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Flood rings: Paleoflood evidence in tree-ring anatomy

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In low-gradient, low energy rivers, forms of tree-ring evidence such as impact scars or stem deformation do not provide useful evidence of past floods. In this talk, I explain the strengths and limitations of wood anatomy as tools in in paleoflood hydrology.

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Flood rings: Paleoflood evidence in tree-ring anatomy

  1. 1. Development of a Framework for Technical Review of Paleoflood Information | Rockville, Maryland | May 29-30, 2019 PALEOFLOOD EVIDENCE IN TREE-RING WOOD ANATOMY FLOOD RINGS
  2. 2. CRATER LAKE, OREGON
  3. 3. THE GLOBAL TREE-RING NETWORK INCLUDES DATA FROM THOUSANDS OF LOCATIONS, BUT MOST (ALL?) OF THESE TREES ARE NOT AFFECTED BY FLOODING! Source: St. George, Past Global Changes Magazine, 2014
  4. 4. ? HOW DOES ONE DETERMINE SPECIFIC FLOODS FROM TREE RINGS?
  5. 5. SCARRING DUE TO IMPACT OR ABRASION
  6. 6. ROBERT SIGAFOOS (1920-1995) UNITED STATES GEOLOGICAL SURVEY
  7. 7. Source: NDSU Ag Comm
  8. 8. TILTING OR UPROOTING BY HYDRAULIC PRESSURE
  9. 9. PALEODISCHARGE ESTIMATES STRUCTURAL ENGINEERING
  10. 10. Source: Ballesteros et al., Journal of Hydrology, 2015 TILTED TREES GROWING IN FLOODPLAINS EXHIBIT REACTIONS CAUSED BY FLOODS, AND THEIR STRUCTURAL BEHAVIOR MAY BE LINKED TO FLOW CONDITIONS.
  11. 11. HIGH-GRADIENT RIVERS Source: Uday Kunwar Thapa, University of Minnesota
  12. 12. Source: Greg Brooks, Geological Survey of Canada LOW-GRADIENT RIVERS
  13. 13. WOOD ANATOMY
  14. 14. DECIDUOUS TREES GROWING ON THE POTOMAC RIVER FLOOD PLAIN NEAR WASHINGTON, D.C. ARE OCCASIONALLY FLOODED DURING THE GROWING SEASON. IF CROWNS ARE DAMAGED, THE SUBSEQUENT RADIAL GROWTH OF STEMS PRODUCES WOOD THAT IS OFTEN ANATOMICALLY DIFFERENT FROM THAT OF UNDAMAGED TREES. “ ” Tom Yanosky USGS Professional Paper 1296, 1983
  15. 15. ANNUAL GROWTH RINGS IN RIPARIAN TREES THAT CONTAIN UNUSUAL WOOD ANATOMICAL FEATURES CAUSED BY INUNDATION OR DEFOLIATION DUE TO FLOODING.
  16. 16. 1997 Source: Dr. Greg Brooks, Geological Survey of Canada
  17. 17. GRAND FORKS, NORTH DAKOTA
  18. 18. Source: Dr. Greg Brooks, Geological Survey of Canada WINNIPEG, CANADA
  19. 19. QUERCUS
  20. 20. √ 24 OAK TREE RINGS (NORMAL ANATOMY) 18
  21. 21. Source: Mike Rastiello
  22. 22. OAK TREE RINGS (ANATOMY DISRUPTED BY FLOODING)
  23. 23. FLOOD RINGS EXTENDED THE EVENT RECORD FOR THE RED RIVER OF THE NORTH BACK TO THE MID-1600S. Source: St. George and Nielsen, The Holocene, 2003
  24. 24. 1826
  25. 25. STEM POSITION
  26. 26. WOOD ANATOMICAL SIGNATURES CAUSED BY FLOODING ARE MOST PROMINENT NEAR THE ROOT AND DISAPPEAR UP THE STEM. Source: St. George et al., Tree-Ring Research, 2002
  27. 27. PHENOLOGY/ TIMING
  28. 28. Source: Paul Copini, Wagenegin University EXPERIMENTAL FLOODING
  29. 29. FLOODING CAUSES OAKS TO FORM NARROW EARLYWOOD VESSELS, BUT ONLY IF IT OCCURS AFTER BUDSWELL OR INTERNODE EXPANSION. Source: Copini et al, , Frontiers in Plant Science, 2016
  30. 30. CENSORING/ SCREENING
  31. 31. THE GROWTH LOCATION OF TREES ACTS TO CENSOR SMALLER FLOODS FROM ANY POTENTIAL RECORD DERIVED FROM WOOD ANATOMY.
  32. 32. ALL FLOOD RINGS
 ARE CAUSED BY MAJOR FLOODS NOT ALL MAJOR FLOODS CAUSE OAKS TO FORM FLOOD RINGS
  33. 33. ALTHOUGH THE TREE-RING PALEOFLOOD RECORD HAS EXCELLENT TEMPORAL RESOLUTION AND GOOD OVERALL SUCCESS AS A TOOL IN IDENTIFYING PAST EXTREME FLOODS, IT IS EFFECTIVELY A MINIMUM ESTIMATE OF BOTH FLOOD FREQUENCY AND MAGNITUDE. “ ” St. George and Nielsen, The Holocene, 2003
  34. 34. FLOOD RINGS
  35. 35. OAK FORESTS IN NORTH AMERICA Source: Report on Forests of North America (Exclusive of Mexico), 1884
  36. 36. @sco stgeorge

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