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Natural and Anthropogenic Agents of Watershed Change

Natural and Anthropogenic Agents of Watershed Change

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Natural and Anthropogenic Agents of Watershed Change

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  1. Natural and Anthropogenic Agents of Watershed Change

  2. Natural Agents of Watershed ChangeFloods The San Antonio River and Guadalupe River converge during a flood.

  3. Natural Agents of Watershed ChangeDrought Brummetts Creek in southern Indiana following 8 weeks without measurable rain.

  4. Natural Agents of Watershed ChangeFire

  5. Natural Agents of Watershed ChangeHurricanes

  6. Natural Agents of Watershed ChangeErosion and Sediment Deposition How much is natural??

  7. Timber Harvesting • Sediment production from logging roads is 770-fold higher than unlogged forests • 30% due to surface erosion • 70% due to mass soil failure

  8. Agricultural Impacts • Channelization • Drainage tiles • Removal of riparian vegetation • Tillage practices • Nutrient loss • Soil loss

  9. Indiana Drainage Code • Enacted by state legislature in 1965 • Co. Drainage Boards and Co. Surveys have authority • Must ‘maintain’ regulated drains in county • Code specifies that all vegetation may be removed for proper operation of the drain

  10. Legal Drain Cleaning ‘Uncleaned’ ‘Cleaned’

  11. IBI and Habitat Score vs. % Forest Land Cover From: Wang et al. 1997, for 134 sites on 103 WI streams

  12. IBI scores vs. Four Categories of Land Use. Correlations with agriculture and forest were statistically significant. From: Roth et al. 1996 in Michigan watershed – at 23 1st – 3rd order stream sites

  13. Potential Downstream Influences on Upstream Communities From: Pringle, 1997)

  14. The Problem: Sediment Deposition • Human disturbance causes sediment deposition in streams • Habitat degraded • Decline in biotic integrity of stream • Restoration needed

  15. David Starr Jordan(IU President: 1885-1891) • Earliest published comment on the destructive effects of sediments in streams (1889) • Wrote about loss of trout habitat in Colorado due to mining

  16. Hydrology of Sediment Transport

  17. Hydrology of SedimentTransport

  18. The Effects of Sedimentation • Habitat • substrate for plants • loss of benthic habitats • Macroinvertebrates • (60%< if TSS >120 mg/L over norm – Gammon, 1970) • interference with respiration • gilled macroinvertebrates • smothering • loss of interstitial space

  19. The Effects of Sedimentation Fishes • interference with respiration • gill clogging • 53-77% > in O2 consumption • loss of rearing habitat • emergence • visual impairments for feeding • move downstream to avoid sluicing (4.3 km)

  20. Moving Sediment DownstreamFlushing Flows • Regulated Streams (dams) • General Uses • One time sediment release • Regular maintenance of regulated streams • Benefits • Flushing out fines • Channel maintenance • Riparian habitat maintenance

  21. Glen Canyon Dam Controlled Release of 1996 • Max Q with dam = 34,000cfs • Ave. peak flow w/o dam = 93,400 cfs • Released 45,000 cfs for 7 days

  22. The Fawn River

  23. The Fawn River – Study Sites

  24. Study Sites – DNR Dam

  25. Study Sites – 750 W

  26. Study Sites – Rock Dam

  27. DNR Dam Release • May 18, 1998 - Sluicing Event • Increased sediment flow • Anoxic pulse

  28. The Fawn River * measured 6 days after a discharge event

  29. Suspended Sediments

  30. Sediments were deposited up to 3 feet deep

  31. The formerly pristine Fawn River was a sludgy mess

  32. Greenfield Mills - before Greenfield Mills - after

  33. Mussels were clogged and smothered

  34. Macroinvertebrates

  35. Fish Data • No live fish observed 5/19/98 • 27 dead fish observed at Rock Dam in 30 minutes • Dead fish had blackened gills • all adult fish

  36. Many of the dead fish had blackened gills

  37. Dead Fish @ Rock Dam

  38. Options For Restoration and Enhancement • Options for sediment removal. • Moving sedimentsdownstream • Remove them from the system

  39. Moving Sediments Downstream • Natural flow fluctuation • Flushing flows • Habitat alteration (In-stream structures)

  40. Moving Sediment Downstream:Natural Flow Fluctuation • Unregulated streams • After temporary discharge • Example:Valley Creek, Minnesota (Waters 1992) • Deposition decimated trout and invertebrates • 2 years of natural flow variation eventually cleaned bed • Trout and invertebrates recovered

  41. Moving Sediment DownstreamFlushing Flows • What flow regime to use? • How big (magnitude)? • How long (duration)? • When (timing)? • Comprehensive summary of techniques: Reiser et al (1985) for the Pacific Gas and Electric Co.

  42. Moving Sediment DownstreamFlushing Flows Magnitude • Three primary approaches • Hydrological • Use runoff records (200% mean annual Q) • Morphological • Use channel characteristics (1.5 year flood) • Sedimentological • Based on sediment transport equations

  43. Moving Sediment DownstreamFlushing Flows • Timing • Fish and wildlife requirements • Spawning: biological cue, floodplain spawners • Rearing: juveniles in the floodplain • Riparian vegetation • Historical runoff period • Water availability

  44. Moving Sediment DownstreamFlushing Flows Considerations • Downstream effects • Sediments downstream • Disturbance of spawning gravel • Speed of flow release and recession • Quality of flush water • *Most successful in high gradient and riffles*

  45. Moving Sediment DownstreamIn-stream Structures • Most tested techniques • Used commonly for trout • Macroinvertebrates & other organisms benefit • Localized scouring • Goals for use of in-stream structures • Speed current and increase turbulence • Deepen channel • Increase substrate particle size

  46. Moving Sediment DownstreamIn-stream Structures • Techniques for localized scouring • Placement of roughness elements in stream • Wing deflectors • Temporary structures

  47. Moving Sediment DownstreamIn-stream Structures • Roughness elements • Boulders, stones and logs • Increase scour • Turbulence • Velocity • Habitat creation

  48. Moving Sediment DownstreamIn-stream Structures

  49. Moving Sediment DownstreamIn-stream Structures • Wing Deflectors • Triangular, embedded in bank, angled downstream • Narrow and deepen stream • Increase velocity and scouring

  50. Moving Sediment DownstreamIn-stream Structures