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REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) for Construction Sites

REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) for Construction Sites. Predicting Soil Erosion By Rainfall and Overflow Presented by: Guangyan Griffin, P.E., Northern Region Construction Alaska Department of Transportation and Public Facilities

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REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) for Construction Sites

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  1. REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE)for Construction Sites Predicting Soil Erosion By Rainfall and Overflow Presented by: Guangyan Griffin, P.E., Northern Region Construction Alaska Department of Transportation and Public Facilities T2 Research Project

  2. OBJECTIVES • Understand erosion processes • Learn RUSLE and its factors • RUSLE’s application on construction sites

  3. Erosion and Sedimentation Erosion is a process of detachment and transport of soil particles by erosive agents. • Erosive Agents • Raindrop impact • Overland flow surface runoff from rainfall Sedimentation is the deposition of eroded material.

  4. FACTORS AFFECTING EROSION • Climate • Soil • Topography • Land use • Cover • Supporting practices

  5. EROSION IS A CONCERN • Degrades soil resource • Causes downstream sedimentation • Produces sediment which is a pollutant • Produces sediment that carries pollutants

  6. EROSION PREDICTION AS A TOOL • Evaluate impact of erosion prior to construction • Manage BMPs more effectively and economically • Doing it right the first time • Serve as technical rationale • Concept: • Estimate erosion rate under different conditions

  7. OVERVIEW OF RUSLE • RUSLE background • Where RUSLE applies • RUSLE factors

  8. RUSLE HISTORY BACKGROUND • Zingg’s equation (1940) • Smith and Whitt’s equation (1947) • US Dept. of Agriculture: Agri. HandBooks • AH-282 (1965) – USLE, Wischmeier and Smith • AH-537 (1978) – Wischmeier and Smith • AH-703 (1997) – RUSLE, Renard and Froster • Office of Surface Mining Manual (mined, reclaimed land, construction sites) (1998) • Computer software: - RUSLE1 (1992) - RUSLE2 (2001)

  9. RUSLE BACKGROUND • From the theory of erosion process that the soil loss is caused by rain drop impact and the overland flow. • Consists of a set of mathematical equations

  10. RUSLE APPLICATIONS • Cropland • Pastureland • Rangeland • Disturbed forest land • Construction sites • Surface mine reclamation • Military training lands • Parks • Waste disposal/landfills

  11. RUSLE Area Landscape Overland flow Interrill Rill Gully (Concentrated flow)

  12. RUSLE FACTORSA = R K L S C P • R- Rainfall-runoff erosivity factor • K- Soil erodibility factor • L- Slope length factor • S- Slope steepness factor • C- Cover-management factor • P- Supporting practices factor

  13. EROSIVITY - R • 22 years or longer rainfall data gathered by weather stations. • Single storm • Energy x 30 minute intensity • Annual-sum of daily values • Average annual-average of annual values • Monthly value=average annual x fraction that occurs on a given month

  14. EROSIVITY - R Measure of erosivity of climate at a location Las Vegas, NV 8 Phoenix, AZ 22 Anchorage, AK 26 Denver, CO 40 Fairbanks, AK 48 Syracuse, NY 80 Juneau, AK 101 Minneapolis, MN 110 Chicago, IL 140 Richmond, VA 200 Dallas, TX 275 Birmingham, AL 350 Charleston, SC 400 New Orleans, LA 700

  15. R-factor for Alaska • Retrieved from USDA RUSLE2 computer program data file at fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Index.htm. • AK is broken into climate zones per common resource areas (CRA) • Way to acquire an R-Factor: • Determine the climate zone ID in which the construction project is located from the map • Look up the R-factor from the table

  16. SOIL ERODIBILITY - K • Measure of K-factor under standard unit plot condition • 72.6 ft long, 9% slope, tilled continuous fallow, up and down hill tillage • Represent the uniform soil at upper 6”of the subsoil (not topsoil) in a construction site • Major factors • Texture • Organic matter • Structure • Permeability

  17. Obtain Soil Data • Perform gradation analysis • sand • silt • clay Options: • Information in Alaska Soil Survey Report published by NRCS. • Using soil-erodibility nomograph chart or equation. • Use regression equations in AH-703, Renard et al. (1997).

  18. Approximate K Values for Construction Soil Material

  19. TOPOGRAPHY - LS • Slope length (L) and steepness (S) are major factors • Watershed topography affects erosion rate and sediment transport • Steep slopes typically result in rapid runoff • Long slopes acuminate more runoff

  20. Hillslope Shape Convex Uniform Complex-Convex:concave Complex-Concave:convex Concave

  21. Slope Length for Uniform Slope SOIL LOSS SEDIMENT YIELD SLOPE LENGTH RUSLE ESTIMATES TO HERE

  22. Slope Length for Complex Slope Soil loss Deposition Sediment yield SLOPE LENGTH

  23. Values for LS for Construction Sites

  24. LS Factor for Complex Slope • break it down into several fairly uniform segments where the gradient changes, preferably into equal lengths

  25. Cover Management Factor C • The factor representing the site’s cover protection from rainfall impact. • The ratio of erosion between a specific ground cover and bare ground.

  26. Cover-Management Effects Raindrops intercepted by canopy cover Raindrops not intercepted by canopy cover Canopy cover Intercepted rainfall falling from canopy cover Ground cover Ridges Buried residue Live roots Dead roots

  27. Erosion Control Technology Council (ECTC)http://www.ectc.org/ • Industry authority in the development of standards, testing, and installation techniques • Rolled erosion control products (RECPs), • Hydraulic erosion control products (HECPs) • Sediment retention fiber rolls (SRFRs).

  28. C-factor for Other Covers (Pitt, Clark and Lake, 2007; Fifield, 2004)

  29. Mulch (Mechanical) and Rock Cover (Wischmeier and Smith, 1978)

  30. Supporting Practices (P) Conservation practices are controllable, experience-driven and interactive measures. They can: enhance the factors of cover and soil texture mitigate the influence of rainfall and runoff modify flow path length and steepness

  31. Supporting Practices • Strips/barriers • Buffer strips, • Filter fence, • Wattles • Straw bales, • Gravel bags • Diversions • Channel • Terrace • Impoundments • Sediment traps • Detention / retention pond

  32. P-factor for Construction Sites (Fifield 2004 and Foster & Toy 1998)

  33. Examples Steese Hwy R=31 Silty gravel (GM) K=0.17 80 % passing #10 35% passing #200 2.5:1 Slope/60 ft long LS=4.9 RKLS = 26 Tons/acre/yr

  34. Examples • C=1, up and down slope trackwalking P= 0.9 • 70% perennial grass cover C=0.0275, P =1 • Mulching C=0.02, tracked P=0.9 CP x RKLS = 0.9x26 = 23 Tons/acre/yr CP x RKLS = 0.0275x26 = 0.7 Tons/acre/yr CP x RKLS = 0.02x0.9x26 = 0.5 Tons/acre/yr

  35. Examples Valdez R=80 Silty gravel (GM) K=0.17 80 % passing #10 35% passing #200 2.5:1 Slope/60 ft long LS=4.9 RKLS = 67 Tons/acre/year

  36. Examples • C=1, up and down slope trackwalking P= 0.9 • 70% perennial grass cover C=0.0275, P =1 • Mulching C=0.02, tracked P=0.9 CP x RKLS = 0.9x67 = 60 Tons/acre/yr CP x RKLS = 0.0275x67 = 1.8 Tons/acre/yr CP x RKLS = 0.02x0.9x67 = 1.2 Tons/acre/yr

  37. SUMMARY • RUSLE is only for interrill and rill erosion, not for gully and channel erosion. • The result from RUSLE is estimated soil loss rate, cannot be interpreted as actual soil loss rate. • RUSLE AK use on unfrozen soil only

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