REVISED UNIVERSAL SOIL
LOSS EQUATION-Version 2
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Predicting Soil Erosion By Water: A Guide to Conservation Planning |
UNIT 1
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Course Objectives and Topics |
OBJECTIVES
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Understand erosion processes |
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Learn RUSLE2 and its software |
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Learn field office applications of
RUSLE2 |
UNIT 2
OVERVIEW OF EROSION
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Definition of erosion |
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Erosion processes |
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Types of erosion |
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Why erosion is a concern |
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Uses of erosion prediction tools |
EROSION
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“Erosion is a process of detachment and
transport of soil particles by erosive agents.” |
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Ellison, 1944 |
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Erosive Agents |
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Raindrop impact |
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Overland flow surface runoff from
rainfall |
DETACHMENT
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Removal of soil particles from soil
surface |
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Adds to the sediment load |
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Sediment load: Rate sediment is
transported downslope by runoff |
DETACHMENT
DEPOSITION
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Reduces the sediment load |
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Adds to the soil mass |
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Local deposition |
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Surface roughness depressions |
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Row middles |
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Remote deposition |
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Concave slope |
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Strips |
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Terraces |
DEPOSITION
TYPES OF EROSION
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Interrill and rill (sheet-rill) |
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Ephemeral gully |
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Permanent, incised (classical) gully |
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Stream channel |
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Mass movement |
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Geologic |
DEFINITIONS
DEFINITIONS
DEFINITIONS
DEFINITIONS
DEFINITIONS
LOCAL DEPOSITION
Credit for Deposition
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Local Deposition |
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Full credit |
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Remote Deposition |
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Partial credit |
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Amount |
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Location |
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Spacing of terraces |
SEDIMENT CHARACTERISTICS
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Particle Classes |
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Primary clay, primary silt, small
aggregate, large aggregate, primary sand |
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At Detachment |
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Distribution of classes function of
texture |
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Diameter of small and large aggregates
function of texture |
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After Deposition |
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Sediment enriched in fines |
EROSION IS A CONCERN
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Degrades soil resource |
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Reduces soil productivity |
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Reduces soil organic matter |
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Removes plant nutrients |
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Causes downstream sedimentation |
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Produces sediment which is a pollutant |
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Produces sediment that carries
pollutants |
WHERE EROSION CAN BE A
PROBLEM
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Low residue crops |
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Conventional tillage |
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Rows up/down steep slopes |
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Low maintenance pasture |
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Disturbed land with little cover |
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EROSION PREDICTION AS A
TOOL
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Guide management decisions |
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Evaluate impact of erosion |
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Inventory soil erosion |
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Conservation planning |
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EROSION PREDICTION AS A
TOOL
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Concept: |
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Estimate erosion rate |
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Evaluate by ranking |
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Evaluate against quality criteria |
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Tool: RUSLE2 |
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Quality Criteria: Soil loss tolerance |
PLANNING VARIABLES
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Soil loss on eroding portions of
hillslope |
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Detachment (sediment production) on
hillslope |
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Conservation planning soil loss for
hillslope |
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Ratio of segment soil loss to soil
tolerance adjusted for segment position |
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Sediment yield from hillslope/terraces |
UNIT 3
OVERVIEW OF RUSLE2
(Revised Universal Soil Loss Equation-Version 2)
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Where RUSLE2 applies |
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Major factors affecting erosion |
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RUSLE2 factors |
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RUSLE2 background |
Landscape
FACTORS AFFECTING
INTERILL-RILL EROSION
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Climate |
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Soil |
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Topography |
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Land use |
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Cultural practices |
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Supporting practices |
RUSLE2 FACTORS
Daily Soil Loss
a = r k l s c p
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r - Rainfall/Runoff |
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k - Soil erodibility |
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l - Slope length |
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s - Slope steepness |
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c - Cover-management |
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p - Supporting practices |
RUSLE FACTORS
(Sediment Production)
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Climate r |
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Soil k |
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Topography ls |
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Land Use and lscp |
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Management |
RUSLE FACTORS
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A = f (erodibility, erosivity) |
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Erosivity – rklscp |
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Erodibility - klc |
RUSLE FACTORS
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Unit Plot Concept |
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a = rk
lscp |
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rk - Unit plot soil loss |
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(dimensions) |
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lscp - Adjusts unit plot soil loss |
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(dimensionless) |
Slide 33
Slide 34
How Deposition at a Grass
Strip Affects Sediment Characteristics
RUSLE2 BACKGROUND
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Combines empirical field data-process
based equations |
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(natural runoff and rainfall simulator
plots) |
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Zingg’s equation (1940) |
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Smith and Whit’s equation (1947) |
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AH-282 (1965) |
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“Undisturbed land” (1975) |
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AH-537 (1978) |
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Disturbed forestland (1980) |
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RUSLE1 (1992) |
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AH703 (1997) |
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OSM Manual (mined, reclaimed land,
construction sites) (1998) |
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RUSLE2 (2001) |
RUSLE2 APPLICATIONS
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Cropland |
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Pastureland |
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Rangeland |
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Disturbed forest land |
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Construction sites |
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Surface mine reclamation |
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Military training lands |
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Parks |
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Waste disposal/landfills |
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SUMMARY
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Factors affecting erosion |
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RUSLE2 factors |
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RUSLE2 background |
Unit 4
RUSLE2 Factors
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r- erosivity factor |
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k- erodibility factor |
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l- slope length factor |
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s- slope steepness factor |
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c- cover-management factor |
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p- supporting practices factor |
EROSIVITY
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Single storm |
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Energy x 30 minute intensity |
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Fundamentally product of rainfall
amount x intensity |
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Annual-sum of daily values |
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Average annual-average of annual values |
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Daily value=average annual x fraction
that occurs on a given day |
EROSIVITY - R
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Las Vegas, NV 8 |
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Phoenix, AZ 22 |
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Denver, CO 40 |
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Syracuse, NY 80 |
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Minneapolis, MN 110 |
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Chicago, IL 140 |
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Richmond, VA 200 |
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St. Louis, MO 210 |
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Dallas, TX 275 |
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Birmingham, AL 350 |
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Charleston, SC 400 |
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New Orleans, LA 700 |
Erosivity Varies During
Year
10 yr EI
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Reflects locations where intense,
erosive storms occur that have a greater than proportional share of their
effect on erosion |
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Effectiveness and failure of contouring |
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Effect of ponding on erosivity |
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Sediment transport capacity |
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Reduction by Ponding
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Significant water depth reduces
erosivity of raindrop impact |
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Function of: |
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10 yr EI |
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Landslope |
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SOIL ERODIBILITY - K
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Measure of soil erodibility under
standard unit plot condition |
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72.6 ft long, 9% steep, tilled
continuous fallow, up and down hill tillage |
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Independent of management |
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Major factors |
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Texture, organic matter, structure,
permeability |
SOIL ERODIBILITY - K
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Effect of texture |
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clay (0.1 - 0.2) resistant to
detachment |
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sand (0.05 - 0.15) easily detached, low
runoff, large, dense particles not easily transported |
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silt loam (0.25 - 0.35) moderately
detachable, moderate to high runoff |
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silt (0.4 -0.6) easily detached, high
runoff, small, easily transported sediment |
Time Variable K
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Varies during year |
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High when rainfall is high |
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Low when temperature is high |
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Very low below about 25 °F |
Time Variable K
TOPOGRAPHY
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Overland flow slope length |
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Slope lengths for eroding portions of
hillslopes |
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Steepness |
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Hillslope shape |
Hillslope Shape
Overland Flow Slope
Length
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Distance from the origin of overland
flow to a concentrated flow area |
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This slope length used when the
analysis requires that the entire slope length be considered. |
Slope Length for Eroding
Portion of Slope
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Only works for simple slopes |
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Traditional definition |
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Distance from origin of overland flow
to concentrated flow or to where deposition begins |
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Definition is flawed for strips and
concave:convex slopes |
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Best approach: Use overland flow slope
length and examine RUSLE2 slope segment soil loss values |
Slide 54
Slope Length for Concave
Slope
Rule of Thumb for
Deposition Beginning on Concave Slopes
Slope Length for
Concave:Convex Slope
Slide 58
Basic Principles
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Sediment load accumulates along the
slope because of detachment |
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Transport capacity function of distance
along slope (runoff), steepness at slope location, cover-management, storm
severity (10 yr EI) |
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Deposition occurs where sediment load
becomes greater than transport capacity |
Detachment Proportional
to Slope Length Factor
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Slope length effect |
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l= (x/72.6)n |
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x = location on slope |
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n = slope length exponent |
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Slope length exponent |
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Related to rill:interrill ratio |
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Slope steepness, rill:interrill
erodibility, ground cover, soil biomass, soil consolidation |
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Slope length factor varies on a daily
basis |
Slope Length Effects
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Slope length effect is greater on
slopes where rill erosion is greater relative to interrill erosion |
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Examples: |
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Steep slopes |
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Soils susceptible to rill erosion |
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Soils recently tilled |
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Low soil biomass |
Detachment Proportional
to Slope Steepness Factor
Effect of Slope Shape on
Erosion
Land Use
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Cover-management |
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Supporting practices |
Cover-Management
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Vegetative community |
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Crop |
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Crop rotation |
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Conservation tillage |
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Application of surface and buried
materials (mulch, manure) |
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Increasing random roughness |
Supporting Practices
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Contouring |
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Strip systems |
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Buffer, filter, strip cropping,
barriers |
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Terrace/Diversion |
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Impoundments |
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Tile drainage |
Cover-Management
Subfactors
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Canopy |
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Ground cover |
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Surface Roughness |
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Ridges |
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Below ground biomass |
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Live roots, dead roots, buried residue |
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Soil consolidation |
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Antecedent soil moisture (NWRR only) |
Cover-Management Effects
Canopy
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Cover above soil surface that
intercepts rainfall but does not touch soil surface to affect surface flow |
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Main variables |
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Percent of surface covered by canopy |
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Effective fall height |
Effective Fall Height
Ground Cover
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Cover directly in contact with soil
surface that intercepts raindrops, slows runoff, increases infiltration |
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Examples |
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Live plant material |
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Plant residue and litter |
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Applied mulch |
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Stones |
Ground Cover Effect
Ground Cover
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Live cover depends on type of
vegetation, production level, and
stage |
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Residue |
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Amount added by senescence, flattening,
and falling by decomposition at base |
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Decomposition |
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Rainfall amount |
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Temperature |
Interaction of Ground
Cover and Canopy
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Canopy over ground cover is considered
to be non-effective |
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As fall height approaches zero, canopy
behaves like ground cover |
Random Roughness
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Creates depressions |
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Usually creates erosion resistant clods |
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Increases infiltration |
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Increases hydraulic roughness that
slows runoff, reducing detachment and transport capacity |
Random Roughness
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Standard deviation of micro-elevations |
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Roughness at tillage function of: |
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Implement |
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Roughness at time of disturbance and
tillage intensity |
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Soil texture |
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Soil biomass |
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Decays with: |
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Rainfall amount |
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Interrill erosion |
Ridges
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Ridges up and downhill increase soil
loss by increasing interrill erosion |
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Function of: |
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Effect increases with ridge height |
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Effect decreases with slope steepness
above 6% |
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Ridge height decays with rainfall
amount and interrill erosion |
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Effect shifts from increasing soil loss
when up and downhill to decreasing soil loss when on the contour |
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Dead Biomass Pools
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Killing vegetation converts live
standing to dead standing and live roots to dead roots |
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Operations |
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Flatten standing residue to flat
residue (ground cover) |
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Bury flat residue |
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Resurface buried residue |
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Redistribute dead roots in soil |
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Material spread on surface |
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Material incorporated (lower one half
of depth of disturbance) |
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Decomposition at base causes standing
residue to fall |
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Decomposition of Dead
Biomass
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Function of: |
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Rainfall |
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Temperature |
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Type of material |
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Standing residue decays much more
slowly |
Below ground biomass
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Live roots |
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Distributed non-uniformly within soil |
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Dead roots |
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Buried residue |
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Half of material decomposed on surface
is added to upper 2 inches |
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Incorporated biomass |
Effect of Below Ground
Biomass
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Roots mechanically hold the soil |
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Add organic matter that improves soil
quality, reduces erodibility, increases infiltration |
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Affect rill erosion more than interrill
erosion |
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Effect of roots considered over upper
10 inches |
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Effect of buried residue over upper 3
inches, but depth decreases to 1 inch as soil consolidates (e.g. no-till) |
Soil Consolidation
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Overall, freshly tilled soil is about
twice as erodible as a fully consolidated soil |
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Erodibility decreases with time |
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Seven years in the Eastern US |
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Depends on rainfall in Western US, up
to 25 years |
Width of Disturbance
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Width of disturbance taken into account
in surface cover, random roughness, and soil consolidation |
Antecedent Soil Moisture
(NWRR)
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Soil loss depends on how much moisture
previous cropping systems have removed from soil |
Supporting Practices
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Contouring/Cross-slope farming |
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Strips/barriers |
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Rotational strip cropping, buffer
strips, filter strips, grass hedges, filter fence, straw bales, gravel bags |
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Terraces/diversions |
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Impoundments |
Contouring/Cross Slope
Farming
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Redirects runoff |
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Fail at long slope lengths |
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Effectiveness depends on ridge height |
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(no ridge height—no contouring effect) |
Contouring/Cross Slope
Farming (continued)
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Function of: |
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Ridge height |
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Row grade |
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Cover-management |
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Hydrologic soil group |
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Storm severity (10 yr EI) |
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Varies with time |
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Tillage that form ridges |
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Decay of ridges |
Critical Slope Length
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If slope length longer than critical
slope length, contouring fails allowing excessive rill erosion |
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Function of: |
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Storm severity, slope steepness,
cover-management, EI distribution |
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Critical slope length extensions below
strips depend on degree that strip spreads runoff |
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Terraces are used if changing
cover-management or strips are not sufficient |
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Soil disturbance required to restore
failed contouring |
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Buffer/Filter Strips
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Narrow strips of dense vegetation
(usually permanent grass) on contour |
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Effective by inducing deposition
(partial credit) and spreading runoff |
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Most of deposition is in backwater
above strip |
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Buffer strips |
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Multiple strips |
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Either at bottom or not a strip at
bottom |
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Water quality-must have strip at bottom
and this strip twice as wide as others |
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Filter strip-single strip at bottom |
Rotational Strip Cropping
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Equal width strips on contour |
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Strips are rotated through a crop
rotation cycle |
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Offset starting dates among strips so
that strips of close growing vegetation separate erodible strips |
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Benefit: |
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Deposition (full credit) |
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Spreading runoff |
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Reduced ephemeral gully erosion not
credited in RUSLE2 |
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Terraces
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Ridges and channels periodically placed
along hillslope that divides hillslope into shorter slope lengths except for
widely spaced parallel terraces that may have not effect on slope length |
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Benefit: |
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Shorten slope length and trap sediment |
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Runoff management system |
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Evenly spaced |
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May or may have a terrace at bottom |
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Maintenance required to deal with
deposition |
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Slide 92
Deposition in Terraces
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Deposition occurs when sediment load is
greater than transport capacity |
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Sediment load from sediment entering
from overland area |
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Transport capacity function of grade
and storm erosivity |
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Deposition depends on sediment
characteristics |
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Deposition enriches sediment in fines |
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Diversions
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Ridges and channels placed at strategic
locations on hillslope to shorten slope length |
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Reduce runoff rate and rill erosion |
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Generally designed with a steepness
sufficiently steep that no deposition occurs but not so steep that erosion
occurs |
Impoundments (Small
sediment control basins)
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Deposition by settling process |
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Function of: |
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Sediment characteristic of sediment
load reaching impoundment |
Sequencing of Hydraulic
Elements
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Hydraulic elements-channels and
impoundments |
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Can create a system |
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Can put channels-impoundments in
sequence |
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Examples: |
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Tile outlet terrace—channel:impoundment |
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Impoundments in
series—impoundment:impoundment |
Benefit of Deposition
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Depends on type of deposition |
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Local deposition gets full credit |
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Remote deposition gets partial credit |
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Credit for remote deposition |
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Depends on location on hillslope |
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Deposition at end gets almost no credit |
Subsurface Drainage
Systems
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Reflects effects of deep drainage
systems |
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Tile drainage systems |
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Lateral, deep drainage ditches |
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Describe by: |
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Assigning hydrologic soil group for
undrained and drained soil |
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Fraction of area drained |
Unit 5
Databases
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Worksheets |
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Profiles |
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Climate |
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EI distribution |
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Soil |
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Management |
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Operations |
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Vegetation |
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Residue |
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Contouring |
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Strips |
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Diversion/terrace, sediment basin
systems |
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Sequence of hydraulic elements |
Profiles
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Central part of a RUSLE2 soil loss
estimate |
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Profile is reference to a hillslope
profile |
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Six things describe a profile |
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Location, soil, topography, management,
supporting practice, hydraulic element system |
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Topography described with profile |
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Can specify segments by length and
steepness for topography, segments by length for soil, segments by length for
management |
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Name and save with a name |
Worksheets
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Three parts: Alternative managements,
practices; Alternative profiles; Profiles for a field or watershed |
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Alternative management, practices |
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Compare alternatives for a single
hillslope profile |
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Alternative profiles |
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Compare specific hillslope profiles |
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Field/Watershed |
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Compute average soil loss/sediment
yield for a field or watershed |
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Name and save worksheets |
Concept of Core Database
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RUSLE2 has been calibrated to
experimental erosion data using assumed data values for such things as
cover-mass, residue at harvest, decomposition coefficient, root biomass,
burial ratios, etc. |
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The data used in this calibration are
core calibration values |
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Data used in RUSLE2 applications must
be consistent with these values |
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Core databases were set up for
vegetation, residue, and operations |
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NRCS data manager maintains these
databases |
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Working databases developed from the
core databases |
Critical RUSLE2 Rules
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RUSLE2 DEFINITIONS, RULES, PROCEDURES,
and CORE DATA MUST BE FOLLOWED FOR GOOD RESULTS. |
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Can’t independently change one set of
data without recalibrating. |
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Must let RUSLE2 factors and subfactors
represent what they were intended to represent. |
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For example, the K factor values are
not to be modified to represent the effect of organic farming. The cover-management subfactors represent
the effects of organic farming. |
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Don’t like these rules—then don’t use
RUSLE2 because results won’t be good. |
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Climate
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Input values for values used to
described weather at a location, county, management zone |
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Principal values |
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Erosivity value, 10 yr EI value, EI
distribution, monthly rainfall, monthly temperature |
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Designate as Req zone and corresponding
values |
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Data available from NRCS National
Weather and Climate Center |
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Name and save by location |
EI Distribution
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24 values that describe distribution of
erosivity R throughout year |
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For a location, county, management
zone, EI distribution zone |
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Data available from NRCS Weather and
Climate Center |
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Name and save |
Soil
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Data describes base soil conditions for
unit plot conditions |
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Data include erodibility value, soil
texture, hydrologic soil group of undrained soil, efficient subsurface
drainage, time to full soil consolidation, rock cover |
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Erodibility nomograph available to
estimate soil erodibility factor K |
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Data available from NRCS soil survey
database |
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Name and same |
Management
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Array of dates, operations, vegetations |
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Specify if list of operations is a
rotation |
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Rotation is a cycle when operations
begin to repeat |
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Rotations used in cropping |
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Rotations often not used immediately
after land disturbances like construction and logging during recovery period |
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Length of rotation |
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Yield, depth, speeds of operations |
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Added materials and amounts |
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NRCS databases, Extension Service |
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Name and save |
Operations
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Operations describe events that change
soil, vegetation, and residue conditions |
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Mechanical soil disturbance, tillage,
planting, seeding, frost, burning, harvest |
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Describe using effects and the sequence
of effects |
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Speed and depth |
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Source of data: Research core database,
NRCS core database, working databases |
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Name and save |
Operation Effects
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No effect |
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Begin growth |
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Kill vegetation |
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Flatten standing residue |
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Disturb surface |
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Live biomass removed |
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Remove residue/other cover |
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Add other cover |
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Operation Effects (cont)
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No effect |
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Primarily used to obtain output at
particular times or to add fallow years when not operation occurs in that
year |
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Begin growth |
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Tells RUSLE2 to begin using data for
particular vegetation starting at day zero |
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Typically associated with planting and
seeding operations |
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Kill vegetation |
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Transfers mass of above ground live
vegetation into standing residue pool |
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Transfers mass live roots into dead
root pool |
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Typically used in harvest and plant
killing operations |
Operation Effects (cont)
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Flatten standing residue |
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Transfer residue mass from standing
pool to flat, ground surface pool |
|
Based on a flattening ratio that is a
function of residue type |
|
Used in harvest operations to determine
fraction of residue left standing after harvest |
|
Used in tillage and other operations
involving traffic to determine fraction of residue left standing after
operation |
|
|
|
|
|
|
|
|
Operation Effects (cont)
|
|
|
|
Disturb surface |
|
For mechanical soil disturbance that
loosens soil |
|
Tillage type (inversion, mixing+some
inversion, mixing only, lifting fracturing, compression) determines where
residue is placed in soil and how residue and roots are redistributed within
soil |
|
Buries and resurfaces residue based on
ratios that depend on residue type |
|
Tillage intensity (degree that existing
roughness is obliterated) |
|
Recommended, minimum, maximum depths |
|
Initial ridge height |
|
Initial, final roughness (for the base
condition) |
|
Fraction surface area disturbed (tilled
strips) |
|
|
Operation Effects (cont)
|
|
|
|
Live biomass removed |
|
Fraction removed |
|
Fraction of that removed that is “lost”
and left as ground cover (flat residue) |
|
Used with hay and silage harvest
operations |
|
Remove residue/other cover |
|
All surface residues affected or only
most recent one? |
|
Fraction of standing cover removed |
|
Fraction of flat cover removed |
|
Used in baling straw, burning
operations |
|
|
Operation Effects (cont)
|
|
|
|
Add other cover |
|
Fraction added to surface versus
fraction placed in soil |
|
Unless all mass added to surface, must
be accompanied by disturbed soil effect (that is, mass can not be placed in
soil without disturbance) |
|
Mass placed in soil is placed between ½
and maximum depth |
|
Used to add mulch and manure to
surface, inject manure into soil |
|
|
Vegetation
|
|
|
|
Live plant material |
|
Static variables include: |
|
Residue name, yield, retardance,
senescence, moisture depletion for NWRR |
|
Time varying variables |
|
Root biomass in upper 4 inches |
|
Canopy cover percent |
|
Fall height |
|
Live ground (surface) cover cover
percent |
|
Source of data: Research core database,
NRCS core database, working databases |
|
Name and save |
|
|
|
|
Yield-Residue
Relationship
|
|
|
Residue at max canopy function of yield |
Yield-Retardance
Relationship
|
|
|
Residence function of yield, on
contour, and up and down hill |
Retardance for Up and
Downhill
|
|
|
|
RUSLE2 chooses retardance based on row
spacing and the retardance selected for a strip of the vegetation on the
contour |
|
How does vegetation slow the runoff? |
|
Row spacing |
|
Vegetation on ridge-no retardance
effect |
|
Wide row-no retardance effect (> 30
inches spacing) |
|
No rows, broadcast-same as strip on
contour |
|
Narrow row-small grain in about 7 inch
spacing |
|
Very narrow-same as narrow row except
leaves lay in row middle to slow runoff |
|
Moderate-about 15 to 20 inches spacing |
|
|
Residue
|
|
|
|
Size, toughness |
|
5 types: small, fragile (soybeans);
moderate size, moderately fragile (wheat); large size, nonfragile (corn);
large size, tough (woody debris); gravel, small stones |
|
Decomposition (coefficient, halflife) |
|
Mass-cover values |
|
Source: NRCS databases |
|
Name and save |
|
|
Senescence
|
|
|
Input the fraction of the biomass at
max canopy that falls to soil surface when canopy decreases from its max
value to its min value. |
|
Input the minimum canopy value that
corresponds to fraction that experiences senescence |
|
Mass that falls is computed from
difference in canopy percentages and nonlinear relationship between canopy
percent and canopy mass |
Contouring/Cross Slope
Farming
|
|
|
|
To have contouring, must have ridge
heights |
|
To have ridge height, must have
operation |
|
Ridge height assigned in operation |
|
Row grade |
|
Relative row grade (preferred) or
absolute |
|
Create contouring practices based on
relative row grade (row grade/land slope) |
|
Perfect (0%), exceeds NRCS specs (5%),
meets specs (10%), Cross slope (25%),
Cross slope (50%) |
|
Name and save contouring practice |
Strips/Barriers
|
|
|
|
Types |
|
Filter, buffer, rotational strip
cropping |
|
Filter |
|
Specify width and management on strip |
|
Buffer |
|
Specify number, whether strip at
bottom, for erosion or water quality control, width, strip management |
|
Rotational strip cropping |
|
Specify number, timing of rotation on
each strip |
|
Name and save |
Hydraulic Elements and
Their Sequence
|
|
|
|
Channels |
|
Specify grade |
|
Impoundments |
|
Nothing to specify |
|
Specific order of elements |
|
Name and save sequence |
System of Hydraulic
Elements
|
|
|
System composed of named sequence of
hydraulic elements |
|
Number of systems on hillslope |
|
Is the last one at the bottom of the
slope? |
|
Name and save systems |
Subsurface Drainage
Systems
|
|
|
|
|
Represented by: |
|
Hydrologic soil group for soil when it
is well drained |
|
Entered in soil input |
|
Fraction of area that is drained |
|
Name and save |
UNIT 6
LIMITS OF APPLICABILITY
|
|
|
|
How well does RUSLE apply to this
situation? |
|
Erosion Processes |
|
Land Uses |
|
Geographic Regions |
|
Temporal Scale |
|
Uncertainty in computed values |
APPLICABLE PROCESSES
|
|
|
Yes:
Interrill and rill erosion |
|
Yes:
Sediment yield from overland flow slope length |
|
Yes: Sediment yield from terrace
channels and simple sediment control basins |
|
No:
Ephemeral or permanent incised gully erosion |
|
No:
Stream channel erosion |
|
No:
Mass wasting |
Applicable Land Uses
|
|
|
All land uses where overland flow and
interrill-rill erosion occurs |
|
Land use independent |
|
Best: Cropland |
|
Moderate: Disturbed lands like military
lands, construction sites, landfills, reclaimed lands |
|
Acceptable: Rangelands, disturbed
forestlands, parks and recreational areas |
Cropland Applications
|
|
|
Best:
Clean tilled corn, soybean, wheat crops |
|
Moderate: Conservation tillage,
rotations involving hay |
|
Acceptable: Hay, pasture |
|
Most variable: Support practices,
especially contouring |
MOST APPLICABLE
GEOGRAPHIC REGIONS
|
|
|
Rainfall occurs regularly |
|
Rainfall predominant precipitation |
|
Rainfall exceeds 20 inches |
|
Northwest Wheat and Range Region (NWRR)
special case |
|
West problem area because of infrequent
storms |
APPLICABLE SOILS
|
|
|
Best: Medium Texture |
|
Moderate: Fine Texture |
|
Acceptable: Coarse Texture |
|
NO: Organic |
APPLICABLE TOPOGRAPHY
|
|
|
|
Slope Length |
|
Best:
50 - 300 feet |
|
Moderate: 0 - 50 ft , 300 - 600 ft. |
|
Acceptable: 600 - 1000 feet |
|
NO: >1000 feet |
APPLICABLE TOPOGRAPHY
|
|
|
|
Slope Steepness |
|
Best:
3 - 20% |
|
Moderate: 0 - 3%, 20 - 35% |
|
Acceptable: 35 - 100% |
|
NO: >100% |
UNCERTAINTY
|
|
|
Best (±25%): 4 < A < 30 t/ac/yr |
|
Moderate (±50%): 1 < A < 4 |
|
30 < A < 50 |
|
Least (>±100%):
A < 1 |
|
(>±50%): A > 50 |
Significant Change
|
|
|
|
Rule of thumb: |
|
A change in a RUSLE2 soil loss estimate
by more than 10% is considered significant and meaningful in terms of
representing main effect. |
|
An change less than 10% is not
considered significant in general |
|
The accuracy for RUSLE2 representing
how main effects affect soil loss is much better than the absolute accuracy
for RUSLE2 estimating soil loss at any particular location and landscape
condition. |
TEMPORAL APPLICABILITY
|
|
|
Best:
Average annual, average annual season, average annual single day |
|
Least:
Single storm provided great care used, generally not recommended |
|
|
Sensitivity
|
|
|
Change in soil loss per unit change in
a particular variable |
|
Select a base condition |
|
Vary input values for a variables about
base condition |
|
Sensitivity varies according to
condition |
|
Variables with greatest sensitivity
require greatest attention |
Examples of Sensitivity
|
|
|
|
Some variables have a linear effect |
|
Erosivity factor R |
|
Slope steepness |
|
Effect of most variables is nonlinear |
|
Ground cover |
|
Below ground biomass |
|
Roughness |
Examples of Sensitivity
(cont)
|
|
|
|
Low sensitivity |
|
Slope length at flat slopes (0.5%) A=
4.6 t/a at k
= 150 ft, 5.2 t/a at k = 500 ft, 5.5 t/a at k = 1000 ft |
|
Moderate sensitivity |
|
Slope length at steep slopes (20%) A =
129 t/a at k
= 50 ft, A = 202 t/a at k = 100 ft, A = 317 t/a at k = 200 ft. |
Examples of Sensitivity
(cont)
|
|
|
|
High sensitivity-Ground cover single
most important |
|
Adding mulch |
|
Most variables interrelated |
|
Ground cover at planting not as much as
expected |
|
Sequence of operations |
|
Effect of depth for a tandem disk |
|
Depends on whether proceeded by
moldboard plow |
SUMMARY
|
|
|
RUSLE varies in its applicability |
|
Results from RUSLE must be judged |
|
Degree of confidence in results varies |