1. Lecture 15 - 1 ERS 482/682 (Fall 2002) Erosion and sediment transport ERS 482/682 Small Watershed Hydrology

2. Lecture 15 - 2 ERS 482/682 (Fall 2002) Figure 7.1 (Brooks et al. 1991)

3. Lecture 15 - 3 ERS 482/682 (Fall 2002) Figure 15-1: Dunne & Leopold (1978)

4. Lecture 15 - 4 ERS 482/682 (Fall 2002) Figure 15-3: Dunne and Leopold (1978)

5. Lecture 15 - 5 ERS 482/682 (Fall 2002) Water erosion Figure 7.2 (Brooks et al. 1991) Rainfall intensity  Kinetic energy 

6. Lecture 15 - 6 ERS 482/682 (Fall 2002) Water erosion Surface runoff –Transports soil particles –Closes soil surface  increase surface runoff Rill erosion –Microchannels (50-300 mm wide; up to 300 mm deep) Sheet erosion (inter-rill erosion) –Movement of semi-suspended particles over land surface Gully erosion

7. Lecture 15 - 7 ERS 482/682 (Fall 2002) Gully erosion Figure 8.1 (Brooks et al. 1991)

8. Lecture 15 - 8 ERS 482/682 (Fall 2002) Pawnee Buttes, CO Knickpoint Gully erosion

9. Lecture 15 - 9 ERS 482/682 (Fall 2002) Figure 15-15: Dunne and Leopold (1978)

10. Lecture 15 - 10 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation whereA = soil loss (tons per acre) R = rainfall erosivity index K = soil erodibility index L = hillslope-length factor S = hillslope-gradient factor C = cropping-management factor P = erosion-control practice factor

11. Lecture 15 - 11 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Rainfall erosivity index, R –Depends on kinetic energy and rainfall intensity whereE = kinetic energy (ft ton ac -1 in -1 ) I 30 = maximum 30-minute intensity (in hr -1 ) n = total number of storms in period of interest

12. Lecture 15 - 12 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Rainfall erosivity index, R –Depends on kinetic energy and rainfall intensity Figure 15-16 (Dunne & Leopold 1978)

13. Lecture 15 - 13 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Soil erodibility factor, K –Average soil loss (per rainfall erosivity) when the soil is exposed as cultivated bare fallow under specified conditions of hillslope length and gradient

14. Lecture 15 - 14 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Soil erodibility factor, K Figure 7.4 (Brooks et al. 1991)

15. Lecture 15 - 15 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Length and slope factors, LS Figure 15-19 (Dunne & Leopold 1978)

16. Lecture 15 - 16 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Cropping-management factor, C –Examples from Dunne and Leopold (1978): Agricultural land (Table 15-2) Woodland (Table 15-3) Pasture, rangeland, and idle land (Table 15-4)

17. Lecture 15 - 17 ERS 482/682 (Fall 2002) Universal Soil-Loss Equation Erosion control practice factor, P –Varies with technique Table 15-5: Dunne and Leopold (1978)

18. Lecture 15 - 18 ERS 482/682 (Fall 2002) Modified USLE whereVM = vegetation management factor

19. Lecture 15 - 19 ERS 482/682 (Fall 2002) Figure 7.5 (Brooks et al. 1991) How high canopy is and how much canopy cover How much ground cover % of fine roots in ground

20. Lecture 15 - 20 ERS 482/682 (Fall 2002) Soil mass movement Downslope movement of finite masses of soil, rock and debris –Driven by gravity Figure 8.5 (Brooks et al. 1991)

21. Lecture 15 - 21 ERS 482/682 (Fall 2002) Figure 15-29 (Dunne and Leopold 1978)

22. Lecture 15 - 22 ERS 482/682 (Fall 2002) Pawnee Buttes, CO Rockfall Slump

23. Lecture 15 - 23 ERS 482/682 (Fall 2002) Figure 15-40: Dunne and Leopold (1978)

24. Lecture 15 - 24 ERS 482/682 (Fall 2002) Figure 15-41 (Dunne and Leopold 1978) Figure 8.5 (Brooks et al. 1991)

25. Lecture 15 - 25 ERS 482/682 (Fall 2002) Sediment yield Total sediment outflow from a watershed for a specific period of time at a defined point in the channel Expressed as: Weight per area per time or Volume per area per time kg ha -1 yr -1 m 3 ha -1 yr -1 tonne = 1000 kg

26. Lecture 15 - 26 ERS 482/682 (Fall 2002) Sediment transport Figure 9.1 (Brooks et al. 1991)

27. Lecture 15 - 27 ERS 482/682 (Fall 2002) Sediment transport Figure 9.2 (Brooks et al. 1991) Particles being picked up Particles being deposited

28. Lecture 15 - 28 ERS 482/682 (Fall 2002) Estimating sediment yield USLE Measuring suspended sediment concentrations Figure 7.1 (Stednick 1991)

29. Lecture 15 - 29 ERS 482/682 (Fall 2002) Estimating sediment yield USLE Measuring suspended sediment concentrations Figure 3.8A: Knighton (1998) Discharge  SS 

30. Lecture 15 - 30 ERS 482/682 (Fall 2002) Estimating sediment yield USLE Measuring suspended sediment concentrations Regress with discharge or turbidity (Lewis 1996) Does not account for bedload

31. Lecture 15 - 31 ERS 482/682 (Fall 2002) Estimating sediment yield USLE Measuring suspended sediment concentrations Lake/reservoir surveys Figure 3.8C and Figure 3.8D (Knighton 1998)

32. Lecture 15 - 32 ERS 482/682 (Fall 2002) Estimates of sediment yield Table 3.1 and Table 3.2 (Knighton 1998)

33. Lecture 15 - 33 ERS 482/682 (Fall 2002)