Annual and Seasonal

Rainfall Temperature Range

Biologic Production

and Activity

Weathering (Wind,

Water, and Ice)

Translocation of

Material


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Climate and Soil Development

Image Source: University of Wisconsin, 2002


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Geologic Time

Time


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Landscape and Relief

(Soil Texture)

Image Source: University of Wisconsin, 2002

A- Sandy Texture

and

Loamy Sand

B- Sandy

Textures

C- Clay Loam,Loam, Silt Loam


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Landscape and Relief

(Drainage)

Image Source: NJ NRCS, 2002

Water Movement

Soil Drainage

Landscape

Configuration

(Convex, Concave)

Elevation

Water Movement


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Parent Material

Geological Materials

Minerals and Rocks

Glacial Materials

Loess (wind blown)

Alluvial Deposits Marine Deposits

Organic Deposits

Influences

Minerals Present

Colors

Chemical Reactions

Water Movement

Soil Development

Glacial Material

Bedrock


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Soil Horizons

Layer of Soil Parallel

to Surface

Properties a function

of climate, landscapesetting, parent

material, biological

activity, and other soil

forming processes. Horizons (A, E, B, C,

R, etc)

Image Source: University of Texas, 2002


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Soil Horizons

O- Organic Horizons Organic Layers of

Decaying Plant and

Animal Tissue Aids Soil Structural

Development

Helps to Retain Moisture

Enriches Soil withNutrients

Infiltration Capacity

function of Organic

Decomposition

O Horizon

Dark in Color Because of

Humus Material - 1,000,000

bacteria per cm3


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Soil Horizons

A Horizons: Topsoil Mineral Horizon Near

Surface

Accumulation of Organic

Material

Eluviation Process Moves

Humic and Minerals from O

Horizon into A horizon

Ap - Plowed A Horizon

Ab - Buried Horizon

Soil dark in color, coarser in

texture, and high porosity

A Horizon


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Soil Horizons: E Horizons

Albic Horizon (Latin - White) Mineral Horizon Near

Surface

Movement of Silicate Clay,Iron, and Aluminum from the A

Horizon through Eluviation

Horizon does not mean a water

table is present, but the horizoncan be associated with high

water table , use Symbol Eg

(gleyed modifier)

Underlain by a B (illuvial)

horizon

E Horizon


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Soil Horizons: B Horizons

Zone of Maximum Accumulation Mineral Horizon

Illuviation is Occurring -

Movement into the Horizon

B Horizon Receives Organic andInorganic Materials from Upper

Horizons.

Color Influence by Organic, Iron,

Aluminum, and Carbonates

Bw - Weakly Colored or Structured

Bhs- Accumulation of illuvial

organic material and sesquioxides

Bs- Accumulation of sesquioxides

Bt- Translocation of silicate clay

Bx- Fragipan Horizon, brittle

Bhs Horizon

Bs Horizon

Bw Horizon


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Soil Horizons: Bx and Bt Horizons

Bx: B horizon with fragipan, a compact,

slowly permeable subsurface horizon that

is brittle when moist and hard when dry.

Prismatic soil structure, mineral coatings

and high bulk density

Horizons Indicate Reduced Infiltration

Capacity and Permeability

Bt: Clay accumulation is indicated by

finer soil textures and by clay

coating peds and lining pores

Area of Highest

Permeability

along Prism

Contact


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C- HorizonsDistinguished by Color,

Structure, and Deposition

Mineral Horizon or Layer,

excluding Rock

Little or No Soil-Forming May be Similar to

Overlying Formation

May be Called Parent

Material

Layer can be Gleyed

Developed in Place or

Deposited


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R- Horizons

Hard, Consolidated

Bedrock

Typically Underlies a

C Horizon, but could

be directly below an A

or B Horizon.RHorizon


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Soil Hydrologic Cycle

Source: Vepraskas, M.J, et. Al. Wetland Soils, 2001.


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Soil Drainage Class

and Soil GroupSoil Drainage Class - Refers to Frequencyand Duration of Periods of Saturation or Partial

Saturation During Soil Formation. There are 7

Natural Soil Drainage Classes.

Hydrologic Soil Group-Refers to SoilsRunoff Producing Characteristics as used in the

NRCS Curve Number Method. There area 4

Hydrologic Soil Groups (A, B, C, D).


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Group A and BGroup A is sand, loamy sand or sandy loam types of

soils. It has low runoff potential and high

infiltration rates even when thoroughly wetted.

Deep, well to excessively drained sands or gravels

and have a high rate of water transmission. Root

Limiting / Impermeable layers over 100 cm or 40

inches*****************

Group B is silt loam or loam. It has a moderate

infiltration rate when thoroughly wetted.

Moderately deep to deep, moderately well to well

drained soils with moderately fine to moderately

coarse textures. Root Limiting / Impermeable e

layers over 50 to 100 cm or 20 to 40 inches

Group A- Well Drained


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Group C and DGroup C soils are sandy clay loam. They have

low infiltration rates when thoroughly wettedand consist chiefly of soils with a layer that

impedes downward movement of water and

soils with moderately fine to fine structure.

Perched water table 100 to 150 cm or 40 to 60

inches; root limiting 20 to 40 inches.

*****************

Group D soils are clay loam, silty clay loam,

sandy clay, silty clay or clay. They have very

low infiltration rates when thoroughly wetted

and consist chiefly of clay soils with a high

swelling potential, soils with a permanent highwater table, soils with a claypan or clay layer at

or near the surface and shallow soils

over nearly impervious material ( < 20 inches).

Group D - Poorly Drained

Highest Runoff Potential


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Definitions

Infiltration - The downward entry of water into the immediate

surface of soil or other materials.

Infiltration Capacity- The maximum rate at which water can

infiltrate into a soil under a given set of conditions.

Infiltration Rate- The rate at which water penetrates the surface of

the soil and expressed in cm/hr, mm/hr, or inches/hr. The rate of

infiltration is limited by the capacity of the soil and rate at which

water is applied to the surface. This is a volume flux of water

flowing into the profile per unit of soil surface area (expressed asvelocity).

Percolation -Vertical and Lateral Movement of water through the

soil by gravity.


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Infiltration Rate and Capacity

Soil Factors that Control Infiltration Rate:

- Vegetative Cover, Root Development and Organic Content

- Moisture Content

- Soil Texture and Structure- Porosity and Permeability

- Soil Bulk Density and Compaction

- Slope, Landscape Position, Topography


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Infiltration Rate (Time Dependent)

Decreasing Infiltration

Infiltration with Time Rate is Initially

High Because of a Combination of

Capillary and Gravity Forces

Final Infiltration Capacity

(Equilibrium)- Infiltration

Approaches Saturated

Permeability

Steady GravityInduced Rate


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Infiltration Rate (Moisture)Infiltration Decreases with Time

1) Changes in Surface and Subsurface Conditions

2) Change in Matrix Potential

3) Overtime - Matrix Potential Decreases and Gravity Forces

Dominate - Causing a Reduction in the Infiltration Rate


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Measuring Infiltration Rate

Flooding (ring) Infiltrometers

Single ring

Double ring

Flooded Infiltrometers

Tension Infiltrometers

Rainfall-Runoff Plot Infiltrometers


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Measuring Infiltration Rate


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Single Rings Infiltrometers

Cylinder - 30 cm in Diameter

Drive 5 cm or more into Soil Surface or Horizon

Water is Ponded Above the Surface

Record Volume of Water Added with Time to Maintain a

Constant Head

Measures a Combination of Horizontal and Vertical Flow


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Double Rings Infiltrometers

Outer Rings are 6 to 24 inches in Diameter (ASTM - 12 to 24 inches)

Mariotte Bottles Can be Used to Maintain Constant Head

Rings Driven - 5 cm to 6 inches in the Soil and if necessary sealed


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Other Infiltrometers

Ponded InfiltrometersTension Infiltrometer

Unsaturated Flow Of Water


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Infiltration Rate by

Soil Group/ Texture

Source: Texas Council of Governments, 2003.


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Infiltration Rate

Function of Slope & Texture

Source: Rainbird Corporation, derived from USDA Data


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Infiltration Rate

Function of Vegetation

Source: Gray, D., Principles of Hydrology, 1973.


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Comparison Infiltration to

Percolation Testing

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

1 2 3 4 5 6 7 8 9 10

Trail

Rate(in/hr)

Infiltraton Test

Percolation Test

Percolation

Testing

Over

EstimatedInfiltration

Rate by 40

to over

400%

Source: On-site Soils Testing Data, (Oram, B., 2003)


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0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Rate

(in/hr)

Infiltration Rock Content < 20 %

Infiltration Rock Content > 60 %

Infiltration and Rock Content (Oram, B. 2003)

fil i


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Infiltration

(Compaction/ Moisture Level)


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Case 1 :Myers Proposed Development

Worcester Township, Pennsylvania

Abbottstown Silt Loam,Deep to Moderately Deep, Somewhat Poorly Drained

Some Areas Shallow Depth to Firm Bedrock

Signs of Erosion

Low Surface and Near Surface Infiltration Rates

Associated with Surface Smearing, Btx, Bx Horizons

BC/ C /R Horizons Higher Infiltration Rate.

Readington Silt Loam

Deep Moderately Well Drained

Low Infiltration Surface, Bd, and Btx

High Infiltration in C and R Horizons

I filt ti R t


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Infiltration Rate

Function of Horizon A, B, Btx, Bt, C, R

C/R Testing - Areas Fractured Rock

Source: On-site Infiltration Testing - Mr. Brian Oram, PG (2003)


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Case 2: Country View at Salford

Salford Township, Montgomery County, PA

Soil CrB2 Croton Silt Loam

Deep, Poorly Drained

Diagnostic Features: Bx, Bxg, Bt, R (firm)

Reported Infiltration Rate: < 0.2 to 2.0 in/hr

Field Measured Rate: 0.1 to 0.52 in/hr

Primary Natural Drainage:

Depression Storage, Swale Development, Throughflow

Flow Through Wetland Areas, Overland Flow

Predevelopment Conditions:

Unstable Stream Banks, Overland Flow from Off Site


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Evaluation InfiltrationStep 1: Desktop Assessment - GIS

Review Published Data Related to Soils, Geology, Hydrology

Step 2: Characterize theHydrological Setting

Where are the Discharge and Recharge Zones?

What forms of Natural Infiltration or Depression Storage Occurs?

Step 3: On-Site Assessment

Deep Soil Testing Throughout Site Based on Soils and Geological Data

Double Ring Infiltration Testing

How will water move through the site ?

Step 4: Engineering Review and Evaluation

Step 5: Additional Infiltration or On-site Testing

Step 6: Final Design


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Soils, Infiltration,

and On-site TestingPresented by:

Mr. Brian Oram, PG, PASEO

Wilkes University

GeoEnvironmental Sciences and

Environmental Engineering Department

Wilkes - Barre, PA 18766

570-408-4619

http://www.water-research.net


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Horton Equation (1939)

Infiltration is a Function of Time as defined by:

f(t) = fc + (fo fc)e^-kt

f(t) = infiltration rate for any time t from beginning of infiltration

fc = infiltration capacity

fo = initial infiltration rate at (t=0)

e = 2.71 =base of natural log

kis a measure of the rate of decrease in infiltration rate(constant that depends on soil type)

Large Watershed Application - Replaced by Philip and Green-Ampt

Horton Method Used in EPA Storm Water Management Model


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Green-Ampt Equation Green-Ampt model was the first physically-based model/equation describing

the infiltration of water into soil. The model yields cumulative infiltration andthe infiltration rate as an implicit function of time. The volume of infiltration

was a function of:

Soil pores are saturated behind wetting front;

Wetting front moves in response to capillary forces; and

Darcys flow governs that headloss in the saturated zone.

Approx. Equation: f = (A/F)+B; f = infiltration rate, F -

accumulative infiltration, and A and B are fitted parameters

The Green-Ampt Model has been modified to calculate water

infiltration into non-uniform soils by several researchers . In 1989,GALAYER was developed for heterogenous soils

Models Available at:

http://www.epa.gov/ada/csmos/ninflmod.html

http://www.bae.ncsu.edu/soil_water/drainmod/dmversions.htm


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Philip Equation (1960)

where:

F = total depth of infiltrated water in mm.

t = time in seconds K = hydraulic conductivity in mm/secm = the average moisture content of the soil to the depth of the wetting front

m--0 = initial soil moisture content - based on API calculation or input

Pot = capillary potential at the wetting front in mm

Pot = 250 log (K) + 100

D1 = depth of water on the soil surface

Takes into account the Ponding Head

Models Available at:

http://www.epa.gov/ada/csmos/ninflmod.html


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Soils, Infiltration,

and On-site Testing

Presented by:

Mr. Brian Oram, PG, PASEO

Wilkes University

GeoEnvironmental Sciences and

Environmental Engineering DepartmentWilkes - Barre, PA 18766

http://www.water-research.net

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