1. 1 Erosion and Sedimentation Processes, Factors and Impacts on the Environment Issued May 2009 Level IA: Fundamentals Seminar Education and Training Certification Requirements for Persons Involved with Land Disturbing Activities

2. 2 OVERVIEW Introduction of Erosion and Sedimentation (E&S) –Definitions and general stages of E&S –Basic processes and factors governing E&S –Natural erosion vs. accelerated erosion Impacts of Erosion and Sedimentation (E&S) –Environmental impacts –Economic impacts

3. 3 EROSION - The process by which the land surface is worn away by the action of water, wind, ice and gravity

4. 4 Predevelopment Construction

5. 5 Photograph of erosion Water Erosion

6. 6 Types of Water Erosion 1. Splash Erosion 2. Sheet Erosion 3. Rill Erosion 4. Gully Erosion

7. 7 Raindrop impact on bare soil. Splash Erosion

8. 8 Sheet Erosion

9. 9 Photograph of rill erosion RILL EROSION

10. 10 Photograph of gully erosion Gully Erosion

11. 11 Insert picture here SPLASH SHEET RILL & GULLY STREAM & CHANNEL TYPES OF WATER EROSION

12. 12 Sedimentation The process by which the eroded material is transported and deposited by Water Wind Ice Gravity

13. 13 Photograph of sediment SEDIMENTATION

14. 14 SEDIMENT TRANSPORT GA stream following 1/2” of rain June 26, 2001

15. 15 Stages in Erosion & Sedimentation 1. Detachment2. Transport3. Deposition

16. 16 Natural Erosion vs. Accelerated Erosion

17. 17 Natural (Normal) Erosion Erosion without the interference of man’s activities. The rate is generally small except for stream channel and shore erosion.

18. 18 Accelerated Erosion Erosion intensified by human activities – Example: Farming – Example: Construction

19. 19 Expected Erosion Rates (Tons/Acre/Year) 1. Forest Land 1 or greater 2. Farm Land 15 or greater 3. Construction Sites 100 or greater

20. 20 Impacts of Construction Activities 1. Removal of soil organic matter 2. Removal of vegetation 3. Reshaping of ground surface contours 4. Exposure of subsoil 5. Changing the pervious ground surface to impervious

21. 21 Factors Affecting Erosion 1. Climatic (rainfall and runoff) Factors 2. Soil Factors 3. Topographic Factors 4. Vegetative Factors

22. 22 RAINDROP IMPACT & SPLASH EROSION

23. 23 The potential for soil erosion varies during the year in GA We have more thunderstorms in the summer

24. 24 Percent Energy

25. 25 Photograph of river VOLUME AND VELOCITY OF FLOW

26. 26 Topography SLOPE GRADIENT SLOPE LENGTH Gradient is expressed as number of horizontal units per unit vertical such as 3 to 1 or 4 to 1 or in percentage as 33 percent or 25 percent.

27. 27 Slope Gradient 4 to 1 or 4:1 means that four feet of horizontal length are required for each foot of vertical change in elevation 1’ 4’

28. 28 Slope Gradient

29. 29 Soil Factors Fine sandy & silty soils are more erodible than clay type soil & those with higher percentage of organic matter.

30. 30 Vegetative Factors Absorbs raindrop impact Reduces detachment Roots hold soil in place Slows water flow Adds organic material to the soil Reduces runoff Increases infiltration

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32. 32 Photograph of vegetation holding soil in place Vegetation holds soil in place

33. 33 Photograph of vegetation slowing water and trapping sediment Vegetation slows the flow of water, reducing erosion and trapping sediment

34. 34 Photograph rate and speed of runoff Rate and speed of runoff

35. 35 Photograph

36. 36 Vegetation provides organic material

37. 37 Impacts of Erosion and Sedimentation 1. Loss of soil productivity 2. Adverse effects on other water resource facilities 3. Loss of reservoir storage capacity 4. Flood impacts 5. Recreational impacts 6. Deterioration of water quality

38. 38 Increased maintenance costs for stormwater management systems

39. 39 Decreased Recreational Value

40. 40 Biological impacts Screens Out Sunlight = Decline in Plant Growth

41. 41 ECOSYSTEM Sedimentation Disrupts The Ecosystem

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45. 45 SUMMARY Many processes and factors are involved in erosion and sedimentation Erosion is a natural process, but it can be accelerated by human activities. KEEP BARE SOIL TO AN ABSOLUTE MINIMUM! Impacts of erosion and sedimentation can be devastating to both the environment and the economy

46. 46 Georgia Soil and Water Conservation Commission State Office 706.542.3065 Certification 706.542.1840 www.gaswcc.georgia.gov

47. 47 QUESTIONS?