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Bed-material Sampling

Bed-material Sampling. May 2013 TESNAR Class Mackenzie Keith Hydrologist Oregon Water Science Center Portland, Oregon. The b-axis. From Bunte and Abt, 2001. Why measure bed material?. Sediment transport calculations and indications Fish/habitat /bio studies

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Bed-material Sampling

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  1. Bed-material Sampling May 2013 TESNAR Class Mackenzie Keith Hydrologist Oregon Water Science Center Portland, Oregon

  2. The b-axis From Bunte and Abt, 2001

  3. Why measure bed material? • Sediment transport calculations and indications • Fish/habitat /bio studies • Balance between supply and transport • Sediment attrition • Lithology

  4. What’s in a D50? Plotting and reading data • Bed material can range over several orders of magnitude • Log transformations and the phi scale • Reading and reporting D50 (or D16, D84, or whatever) • Looking at multiple sets of data

  5. Surface vs. Subsurface • Surface layer • Subsurface layer • Armoring ratio

  6. Techniques for coarse material sampling: The grains • Operator bias • Which side is the b-axis? • Results from yesterday • How many clasts do I count? • What if I can’t pick the clast up? • Surface • Subsurface

  7. Techniques for coarse material surface sampling: The counts • Facies mapping • Wolman pebble counts • Sampling frames • Ocular assessments • Photogrammetric techniques • Zig-Zag • Bank to bank • Other aquatic habitat measures

  8. Techniques for coarse material surface sampling: Longitudinal • Choosing the right location • Choosing the right spacing • Choosing the right grain • Tiny clasts? • Giant clasts?

  9. A method for subsurface sampling: Bulk sampling • Clearing the surface layer • Digging, sieving, and weighing • How much to dig up? • Filling in the hole

  10. Let’s go do a pebble count! • Siletz gravel bar • Fill out forms • Measure and record gravel • Discuss subsurface sampling

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