1 / 143

WIND EROSION EQUATION

Training Objectives. We will discuss the Critical Period Method and the Management Period Method. Training Objectives. The WEQ factorsAdjustments to I" that mayincrease I" factor valuesdecrease I" factor valuesEffect of I" on soil erosion rates. Training Objectives. Understand the WEQ K" f

fred
Download Presentation

WIND EROSION EQUATION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. WIND EROSION EQUATION Predicting Soil Erosion by Wind A Guide to Conservation Planning

    2. Training Objectives We will discuss the Critical Period Method and the Management Period Method

    3. Training Objectives The WEQ factors Adjustments to “I” that may increase “I” factor values decrease “I” factor values Effect of “I” on soil erosion rates

    4. Training Objectives Understand the WEQ “K” factor Be able to plan the contribution of “Ridge Roughness” in controlling erosion from wind Be able to plan the contribution of “Random Roughness” in controlling wind erosion

    5. Training Objectives “K” is a measure of the effect on wind erosion of ridges made by tillage and planting implements. Ridges absorb and deflect wind energy, and trap moving soil particles.

    6. E = Estimated Average Annual Soil Loss in Tons per Acre per Year I=Potential soil loss (tons/ac) K=Roughness (ridge and random) C=Climatic (wind energy and direction) L=Unshelter distance (ft) V=Residue and growing crop (SGe) WIND EROSION EQUATION

    7. WIND EROSION CONTROL

    8. WIND EROSION PROCESSES

    9. WIND EROSION EQUATION “I” - Soil Erodibility Index K C L V

    10. “I” SOIL ERODIBILITY INDEX “I” expresses the potential annual wind erosion in tons/acre/year, from a site that is wide, level, unsheltered, and isolated; has a bare, smooth, loose, and non-crusted surface; and has climate conditions like those in the vicinity of Garden City, Kansas.

    11. “I” SOIL ERODIBILITY INDEX Wide - the distance at which the flow of eroding particles reach their maximum and does not increase with field size Level - there are no knolls present Unsheltered - there are no barriers Isolated - there is no incoming saltation

    12. Bare - no vegetation is present Smooth - there are no effects from ridge roughness Loose - soil aggregates are not bound together Non-crusted - the surface is not crusted

    13. “I” SOIL ERODIBILITY INDEX

    14. WEG AND I FOR SOIL TEXTURE CLASSES

    15. ADJUSTMENTS TO “I” Knolls - increase I Surface crusting - decreases I Clod-forming tillage - decreases I Irrigation adjustment - decreases I

    16. KNOLL ERODIBILITY

    17. ADJUSTMENTS TO “I” Surface crusting crusts form when soils are wetted and dried a fully crusted soil may erode only 1/6 as much as a non-crusted soil make adjustments only when using the Management Period Method

    18. ADJUSTMENTS TO “I” Clod-forming tillage: used in emergency situations to increase non-erodible clods on the soil surface tilled to create clods and crevices deep-plowing to bring up finer-textured soil that will form more persistent clods develop ridge-furrow configuration

    19. ROUGHNESS TYPES

    20. Summary slide for I and K. These surfaces illustrate those that reflect the adjustments to I and K in WEQ.Summary slide for I and K. These surfaces illustrate those that reflect the adjustments to I and K in WEQ.

    21. ADJUSTMENTS TO “I” Irrigation adjustment supporting data is limited reduction observed in the field adjustment would apply to all soils except fine and very fine sands

    22. ADJUSTMENTS TO “I” - IRRIGATION

    23. EFFECT OF I FACTOR VALUE ON EROSION RATE

    24. EFFECT OF I FACTOR VALUE ON EROSION RATE

    25. “I” FACTOR SUMMARY “I” represents soil loss in tons/acre/year, and is modified by the other erosion factors (K, C, L &V) “I” is determined by sieving to establish the percent of non-erodible aggregates greater than 0.84 mm in diameter

    26. “I” FACTOR SUMMARY Adjustments to “I” Knolls (increases “I”) Surface crusts (decreases “I”) Clod-forming tillage (decreases “I”) Irrigation (decreases “I”)

    27. WIND EROSION EQUATION I “K” - Ridge Roughness C L V

    28. “K”- RIDGE ROUGHNESS FACTOR

    29. ROUGHNESS TYPES

    30. EROSION AND DEPOSITION PROCESSES ON RIDGES

    31. RELATIONSHIP OF RIDGE ROUGHNESS TO A SOIL RIDGE ROUGHNESS FACTOR

    32. INFORMATION NEEDED TO DETERMINE THE “K” FACTOR Ridge height Ridge spacing Angle of deviation prevailing wind erosion direction (PWED) row direction

    33. “K” FACTOR TABLE

    34. ANGLE OF DEVIATION The angle of deviation is the angle between the prevailing wind erosion direction (PWED) and a line perpendicular to the row direction

    35. WIND EROSION DIRECTION The direction the wind is coming from

    37. WIND DIRECTIONS

    38. EFFECT OF PWED ON “K” FACTOR

    39. ANGLE OF DEVIATION TABLE

    41. “K” RIDGE ROUGHNESS FACTOR

    42. “K” RIDGE ROUGHNESS FACTOR

    43. “K” RIDGE ROUGHNESS FACTOR

    44. “K” RIDGE ROUGHNESS FACTOR

    45. “K” RIDGE ROUGHNESS FACTOR Angle of Deviation = 90o Soil ridge roughness, K factor, is always 1.0 when the prevailing wind erosion direction is parallel to the ridge pattern (angle of deviation = 90o).

    46. “K” RANDOM ROUGHNESS FACTOR Non-oriented surface roughness Cloddiness Usually created by tillage implements Values represented as standard deviation of roughness heights

    47. “K” RANDOM ROUGHNESS FACTOR Raises threshold wind speed at which erosion begins Provides some sheltered area among clods where moving soil can be trapped Degrades much faster than oriented roughness

    48. “K” RANDOM ROUGHNESS FACTOR Random roughness and ridge roughness are complementary Factor values multiplied together to get total roughness “K” factor value.

    49. “K” RANDOM ROUGHNESS VALUES

    50. EFFECT OF K FACTOR VALUE ON EROSION RATE

    51. EFFECT OF K FACTOR VALUE ON EROSION RATE

    52. ANGLE OF DEVIATION TABLE

    53. COMPUTING ANGLE OF DEVIATION WHEN ROWS ARE NOT EAST/WEST OR NORTH/SOUTH

    54. RULES OF THUMB The angle of deviation is always from 0 to 90 degrees. Ridges in a field actually have two directions. The second direction of a ridge can be computed by adding 180 degrees to the first ridge direction.

    55. RULES OF THUMB This applies to the line perpendicular to the ridge direction as well as the ridge direction. The opposite cardinal point of 45 degrees is 225 degrees.

    56. RULES OF THUMB The angle of deviation is computed by relating the prevailing wind erosion direction to the direction of the perpendicular line. Angle of deviation charts are available for 0, 22.5, 45, 67.5, and 90 degrees.

    57. EXAMPLE When the ridge direction is not within 90 degrees of the prevailing wind direction: Move to the second direction of the perpendicular line which is 180 degrees different from the given ridge direction.

    58. EXAMPLE The angle of deviation is the difference, in degrees, between the prevailing wind direction and the direction of the line perpendicular to the ridge direction.

    59. “K” FACTOR SUMMARY Ridges and furrows affect the detachment, transport, and deposition of soil particles Ridges are most effective when they are perpendicular to the prevailing wind erosion direction The “K” factor accounts for oriented roughness and random roughness

    60. WIND EROSION EQUATION I K “C” - Climatic Factor L V

    61. “C” FACTOR OBJECTIVES Participants will understand: The WEQ “C” factor Climatic effects to determine “C” Erosive wind energy distribution

    62. “C” CLIMATIC FACTOR The “C” factor is an index of the relative influence of climate on soil erodibility by wind at a given site; specifically, the effects of average windspeed and effective soil surface moisture.

    63. “C” - CLIMATIC FACTOR Based on long-term climatic data Expressed as a percentage value Example: C = 40, 40%, or .40

    64. “C” CLIMATIC FACTOR Required information Average annual windspeed Average monthly precipitation Average monthly temperature

    65. THORNTHWAITE’S PE INDEX PE - precipitation-effectiveness index P - average monthly precipitation T - average monthly temperature

    66. “C” - CLIMATIC FACTOR C - annual climatic factor 34.38 - constant V - average annual wind velocity PE - annual precipitation effectiveness index

    67. “C” - CLIMATIC FACTOR General concepts As the average annual wind speed increases, “C” factor values increase As the average monthly precipitation increases, “C” factor values decrease As the average monthly temperature increases, “C” factor values increase

    68. “C” FACTOR CALCULATION

    69. C FACTOR ISOLINE MAP - U.S.

    70. C FACTOR ISOLINE MAP - LOCAL AREA

    71. EROSIVE WIND ENERGY DISTRIBUTION Expected distribution of erosive wind energy By month For specific geographic location

    72. EWE DISTRIBUTION TABLES

    73. EROSIVE WIND ENERGY DISTRIBUTION FOR SELECTED LOCATIONS

    74. EWE IRRIGATION ADJUSTMENT Effects of wetting and drying can be accounted for by adjusting the EWE Bare wet soil remains non-erodible: 1 day for coarse textured soils 2 days for medium textured soils 3 days for fine textured soils Applies only to period when irrigation occurs

    76. E TABLE FOR C = 100, I = 86, K=1.0

    77. E TABLE FOR C = 50, I = 86, K = 1.0

    78. “C” FACTOR SUMMARY “C” is an index of relative influence of climate on erosion at a given location “C” considers average annual wind speed average monthly precipitation average monthly temperature

    79. “C” FACTOR SUMMARY “C” is expressed as a percentage value of conditions at Garden City, Kansas Erosive wind energy distribution is used in the Management Period Method On irrigated fields, EWE is adjusted during time period when irrigation occurs

    80. Summary slide for I and K. These surfaces illustrate those that reflect the adjustments to I and K in WEQ.Summary slide for I and K. These surfaces illustrate those that reflect the adjustments to I and K in WEQ.

    81. WIND EROSION EQUATION I K C “L” - Unsheltered distance V

    82. “L” FACTOR OBJECTIVES Participants will understand: The WEQ “L” factor. Prevailing Wind Erosion Direction (PWED). Preponderance. The effect of barriers on “L”. How to determine “L”.

    83. “L” - UNSHELTERED DISTANCE The unsheltered distance along the prevailing wind erosion direction for the field or area to be evaluated

    84. “L” REPRESENTS The distance from a point upwind where no saltation or surface creep occurs and to the downwind edge of the field or area being evaluated.

    85. “L” - UNSHELTERED DISTANCE

    86. “L” - UNSHELTERED DISTANCE

    87. “L” - UNSHELTERED DISTANCE

    88. FIELD WITH INTERNAL STABLE CONDITION

    89. STABLE CONDITION An area with sufficient vegetative cover to trap and hold expected saltation and surface creep from upwind.

    90. STABLE CONDITION

    91. BARRIER A continuous strip or row of trees, shrubs, or tall grass having sufficient height and density to create a sheltered zone downwind.

    92. GRASS BARRIERS

    93. TREE BARRIER

    94. “L” - UNSHELTERED DISTANCE

    95. “L” - UNSHELTERED DISTANCE

    96. INFORMATION TO DETERMINE “L” Prevailing wind erosion direction at various times of the year. Preponderance values. Field length to width ratio. Field orientation. Angle of deviation. Wind erosion direction factor.

    97. PREVAILING WIND EROSION DIRECTION (PWED) Direction from which the greatest amount of erosive wind occurs for the period being evaluated

    98. WIND DIRECTION AND ANGLE OF DEVIATION

    99. PREPONDERANCE Ratio between wind forces parallel and wind forces perpendicular to the PWED. Includes winds blowing both directions along identified direction. A low preponderance indicates wind forces are complex. A high preponderance indicates wind forces tend to parallel PWED.

    100. EWE DISTRIBUTION TABLES

    101. FIELD LENGTH:WIDTH RATIO & ORIENTATION

    102. ANGLE OF DEVIATION FOR “L” Angle between the PWED and a line perpendicular to the long side of the field or area being evaluated.

    104. WIND DIRECTION AND PREPONDERANCE

    105. ANGLE OF DEVIATION TABLE*

    106. STEPS IN DETERMINING “L” 1. Obtain values for PWED and preponderance. 2. Measure actual length and width of field, and determine length:width ratio. 3. Determine angle of deviation between PWED and a line perpendicular to the long side of the field.

    107. STEPS IN DETERMINING “L”

    108. WIND EROSION DIRECTION FACTOR TABLE

    109. WIND EROSION DIRECTION FACTOR TABLE

    110. E TABLE FOR C = 100, I = 86, K=1.0

    111. E TABLE - C=90, I=134, K=1.0*

    112. EXAMPLE FIELD

    113. “L” FACTOR SUMMARY “L” represents the unsheltered distance. “L” always begins at a stable boundary. Prevailing wind direction, angle of deviation, and preponderance must be accounted for when determining “L”. Barriers reduce the unsheltered distance.

    114. WIND EROSION EQUATION I K C L “V” - Vegetative cover

    115. “V” FACTOR OBJECTIVES Participants will: Understand the WEQ “V” factor Understand the term “flat small grain equivalent” Be familiar with the factors affecting vegetative cover

    116. “V” FACTOR OBJECTIVES Participants will: Be familiar with methods used to predict quantities of residue Be able to use the SGe tables to convert amounts of vegetative cover to flat small grain equivalents

    117. “V” - VEGETATIVE COVER This factor considers the kind, amount, and orientation of vegetation on the surface Vegetative cover is expressed in pounds per acre of flat small grain equivalent

    118. SGe REFERENCE CONDITION 10 inch stalks of small grain lying parallel to the wind direction Rows spaced 10 inches apart perpendicular to the wind

    119. SGe GRAPH FOR SMALL GRAIN

    120. EXAMPLES OF MASS VS. COVER

    121. FACTORS AFFECTING RESIDUE EFFECTIVENESS Residue kind Residue amount Residue orientation

    122. EFFECT OF RESIDUE KIND & AMOUNT

    123. ORIENTATION OF RESIDUE Standing vs. Flat Perpendicular vs. Parallel to wind

    124. Corn Residue STANDING vs FLAT

    125. FLAT vs RIDGED

    126. PERPENDICULAR vs PARALLEL TO WIND

    127. PRINCIPLES OF RESIDUE EFFECTIVENESS Standing residue is more effective than equal weights of flat residue Pound for pound, finer residues (smaller diameter) are more effective than coarse residues Plants and residue in rows perpendicular to the wind are more effective than rows parallel to the wind

    128. METHODS FOR ESTIMATING RESIDUE AMOUNT Clip and weigh Picture comparison Line transect Estimation through use of residue yield ratios & tillage reduction values

    129. LINE TRANSECT METHOD Need 50’ rope with 100 marks on it Lay at 45 degree angle Count number of residue hits Take minimum of 3 samples Convert to percent cover Convert percent cover to lbs/ac

    130. RESIDUE PERCENT COVER TO WEIGHT CONVERSION TABLES

    131. YIELD/RESIDUE RATIOS

    132. RESIDUE REDUCTION BY TILLAGE

    133. FRAGILE AND NON-FRAGILE CROP RESIDUES NON-FRAGILE Alfalfa or legume hay Corn/Popcorn/Sorghum Flaxseed Forage seed/silage Grass hay/Pasture Millet Rice Small grains* Speltz* Sugarcane FRAGILE Canola/Rapeseed/Mustard Dry Beans/Dry Peas/Lentils Fall-seeded cover crops Flower seed Grapes Green peas Potatoes (white, red and sweet) Safflower/Sunflower Sugar Beets Vegetables

    134. DETERMINING WEIGHTED SGe FOR MIXED COVER/COMPONENTS MIXED ORIENTATION TYPES - FLAT AND STANDING RESIDUES 2500 lb total winter wheat residue 1500 lb/acre (60%) standing 1000 lb/acre (40%) flat Using SGe curves based on total residue: SGe contribution from standing component 2500 lb/acre standing = 8500 lb/acre SGe X 60% = 5100 lb/acre SGe SGe contribution from flat component: 2500 lb/acre flat = 3300 lb/acre SGe X 40% = 1320 lb/acre SGe Weighted average = 5100+1320 =6420 lb/acre SGe

    135. DETERMINING WEIGHTED SGe FOR MIXED COVER/COMPONENTS MIXED ORIENTATION TYPES - GROWING CROP AND FLAT RESIDUES 1300 lb/acre winter wheat residue and growing grain sorghum 300 lb/acre (23%) growing grain sorghum 1000 lb/acre (77%) flat winter wheat residue Using SGe curves based on total residue SGe contribution from growing crop component 1300 lb/acre growing grain sorghum crop = 7000 lb/acre SGe X 23% = 1610 lb/acre SGe SGe contribution from flat residue component 1300 lb/acre flat wheat residue = 2000 lb/acre SGe X 77% = 1540 lb/acre SGe Weighted average = 1610 + 1540 = 3150 lb/acre SGe

    136. “V” FACTOR SUMMARY Considers the kind, amount and orientation of vegetation Is expressed in pounds per acre of flat small grain equivalent (SGe) Methods available to determine the amount of residue present include clip & weigh, picture comparison, line transect, and yield/tillage reduction

    138. SOIL AND CROP TOLERANCE Participants will understand soil and crop tolerances to blowing soil, and their consideration in planning conservations systems

    139. SOIL LOSS TOLERANCE Average annual soil erosion rateAverage annual soil erosion rate

    140. CROP TOLERANCE extremely variable with crops and value of product.extremely variable with crops and value of product.

    141. ADVERSE IMPACTS ON CROPS Blow outs Exposed root systems Moisture loss in leaves & stems Sand blasting or plant abrasion

    142. TOLERANCE OF CROPS TO WIND AND/OR BLOWING SOIL

    143. ESTIMATED CROP TOLERANCE TO BLOWING SOIL T = 5 T/AcT = 5 T/Ac

    144. SOIL AND CROP TOLERANCE Summary: Soil loss tolerance defined Crop tolerance defined Impacts on growing crops Categories of growing crops

More Related