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Rock Weirs & Habitat Heterogeneity

Rock Weirs & Habitat Heterogeneity. Cache River. Cache Weirs. Installed in an attempt to save Heron Pond by: Raising stream bed elevation by depositing sediment Recent research indicates an overall loss of 2ft since 1996 Directing erosion away from Heron Pond

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Rock Weirs & Habitat Heterogeneity

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  1. Rock Weirs &Habitat Heterogeneity Cache River

  2. Cache Weirs • Installed in an attempt to save Heron Pond by: • Raising stream bed elevation by depositing sediment • Recent research indicates an overall loss of 2ft since 1996 • Directing erosion away from Heron Pond • Bank erosion continues at a rate of .10/ft per year • Stepping stream more gradually • Reducing stream power

  3. Fish ladders, locks and dams…….. The current trend in the WEST is to tear out as many of these as possible.

  4. Lots of Questions • Why are we putting hard structures into the stream? • How have the weirs affected the physical environment? • Have the weirs improved the hydrology? If so for how long?

  5. I thought I was interested in Hydrology And then research happened!

  6. Restoration Ecology • Efforts are often driven by very specific goals • Preservation of one species can have negative consequences on others • Variables are numerous • Action taken • Pre and post research is difficult to complete • Lack of funding • Too many variables • Lack of knowledge about pre disturbancelandscape and biology • Evaluation nonexistent or incomplete Decisions Research

  7. Cache Weirs • Weirs have been shown to increase Macroinvertebrate biomass but not biodiversity as the habitat heterogeneity hypothesis suggests (Walter & Wiles 2008) Heterogeneity Hyothesis (MacArthur & MacArthur 1961)

  8. Proposed strategy for sequencing stream rehabilitation techniques (Roni & Hanson, 2008)

  9. It’s a lot like…. Wildlife science: gaining reliable knowledge (Romesberg 1981) “Wildlife science must try the H-D method. Without it the ability to detect errors in pronouncements of laws, the self-correcting feature science must have, is fatally lacking. All learning takes place in a feedback system in which ideas and reality interplay. The method of retroduction coupled with the H-D method is such a feedback system. Uncouple them and the ability to learn, to tell error from truth, is hindered, if not destroyed.”

  10. Proposal • Are the two significantly different as assumed? • How much habitat heterogeneity is present at each location type? • Study physical habitat of weir and non-weir sites • Assess discharge • Bank width • Depth • Canopy cover, etc

  11. At the Cache • Restoration • Conservation • Preservation Complex overlap of disciplines- hydrology biology ecology: landscape restoration engineering economics Photo used without permission !

  12. The end

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