1 / 50

Erosion and Sedimentation Processes, Factors and Impacts on the Environment

Erosion and Sedimentation Processes, Factors and Impacts on the Environment. Level IB: Advanced Fundamentals Seminar Education and Training Requirements for Individuals Involved in Land Disturbing Activities. Issued May 2009. OVERVIEW. Introduction of Erosion and Sedimentation (E&S)

hyman
Télécharger la présentation

Erosion and Sedimentation Processes, Factors and Impacts on the Environment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Erosion and Sedimentation Processes, Factors and Impacts on the Environment Level IB: Advanced Fundamentals Seminar Education and Training Requirements for Individuals Involved in Land Disturbing Activities Issued May 2009

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

  4. Predevelopment Construction

  5. Photograph of erosion Water Erosion

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

  7. Raindropimpact on bare soil Splash Erosion .

  8. Sheet Erosion

  9. Photograph of rill erosion RILLEROSION

  10. Gully Erosion Photograph of gully erosion

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

  12. Sedimentation The process by which the erodedmaterial istransportedanddepositedby • Water • Wind • Ice • Gravity

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

  14. Photograph of sediment SEDIMENTATION

  15. Stages in Erosion & Sedimentation 1. Detachment 2. Transport 3. Deposition

  16. Natural Erosion vs. Accelerated Erosion

  17. Natural (Normal) Erosion Erosionwithout theinterference of man’s activities. The rate is generally small except for stream channel and shore erosion.

  18. Accelerated Erosion Erosionintensifiedby human activities Example: Farming Example: Construction

  19. Estimation of Average Annual Soil LossRevised Universal Soil Loss Equation(RUSLE) A = R K S L C P A:Average Annual Soil LossR:Rainfall Erosivity Factor K:Soil Erodibility FactorS:Percent Slope L:Length of Slope C:Cover Management Factor P:Conservation Practice Factor

  20. RUSLE ExampleA = RKLSCP Given:Clarke County (R = 275)Table B-2.1 Cecil sandy loam (K = 0.28)Soil Survey 2:1 slope, 20 feet long (LS = 7.97)Table B-2.2 20% grass cover (C = 0.2)Table B-2.5 No other conservation practices(P = 1.00) Find:Soil loss for the given conditions. A = 122.7 tons per acre per year *Information taken from the Manual for Erosion and Sediment Control in GA

  21. RUSLE ExampleA = RKLSCP If youreduce the slope steepnessto 3:1 (LS = 4.93) … A = 75.9 tons/acre/year, a38%reduction in soil loss. or If youincrease the vegetative coverto 80% (C = 0.013) … A = 8.0 tons/acre/year, a94%reduction in soil loss.

  22. Expected Erosion Rates(Tons/Acre/Year) 1. Forest Land 1or greater 2. Farm Land 15or greater 3. Construction Sites100or greater

  23. Impacts of Construction Activities 1. Removal oforganic soil matter 2. Removal ofvegetation 3. Reshaping of groundsurface contours 4. Exposure ofsubsoil 5. Changing theperviousground surface toimpervious

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

  25. RAINDROP IMPACT & SPLASH EROSION

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

  27. Percent Energy

  28. Photograph of river VOLUME AND VELOCITY OF FLOW

  29. 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.

  30. 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

  31. Slope Gradient

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

  33. 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

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

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

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

  37. Photograph

  38. Vegetation provides organic material

  39. Impacts of Erosion and Sedimentation 1. Loss ofsoil productivity 2. Adverse effects on otherwater resource facilities 3. Loss ofreservoir storagecapacity 4.Floodimpacts 5.Recreationalimpacts 6. Deterioration ofwater quality

  40. Increased maintenance costs for stormwater management systems

  41. Decreased Recreational Value

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

  43. ECOSYSTEM Sedimentation Disrupts The Ecosystem

  44. 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

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

  46. QUESTIONS?

More Related