Evaluating Soil Loss Using RUSLE PDF

Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Evaluating Soil Loss Using RUSLE Site Condition: A disturb...

Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Evaluating Soil Loss Using RUSLE Site Condition: A disturbed area of 15 acres has been created due to development construction near Norwich, Conn. (R=150). The soil is Charlton exposed in the B horizon. The average slope is 8% and the length of the slope is 400 feet. EnviroCert International, Inc.TM 17 Problem 1 Determine the estimated soil loss from this site if it remains unprotected for a period of one year. EnviroCert International, Inc.TM 18 9-9 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Use RUSLE Equation A = R K LS C P First find R-value using isoerodent maps EnviroCert International, Inc.TM 19 Reference Isoerodent maps from Figure 9-1 A = R K LS C P First find R-value using isoerodent maps EnviroCert International, Inc.TM 20 9-10 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Reference Isoerodent maps from Figure 9-1 R=150 EnviroCert International, Inc.TM 21 A = 150 K LS C P Now solve for soil erodibility factor, K. Reference Table 9-1 matching soil types EnviroCert International, Inc.TM 22 9-11 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 K-Value Table 9-1 K= 0.43 EnviroCert International, Inc.TM 23 A = 150.43 LS C P Find the corresponding slope length value, LS from slope grade and length Determine LS-value from Table 9-2 EnviroCert International, Inc.TM 24 9-12 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Table 9-2 Length = 400 ft. Slope = 8% LS value = 2.7 EnviroCert International, Inc.TM 25 A = 150.43 LS C P Determine plant cover management factor, C. Use Table 9-3 to determine C-value EnviroCert International, Inc.TM 26 9-13 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Table 9-3 C-value = 1 C-value = 1 (assume 1 if no cover practice provided) EnviroCert International, Inc.TM 27 A = 150.43 LS C P Finally, determine support practice factor, P Refer to P-factors Table 9-4 EnviroCert International, Inc.TM 28 9-14 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Table 9-4 P-value = 1 (assume 1 because of unprotected land) EnviroCert International, Inc.TM 29 Problem 1 - Solution A = R K (LS) C P A = (150)(0.43)(2.70)(1)(1) = 174.15 tons/acre/year x 15 acres = 2,612 tons per year EnviroCert International, Inc.TM 30 9-15 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Partial Year Soil Loss M Factor Table 9-6 Table 9-6 EnviroCert International, Inc.TM 31 Problem 2 Given the rainfall intensity distribution for Connecticut as shown on Table 9-6, determine the soil loss from this site for the period from October 1 to June 1 the following season. EnviroCert International, Inc.TM 32 9-16 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Soil Loss Percentages Percentages are 8 + 8 + 7 + 3 + 3 + 5 + 4 + 6 from Table 9-6 EnviroCert International, Inc.TM 33 Problem 2 - Solution Table 9-6 for October 1 through June 1: 8+8+7+3+3+5+4+6 = 44% of annual soil loss 0.44 x 2,612 = 1,149 tons EnviroCert International, Inc.TM 34 9-17 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Problem 3 Determine the annual soil loss from this site if a temporary seeding of annual rye grass is established. EnviroCert International, Inc.TM 35 What Value Changes? A = 150.43 2.7 C P C-value will decrease with ground cover. EnviroCert International, Inc.TM 36 9-18 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Table 9-3 C-value decreases by a factor of 10 EnviroCert International, Inc.TM 37 Problem 3 - Solution Table 9-3 for Temporary Seeding, annual rye: C = 0.1 0.1 x 2,612 = 261 tons EnviroCert International, Inc.TM 38 9-19 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Problem 4 How many cubic yards of soil will be lost from this site if the site is left unprotected for a year and the surface is compact and smooth, scraped with a bulldozer uphill and downhill? EnviroCert International, Inc.TM 39 Now What Will Change? A = 150.43 2.7 C P Support factor P will increase. (Table 9-4) EnviroCert International, Inc.TM 40 9-20 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Table 9-4 P-value = 1.3 EnviroCert International, Inc.TM 41 Problem 4 - Solution P = 1.3 So, predicted soil loss is recalculated: 2,612 x 1.3 = 3,396 tons 1st of 2 methods to convert tons to cubic yards: 3,396 Tons x 0.7 = 2,377 cubic yards (Table 4-5 for conversion factors) EnviroCert International, Inc.TM 42 9-21 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Unit Weight of Soil TABLE 9-5 - ESTIMATED WEIGHT OF SOILS 1 EnviroCert International, Inc.TM 43 Problem 4 - Solution Table 9-1 - Charlton texture is a fine sandy loam Table 9-5 - fine sandy loam has a unit weight of 1 0 5 l b s. / f t 3 2nd of 2 methods to convert tons to cubic yards: unit weight = 105 lbs./ft3 EnviroCert International, Inc.TM 44 9-22 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Problem 4 - Solution How many cubic yards? Convert 3396 tons to cubic yards using 105 lbs./ft3 (3396 tons)(2000 lbs./ton)(ft3/105 lbs.)(cy/27 ft3) = 2396 cy EnviroCert International, Inc.TM 45 Problem 5 A 22-acre site in Syracuse, NY (R=100) on Paxton soils is under construction. The site lies on a 6% slope with a slope length of 1,000 feet. (a) If left unprotected from April 1 until Nov. 1, what is the expected soil loss from the project based on the erosion index percentage graph (Figure 9-8)? (b) If mulched with straw at 2 tons per acre, what is the expected soil loss? EnviroCert International, Inc.TM 46 9-23 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Problem 5 - Solution A = R K (LS) C P A = (100)(0.43)(3.30)(1)(1) x 22 acres = 3,122 tons per year EnviroCert International, Inc.TM 47 Problem 5 – Solution (a) Next, adjust for the period of construction: Use the Erosion Index Graph Figure 9-8: 94% (Nov. 1) - 4% (Apr. 1) = 90% EnviroCert International, Inc.TM 48 9-24 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Problem 5 – Solution (b) Next, adjust for the period of construction: Table 9-3 for 2 tons per acre straw mulch: C-value = 0.02 (2,810) (0.02) = 56 tons EnviroCert International, Inc.TM 49 Modified Universal Soil Loss Equation (MUSLE) T = 95(V Qp)0.56 K LS C P Where: T = Sediment yield in tons for a storm event V = Volume of runoff for the storm event, ac-ft Qp = Peak flow for the storm event, cfs K, LS, C, P = same as in RUSLE For a specific storm event EnviroCert International, Inc.TM 50 9-25 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 Problem 6 Based on the 15 acre site in Problem 1, find the sediment yield for a storm with a Qp = 1.56 cfs and Runoff = 2.07” T = 95(V Qp)0.56 K LS C P K = 0.43; LS = 2.7; C = 1.0; P = 1.0 V = Runoff volume in ac-ft EnviroCert International, Inc.TM 51 Problem 6 Approach? Use the MUSLE Equation anytime you are calculating SOIL YIELD for a specific rain event at a specific location. Important note: Keep your notes organized. Label the question number and values. EnviroCert International, Inc.TM 52 9-26 | Page  Certified Professional in Erosion and Sediment Control Review Presentation Manual V.7.0 T = 95(V Qp)0.56 K LS C P V = Runoff Acres (or [2.07in 1ft/12in] 15 Ac) = 2.59 ac-ft T = 95(V Qp)0.56 K LS C P T = 95(2.59 1.56)0.56 0.43 2.7 1 1 T or Sediment Yield for this storm event equals: 241 tons EnviroCert International, Inc.TM 53 Wind Erosion The process in which, by the actions of wind, a soil particle is detached and removed from its location. EnviroCert International, Inc.TM 54 9-27 | Page