Updates of K factor T factor and Hydrologic

“Updates of K factor, T factor, and Hydrologic Soil Groups in the Maryland Soils Database” Webinar Thursday Feb. 23, 2012 1: 00 -2: 00 PM Presented by James Brewer Resource Soil Scientist - Easton, MD

ANY QUESTIONS!! Don’t hesitate to ask!

WEBINAR OBJECTIVES • NASIS – Stored vs Calculated • What, Where, Why • K Factors • T Factor • HSG’s • Sidebar Discussion • RUSLE 2 • HEL Clarification

SOILS DATABASE

SOIL PROPERTY DATA ELEMENTS • Over 150 individual entries populated • Many have Low, RV, and High

SOIL PROPERTY DATA ELEMENTS List of some properties: • Available Water Capacity • Bulk Density • Cation-Exchange Capacity • Electrical Conductivity • Flooding Frequency, Duration • Rock Fragments • Horizon Depth • Slope • Liquid Limit • Organic Matter • Particle Size • Percent Passing Sieves • Ponding Depth, Duration , Frequency • Reaction, Soil (p. H). • Saturated Hydraulic Conductivity

SOIL PROPERTY DATA ELEMENTS Used to generate: “Soil Property Interpretations” • Corrosion • Drainage Class • Engineering Classification • Excavation Difficulty Classes • Potential Frost Action • Hydrologic Soil Groups • Soil Erodibility Factors • Soil Slippage Potential • T Factor • Wind Erodibility Group and Index

NASIS – Stored vs Calculated Interpretations • • K Factor – Soil Erodibility T Factor – Soil Loss Tolerance HSG - Hydrology Soil Groups WEG – Wind Erodiblity Group WEI – Wind Erodibiltiy Index Steel Corrosion Concrete Corrosion.

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, WEI)

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

WHY CALCULATE? ? • Increase internal consistency in the database v. Within map units, components, horizons v. In other words: The same “stuff” will have the same “values”

SPLASH EROSION RAINDROPS FALLING ON EXPOSED SOIL CAN BREAK OFF SOIL PARTICLES TO BE LOST IN RUNOFF WATER

What is K factor? ? • Measure of soil erodibility under standard unit plot condition – 72. 6 ft long, 9% steep, tilled continuous fallow, up and down hill tillage • Major factors affecting it – Particle sizes, organic matter, structure, permeability and yes rock fragments

SOIL ERODIBILITY - K • General effect of texture – Fine textures: (clays) resistant to detachment because of aggregation – Coarse textures: (sands) easily detached, but low runoff, large, dense particles not easily transported – Medium textures: (loams) moderately detachable, moderate to high runoff – Silts: easily detached, high runoff, small, easily transported sediment

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]

Kf - Based on Wischmeier Nomograph

Kf and Kw Factor Classes Tons per acre per U. S. erosivity unit 0. 02 0. 10 0. 17 0. 24 0. 32 0. 43 0. 55 0. 05 0. 15 0. 20 0. 28 0. 37 0. 49 0. 64

Kf and Kw Factor Classes Generalizations – Fine textures: (clays) 0. 05 -0. 15 – Coarse textures: (sands) 0. 05 -0. 20 – Medium textures: (loams) 0. 25 -0. 45 – Silts: 0. 45 -0. 65

Convert Kf to Kw Kf value classes of less than 2 mm soil fraction. 20. 24. 28. 32. 37. 43. 49. 55 Fragment vol. % Mulch factor 1/ . 10 . 15 5 10 15 20 25 . 90. 77. 68. 61. 54 . 09. 08. 07. 06. 05 . 14. 12. 10. 09. 08 . 18. 15. 14. 12. 11 . 22. 18. 16. 15. 13 . 25. 22. 19. 17. 15 . 29. 25. 22. 20. 17 . 33. 28. 25. 23. 20 . 39. 33. 29. 26. 23 . 44. 38. 33. 30. 26 . 50. 42. 37. 30 . 58. 49. 43. 39. 35 30 35 40 45 50 . 48. 43. 38. 34. 30 . 05. 04. 03 . 07. 06. 05 . 10. 09. 08. 07. 06 . 12. 10. 09. 08. 07 . 13. 12. 11. 10. 08 . 15. 14. 12. 11. 10 . 18. 16. 14. 13. 11 . 21 18. 16. 15. 13 . 24. 21. 19. 17. 15 . 26. 24. 21. 19. 17 . 31. 28. 24. 22. 19 55 60 65 70 75 . 26. 22. 19. 16. 13 . 03. 02. 02. 01 . 04. 03. 02 . 05. 04. 03 . 06. 05. 04 . 07. 06. 05. 04 . 08. 07. 06. 05. 04 . 09. 08. 07. 06. 04 . 11. 09. 08. 07. 06 . 13. 11. 09. 08. 06 . 12. 10. 09. 07 . 14. 12. 10. 08 80 85 90 95 100 . 10. 08. 06. 04. 03 . 01. 01. 01 . 02. 02. 01. 01. 01 . 02. 01. 01 . 03. 02. 01 . 04. 03. 02. 01 . 05. 04. 03. 02. 02 . 06. 05. 04. 03. 02 . 64

Where is K factor used? • Maryland’s COMAR - Highly Erodible Soils (HES) • NRCS RUSLE 2 • NRCS – Highly Erodible Land (HEL) • MDA – Phosphorus Site Index

COMAR Highly Erodible Soils Found in: • FOREST CONSERVATION - 08. 19. 03. 00. • AGRICULTURAL LAND PRESERVATION - 15. 07. 00. • STORMWATER MANAGEMENT PLANS - 26. 17. 02. 00. • NONTIDAL WETLANDS -26. 23. 01. 00. • CRITICAL AREA - 27. 01. 00. • 2011 MD Stand. And Specs. Soil Erosion and Sediment Control– Design and Construction Manual

COMAR HES • Soils with a slope >15 % or • Soils with a K value >0. 35 and with slopes >5 % • Kf or Kw, not sure? ?

PICTURES SPEAK LOUDER THAN WORDS

NRCS RUSLE 2 • RUSLE 2 uses the Kf (fine-earth, rock free) factor • Surface layer Kf from NASIS database via Soil Data Mart via Purdue Univ.

NRCS RUSLE 2 • Select County and Map Unit Component • Kf loaded into equation in “background” • Can’t be changed?

From MD RUSLE 2 User's Guide 06/2008 • The 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? ?

Adjusting Rock Cover in RUSLE 2

Guidelines for Rock Cover in RUSLE 2 • Rock cover on the soil surface affect the Cover & Management factor in RUSLE 2 • Rock cover (fragments) does not affect the Soil Erodibility factor used in RUSLE 2 • RUSLE 2 uses the Kf (rock free) soil erodibility factor.

Guidelines for Rock Cover in RUSLE 2 • Using Kw would “double account” of the effect of cropping & management • Don’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 RUSLE 2, erosion is over predicted

Guidelines for Rock Cover in RUSLE 2 Or use table from MD RUSLE 2 User's Guide 06/2008 • RUSLE 2 Rock Fragments Defined as > 3/8 in size

Where to find Kf?

General trends for results of K Calculations in Maryland 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% slope

General trends for results of K Calculations in Maryland Western Coastal Plain and Upper Eastern Shore Soils • K for ~ 20% components will increase by 1 or more classes Ø ~ 39% are C and D slope map units • K for ~ 48% components will decrease by 1 or classes Ø ~ 37% are C and D slope map units

General trends for results of K Calculations in Maryland Piedmont Soils • K for ~ 35% components will increase by 1 or more classes Ø ~ 46% are in C and D slope map units • K for ~ 22% components will decrease by 1 or more classes Ø ~ 37% are in C and D slope map units

General trends for results of K Calculations in Maryland Mountain Soils • K for ~ 28% components will increase by 1 or more classes Ø ~ 46% are in C and D slope map units • K for ~ 45% components will decrease by 1 or more classes Ø ~ 25% are in C and D slope map units

Half Way Through Questions so far?

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

HEL DETERMINATIONS Three Areas of Importance • When to use Frozen 1990 HEL Map unit list • Field visit for PHEL areas or where SS updated since 1990 • CRP – Different HEL Determinations

HEL Frozen Map Unit List - 1990 • Used for HEL or NHEL • PHEL - onsite required for determination to verify HEL or NHEL

Field Visit Includes PHEL Map Units • Verify 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)

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

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

NRCS/FSA HEL DETERMINATIONS Highly Erodible Land v. HEL Frozen Map Unit List - 1990 Maryland COMAR HES Highly Erodible Soils v. Soils with a slope >15 % or v. Soils with a K value >0. 35 and with slopes >5 %

NOT TIME TO RELAX YET! Questions?

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 maintained • Classes - 1, 2, 3, 4, and 5 • T factors - represent the goal for maximum annual soil loss

T Factor - Soil Loss Tolerance 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 19 Soil Characteristic in Criteria: • Organic • Bedrock • Fragmental • Rock fragments • Fragipan • Sandy substratum • High aluminum

T Factor Calculations Maryland Soil Property Changes Piedmont/Mountain Soils • Bedrock • Fragipan • Rock fragments Coastal Plain Soils • Sandy substratum • High aluminum (may over ride)

Where is T factor used? • NRCS RUSLE 2 • NRCS – Highly Erodible Land (HEL) • NRCS – Many Conservation Programs • State Land Planning Programs

General trends for results of T Calculations in Maryland 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 1 or more classes

General trends for results of T Calculations in Maryland Western Coastal Plain and Upper Eastern Shore Soils • T for ~17% map unit acreage will increase by 1 or more classes • T for ~35% map unit acreage will decrease by 1 or more classes

General trends for results of T Calculations in Maryland Piedmont Soils • T for ~8% map unit acreage will increase by 1 or more classes • T for ~10% map unit acreage will decrease by 1 or more classes

General trends for results of T Calculations in Maryland Mountain Soils • T for ~5% map unit acreage will increase by 1 or more classes • T for ~12% map unit acreage will decrease by 1 or more classes

Questions?

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

Hydrology Soil Groups Criteria - uses soil properties that influence runoff potential Soil Properties: • Depth to a seasonal high water table • Saturated 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.

General HSG Descriptions Based on all when thoroughly wet • Group A Soils - low runoff potential • Group B Soils - moderately low runoff potential • Group C – Soils moderately high runoff potential • Group D – Soils high runoff potential or high water table

General HSG Descriptions Based on all when thoroughly wet • Duel 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.

HSG’s Calculations Maryland Soil Property Changes Pre Calculations: • Assignment to group by general criteria guidelines • Example A group: high infiltration rate; deep; well drained to excessively drained sands or gravels • Example C group: slow infiltration rate; moderately fine to fine texture

HSG’s Calculations Maryland Soil Property Changes Present Calculations: • Assignment to group by detailed calculation of very specific criteria • Example A group:

HSG’s Calculations Maryland Soil Property Changes Present Calculations: • Example A group:

HSG’s Calculations Maryland Soil Property Changes Present Calculations for Duel Classes: • Example A/D group: WT break is on 24” • Our Drainage class breaks at 20” • Now SWPD have duel classes

Hydrology Soil Groups Where used? • HSG’s used in equations that estimate runoff from rainfall. • Solving hydrologic problems in planning watershed protection • Flood prevention projects • Planning & designing structures for the use, control, and disposal of water.

Hydrology Soil Groups Where used? • Many Federal, State, and Local Engineering Land Use Management programs and practices and BMP’s • RUSLE 2 for use in Subsurface Drainage Systems • NRCS Waste Management Soil Interpretations • MDE - SWM and SEC Practices

General trends for results of HSG Calculations in Maryland Coastal Plain Soils • B to other class – 38% of components Piedmont and Mountain Soils • D to Duel – 11% of components • C to D – 10% of components • C to B – 9% of components • B to A - 8% of components

Questions? james. brewer@md. usda. gov 410 822 1577 x 121