“Updates of K factor, T factor, and Hydrologic Soil Groups - PowerPoint Presentation

Slide1

“Updates of K factor, T factor, and Hydrologic Soil Groupsin the Maryland Soils Database”

Presented by James BrewerResource Soil Scientist - Easton, MD

WebinarThursday Feb. 23, 20121:00 -2:00 PMSlide2

ANY QUESTIONS!!Don’t hesitate to ask!Slide3

WEBINAR OBJECTIVESNASIS – Stored vs CalculatedWhat, Where, WhyK FactorsT FactorHSG’sSidebar Discussion

RUSLE2HEL ClarificationSlide4

SOILS DATABASESlide5

SOIL PROPERTY DATA ELEMENTSOver 150 individual entries populatedMany have Low, RV, and HighSlide6

List of some properties:SOIL PROPERTY DATA ELEMENTSAvailable Water CapacityBulk Density

Cation-Exchange Capacity

Electrical ConductivityFlooding Frequency, DurationRock Fragments Horizon Depth

Slope

Liquid Limit

Organic Matter

Particle Size

Percent Passing Sieves

Ponding

Depth, Duration

,

Frequency

Reaction, Soil (pH).

Saturated Hydraulic

ConductivitySlide7

Used to generate: “Soil Property Interpretations”SOIL PROPERTY DATA ELEMENTSCorrosionDrainage Class

Engineering Classification

Excavation Difficulty ClassesPotential Frost ActionHydrologic Soil Groups

Soil

Erodibility

Factors

Soil Slippage Potential

T

Factor

Wind

Erodibility

Group

and

IndexSlide8

NASIS – Stored vs Calculated InterpretationsK Factor – Soil ErodibilityT Factor – Soil Loss ToleranceHSG - Hydrology Soil GroupsWEG – Wind Erodiblity GroupWEI – Wind Erodibiltiy IndexSteel CorrosionConcrete Corrosion.Slide9

NASIS Calculations – Based On?Better soil property data for most, if not all individual components. Both major and minor.(K factors, Corrosion Potentials)Change in criteria used to generate soil property interpretations(T factors, HSG, WEG, WEI)Slide10

WHY CALCULATE????Need to populate commonly used values (property interpretations)Can’t measure directly but can be consistently derived from other date Over entire databaseSlide11

WHY CALCULATE????Increase internal consistency in the databaseWithin map units, components, horizonsIn other words: The same “stuff” will have the same “values”Slide12

SPLASH EROSIONRAINDROPS FALLING ON EXPOSED SOIL CAN BREAK OFF SOIL PARTICLES TO BE LOST IN RUNOFF WATERSlide13

What is K factor??Measure of soil erodibility under standard unit plot condition72.6 ft long, 9% steep, tilled continuous fallow, up and down hill tillageMajor factors affecting itParticle sizes, organic matter, structure, permeability and yes rock fragmentsSlide14

SOIL ERODIBILITY - KGeneral effect of textureFine textures: (clays) resistant to detachment because of aggregationCoarse textures: (sands) easily detached, but low runoff, large, dense particles

not easily transportedMedium textures: (loams) moderately detachable, moderate to high runoff

Silts: easily detached, high runoff, small, easily transported sedimentSlide15

Two Kinds of K Factors Kf applies only to the fine-earth (less than 2.0 mm) fraction [Kf – free of rock fragments]

Kw factor applies to the whole soil,

includes rock fragments within the soil layer [Kw – with rock fragments]Slide16

Kf - Based on Wischmeier NomographSlide17

Kf and Kw Factor Classes0.02

0.05

0.100.15

0.17

0.20

0.24

0.28

0.32

0.37

0.43

0.49

0.55

0.64

Tons per acre per U.S.

erosivity

unitSlide18

Fine textures: (clays) 0.05-0.15Coarse textures: (sands) 0.05-0.20Medium textures: (loams) 0.25-0.45Silts: 0.45-0.65

Kf

and Kw Factor ClassesGeneralizationsSlide19

Convert Kf to Kw

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

.02Slide20

Where is K factor used?Maryland’s COMAR - Highly Erodible Soils (HES)NRCS RUSLE2NRCS – Highly Erodible Land (HEL)MDA – Phosphorus Site IndexSlide21

COMAR Highly Erodible Soils Found in: FOREST CONSERVATION - 08.19.03.00. AGRICULTURAL LAND PRESERVATION - 15.15.07.00. Stormwater Management Plans - 26.17.02.00. NONTIDAL WETLANDS -26.23.01.00. CRITICAL AREA - 27.01.01.00.

2011 MD Stand. And Specs. Soil Erosion and Sediment Control– Design and Construction Manual Slide22

Soils with a slope >15 % orSoils with a K value >0.35 and with slopes >5 %Kf or Kw, not sure?? COMAR HES Slide23

PICTURES SPEAKLOUDER THAN WORDSSlide24

NRCS RUSLE2RUSLE2 uses the Kf (fine-earth, rock free) factorSurface layer Kf from NASIS database via Soil Data Mart via Purdue Univ.Slide25

NRCS RUSLE2Select County and Map Unit ComponentKf loaded into equation in “background”Can’t be changed?Slide26

From MD RUSLE2 User's Guide 06/2008The soil object includes information on soil erodibility, soil texture, hydrologic soil group, and rock cover. Also, this object includes the soil erodibility to compute a value for the soil erodibility factor if one is not available.

Maybe??Slide27

Adjusting Rock Cover in RUSLE2 Slide28

Guidelines for Rock Cover in RUSLE2 Rock cover on the soil surface affect the Cover & Management factor in RUSLE2Rock cover (fragments) does not affect the

Soil Erodibility factor used in RUSLE2RUSLE2

uses the Kf (rock free) soil erodibility factor.Slide29

Guidelines for Rock Cover in RUSLE2 Using Kw would would “double account” of the effect of cropping & managementDon’t use rock cover or rock content values from soil survey data Measure in field like you do plant litter If present

and not entered in RUSLE2, erosion is over predictedSlide30

Guidelines for Rock Cover in RUSLE2 Or use table from MD RUSLE2 User's Guide 06/2008RUSLE2 Rock Fragments Defined as > 3/8 in sizeSlide31

Where to find Kf?Slide32

Lower Eastern Shore Soils K for ~35% components will increase by 1 or more classes K for ~25% components will decrease by 1 or more classes This may not have a lot of impact, as there is not much farm land

with >5% slopeGeneral trends for results of

K Calculations in MarylandSlide33

General trends for results ofK Calculations in MarylandWestern Coastal Plain and Upper Eastern Shore Soils K for ~ 20% components will increase by 1 or more classes

~ 39% are C and D

slope map units K for ~ 48% components will decrease by 1 or classes ~ 37% are C and D slope map unitsSlide34

Piedmont SoilsK for ~ 35% components will increase by 1 or more classes ~ 46% are in C and D slope map units  K for ~ 22% components

will decrease by 1 or more classes ~ 37

% are in C and D slope map units General trends for results ofK Calculations in MarylandSlide35

Mountain SoilsK for ~ 28% components will increase by 1 or more classes ~ 46% are in C and D slope map units K for ~ 45% components will decrease by

1 or more classes ~ 25% are in C and D slope

map unitsGeneral trends for results ofK Calculations in MarylandSlide36

Half WayThroughQuestionsso far?Slide37

Factors of Soil Formation: s = f' ( cl, o, r, p, t )Slide38

HEL DETERMINATIONSThree Areas of ImportanceWhen to use Frozen 1990 HEL Map unit listField visit for PHEL areas or where SS updated since 1990CRP – Different HEL DeterminationsSlide39

HEL Frozen Map Unit List - 1990Used for HEL or NHELPHEL - onsite required for determination to verify HEL or NHELSlide40

Field Visit Includes PHEL Map UnitsVerify HEL or NHEL to finialize. (maybe due to field boundary changes) New determination can be issued for specific crop field. (using Jan. 1990 K and T factor data)Slide41

Soil Survey Updated Since Jan. 1990Any new HEL map units can be appended to the Frozen ListCrop fields with previous HELC determinations will not be changed by any additions of new map units to the listSlide42

CRP – HEL Determinations (Automated System)Doesn’t use Frozen Map Unit List -1990Doesn’t use specific soils mapping of original HELUses current soils data in Toolkit (SDM)Uses average of 3 major soils in acreageSlide43

Soils with a slope >15 % orSoils with a K value >0.35 and with slopes >5 %Maryland COMAR HESHighly Erodible Soils

NRCS/FSA HEL DETERMINATIONS

Highly Erodible LandHEL Frozen Map Unit List - 1990Slide44

NOT TIME TO RELAX YET!Questions?Slide45

What is T Factor?? Soil Loss Tolerance Definition - maximum amount of erosion at which the quality of a soil as a medium for plant growth can be maintainedClasses - 1, 2, 3, 4, and 5T factors - represent the goal for maximum annual soil lossSlide46

Calculated from the soil properties and qualities. Criteria from: 1. The severity of physical or chemical properties of subsurface layers; and 2. The economic feasibility of utilizing management practices to overcome limiting layers or conditions.T Factor - Soil Loss Tolerance Slide47

19 Soil Characteristic in Criteria:OrganicBedrockFragmentalRock fragmentsFragipan Sandy substratumHigh aluminumT Factor - Soil Loss Tolerance Slide48

Piedmont/Mountain SoilsBedrockFragipan Rock fragmentsCoastal Plain SoilsSandy substratumHigh aluminum (may over ride)T Factor Calculations

Maryland Soil Property ChangesSlide49

Where is T factor used?NRCS RUSLE2NRCS – Highly Erodible Land (HEL)NRCS – Many Conservation ProgramsState Land Planning ProgramsSlide50

Lower Eastern Shore Soils T for ~4% map unit acreage will increase by 1 or more classes T for ~20% map unit acreage will decrease by 1or more classes

 General trends for results of

T Calculations in MarylandSlide51

Western Coastal Plain and Upper Eastern Shore SoilsT for ~17% map unit acreage will increase by 1 or more classes T for ~35% map unit acreage will decrease by 1or more classes

 General trends for results ofT Calculations in MarylandSlide52

Piedmont SoilsT for ~8% map unit acreage will increase by 1 or more classes T for ~10% map unit acreage will decrease by 1or more classes

 General trends for results ofT Calculations in MarylandSlide53

Mountain SoilsT for ~5% map unit acreage will increase by 1 or more classes T for ~12% map unit acreage will decrease by 1or more classes

 General trends for results ofT Calculations in MarylandSlide54

Questions?Slide55

What are Hydrology Soil Groups?? Definition - group of soils having similar runoff potential under similar storm and cover conditions Official - National Engineering Handbook, Chapter 7Classes - A, B, C, and D, and three dual classes, A/D, B/D, and C/D Slide56

Criteria - uses soil properties that influence runoff potential Soil Properties: Depth to a seasonal high water tableSaturated hydraulic conductivity (Ksat) after prolonged wetting Depth to a layer with a very slow water transmission rate. Changes in soil properties caused by land management or climate changes also cause the hydrologic soil group to change.

Hydrology Soil Groups

Slide57

General HSG Descriptions Based on all when thoroughly wetGroup A Soils - low runoff potentialGroup B Soils - moderately low runoff potential Group C – Soils moderately high runoff potential Group D – Soils high runoff potential or high water tableSlide58

General HSG Descriptions Based on all when thoroughly wetDuel Groups – used when D group soils can be adequately drained Assigned to dual hydrologic soil groups (A/D, B/D, and C/D) based on their saturated hydraulic conductivity and the water table depth when drained. The first letter applies to the drained condition and the second

to the undrained condition. Slide59

Pre Calculations: Assignment to group by general criteria guidelinesExample A group: high infiltration rate; deep; well drained to excessively drained sands or gravelsExample C group: slow infiltration rate; moderately fine to fine textureHSG’s Calculations

Maryland Soil Property ChangesSlide60

Present Calculations: Assignment to group by detailed calculation of very specific criteriaExample A group:HSG’s Calculations

Maryland Soil Property ChangesSlide61

Present Calculations: Example A group:HSG’s CalculationsMaryland Soil Property ChangesSlide62

Present Calculations for Duel Classes: Example A/D group: WT break is on 24”Our Drainage class breaks at 20”Now SWPD have duel classesHSG’s Calculations

Maryland Soil Property ChangesSlide63

HSG’s used in equations that estimate runoff from rainfall. Solving hydrologic problems in planning watershed protectionFlood prevention projects Planning & designing structures for the use, control, and disposal of water.

Hydrology Soil Groups

Where used? Slide64

Many Federal, State, and Local Engineering Land Use Management programs and practices and BMP’sRUSLE2 for use in Subsurface Drainage SystemsNRCS Waste Management Soil InterpretationsMDE - SWM and SEC Practices

Hydrology Soil Groups

Where used? Slide65

General trends for results ofHSG Calculations in MarylandCoastal Plain SoilsB to other class – 38% of components

Piedmont and Mountain Soils

D to Duel – 11% of componentsC to D – 10% of componentsC to B – 9% of componentsB to A - 8% of componentsSlide66

Questions?james.brewer@md.usda.gov410 822 1577 x 121