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Expecting the unexpected: The relevance of old floods to modern hydrology

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As one of the most destructive hazards on our planet, floods kill thousands of people and cause billions of dollars in property damage every year. We usually try to gage the risk of future floods by fitting mathematic functions to hydrological data and then extrapolating the upper tail of those distributions. But because large floods are rare and river gage records are short, the conventional approach can sometimes drastically underestimate the threat posed to communities and infrastructure by extreme floods. In this lecture, I’ll argue that paleoflood hydrology — the study of ancient floods as recorded by river and lake sediments, trees, caves, and historical documents — is absolutely essential to judge the real risk of large, rare floods. And I’ll use examples from North America to illustrate how a ‘deeper river memory’ can help people evaluate their own vulnerability to floods, weigh the potential benefits of proposed infrastructure projects, and become more aware of what nature is truly capable of producing.

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Expecting the unexpected: The relevance of old floods to modern hydrology

  1. 1. THE RELEVANCE OF OLD FLOODS TO MODERN HYDROLOGY Geographisches Institut | Johannes Gutenberg-Universität Mainz | May 18, 2017
  2. 2. HOW MUCH TIME IS NEEDED TO TRULY KNOW A RIVER?
  3. 3. THE RHINE IN MAINZ
  4. 4. Source: Fredrik Von Erichsen/AFP/Ge y Images
  5. 5. THE MISSISSIPPI IN MINNEAPOLIS
  6. 6. THE MISSISSIPPI DURING THE 1988 DROUGHT
  7. 7. WINNIPEG, CANADA
  8. 8. THE RED RIVER OF THE NORTH
  9. 9. THE RED RIVER OF THE NORTH
  10. 10. Source: Morningstarphoto
  11. 11. 0.5 METRES PER KILOMETER THE RHINE THE RED 0.08 METRES PER KILOMETER STREAM GRADIENT
  12. 12. LAKE AGASSIZ
  13. 13. 1950
  14. 14. DURING EXTREME CASES, THE FLOOD ZONE OF THE RED RIVER CAN EXTEND 40 KM WIDE.
  15. 15. “ ”BACK IN 1997, THE WATER SPILLED ONTO THE FLAT PRAIRIE LIKE AN OPEN BOTTLE OF CHOCOLATE MILK THAT HAD TIPPED OVER ON THE KITCHEN TABLE. Roy MacGregor The Globe and Mail, August 7, 2015
  16. 16. Source: Greg Brooks 1997
  17. 17. River diversion Main channel Source: Dr. Greg Brooks, Geological Survey of Canada IN THE 1960s, WINNIPEG BUILT A 47-KM LONG DIVERSION CHANNEL THAT DIVERTS RED RIVER AROUND THE CITY.
  18. 18. GRAND FORKS, NORTH DAKOTA
  19. 19. THE 1997 RED RIVER FLOOD (AND FIRE) CAUSED MORE THAN $3.5 BILLION IN DAMAGES.
  20. 20. WINNIPEG GRAND FORKS
  21. 21. RIVER MEMORY
  22. 22. FLOODS — BY THEIR NATURE — ARE RARE EVENTS.
  23. 23. EVALUATE VULNERABILITY JUDGE INFRASTRUCTURE BE MORE AWARE OF NATURE’S POTENTIAL A DEEP ‘RIVER MEMORY’ IS ESSENTIAL TO:
  24. 24. 2UNCOVERING ANCIENT FLOODS
  25. 25. 1GAUGING FLOOD RISKS
  26. 26. Source: Roland Schlager/EPA
  27. 27. Source: AON Benfield, 2016 Annual Global Climate and Catastrophe Report FLOODS HAVE BEEN THE COSTLIEST PERIL FOR THE PAST 4 CONSECUTIVE YEARS, AND CAUSED $62B IN LOSSES GLOBALLY IN 2016.
  28. 28. Source: Guha-Sapir et al, 2015, Annual Disaster Statistical Review 2015. OVER THE PAST DECADE FLOODS KILL NEARLY 7000 PEOPLE WORLDWIDE EACH YEAR.
  29. 29. “ ”NO ONE IS GOING TO MOVE ST. LOUIS JUST BECAUSE IT HAPPENS TO BE IN THE RIVER. David Johnston The Ohio State University
  30. 30. The Quad Cities River Bandits and the Peoria Chiefs play a baseball game April 20, 2011 inside Modern Woodmen Park in Davenport, Iowa.
  31. 31. SACRAMENTO RIVER, CALIFORNIA
  32. 32. WHAT ARE THE RISKS POSED BY FUTURE FLOODS?
  33. 33. FFA(Flood Frequency Analysis)
  34. 34. FFACITY PLANNING INSURANCE PRICING MANAGEMENT PLANS
  35. 35. NEAR TUCSON, ARIZONA
  36. 36. THE RILLITO RIVER, TUCSON
  37. 37. “ ”THE 100-YEAR FLOOD HAS COME AND GONE SO, BY ALL RIGHTS, TUSCONANS SHOULD ENJOY ANOTHER CENTURY OF GREAT SOUTHWEST WEATHER. Metropolitan Tucson Convention and Visitor’s Bureau Sent immediately a er a severe flood
  38. 38. FREQUENCY MAGNITUDEsmall large common rare
  39. 39. EMIL GUMBEL (MATHS)
  40. 40. “ ”FOR THE TWO OR THREE EXTREME FLOODS, THE RETURN PERIODS ARE BASED ON A FEW OBSERVATIONS, AND CONSEQUENTLY, THE AGREEMENT IS NOT VERY GOOD. Gumbel, 1941 The Annals of Mathematical Statistics
  41. 41. An aerial image of downtown shows flood-affected areas June 13, 2008 in Cedar Rapids, Iowa
  42. 42. EVEN WITH KNOWLEDGE OF A HISTORICAL FLOOD IN 1851, THE 2008 FLOOD IS STILL NEARLY TWICE AS LARGE AS ANY OTHER FLOOD ON RECORD. 0 1000 2000 3000 4000 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Discharge (m3/s)
  43. 43. PASSAU, GERMANY
  44. 44. Source: Christian Gries
  45. 45. “ ”FOR GREATER FLOODS, THE MAXIMUM KNOWN FLOOD ELEVATION IS MORE IMPORTANT THAN ITS RECURRENCE INTERVAL. IF THE FUTURE IS LIKE THE PAST, THE OLDEST AND SIMPLEST IDEA IS THE BEST - A FUTURE FLOOD COULD RISE AT LEAST AS HIGH AS THE PREVIOUS MAXIMUM. James Eychaner Lessons from a 500-year Record of Flood Elevations
  46. 46. 2UNCOVERING ANCIENT FLOODS
  47. 47. WHAT ARE THE RISKS POSED BY FUTURE FLOODS?
  48. 48. THE FIRST STREAM GAGE IN THE UNITED STATES WAS ESTABLISHED AT EMBUDO, NM IN 1889.
  49. 49. PALEOFLOOD HYDROLOGY
  50. 50. VIC BAKER, UNIVERSITY OF ARIZONA
  51. 51. “ ”PALEOFLOODS ARE PAST OR ANCIENT FLOODS THAT OCCURRED WITHOUT BEING RECORDED BY EITHER (1) DIRECT HYDROLOGICAL MEASUREMENT DURING THE COURSE OF OPERATION (KNOWN AS INSTRUMENTAL OR “SYSTEMATIC” RECORDING) OR (2) OBSERVATION AND/OR DOCUMENTATION BY NON-HYDROLOGISTS. Victor Baker (2008) Paleoflood hydrology: Origin, progress, prospects
  52. 52. COLORADO RIVER RED RIVER OF THE NORTH
  53. 53. Source: Katie Rampala
  54. 54. Source: Robert Jarre , US Geological Survey SLACKWATER DEPOSITS
  55. 55. Source: Greenbaum et al., (2014), Water Resources Research.
  56. 56. 44“100-YEAR FLOODS” IN THE PAST 2100 YRS.
  57. 57. “ ”OUR RESULTS INDICATE THAT VERY LARGE FLOODS (A) ARE MUCH MORE FREQUENT THAN INDICATED BY PREVIOUS ESTIMATIONS WHICH WERE BASED EXCLUSIVELY ON ANALYSIS OF THE MEASURED, SYSTEMATIC GAGE RECORD, AND (B) THEIR FREQUENCY HAS INCREASED DURING THE LAST 500 YEARS. Greenbaum et al, 2014 Water Resources Research
  58. 58. PMF(Probable Maximum Flood)
  59. 59. THE ESTIMATED DISCHARGES FOR THE TWO LARGEST PALEOFLOODS ARE BIGGER THAN THE PROBABLE MAXIMUM FLOOD FOR THE MOAB VALLEY.
  60. 60. “ ”WHAT SHOULD BE DONE IF A STIPULATED PMF VALUE (WHAT IS THEORIZED TO BE THE FLOOD THAT WILL RESULT FROM THE “MOST SEVERE COMBINATION OF CRITICAL METEOROLOGICAL AND HYDROLOGIC CONDITIONS THAT ARE REASONABLY POSSIBLE”) IS DISCOVERED TO BE CONTRARY TO WHAT ACTUALLY EXISTS IN NATURE? Greenbaum et al, 2014 Water Resources Research
  61. 61. Source: FlickrLiren Chen THE RED RIVER OF THE NORTH
  62. 62. WINNIPEG GRAND FORKS
  63. 63. GRAND FORKS 1872
  64. 64. WINNIPEG 1812
  65. 65. FORT GARRY, HUDSON’S BAY COMPANY
  66. 66. MAY 31826
  67. 67. THE RIVER ROSE SIX FEET LAST NIGHT PERPENDICULARLY , SEVERAL TENTS ARE NOW PITCHED UPON THE MOST ELEVATED SPOTS: TERROR IS STRONGLY DEPICTED ON EVERY COUNTENANCE. “ ” David Jones Journal May 1826
  68. 68. MAY 51826
  69. 69. THE RIVER OVERFLOWED ITS BANKS EVERY WHERE, AND CARRIED THE ICE WITH GREAT VELOCITY TO A GREATER DISTANCE FROM ITS COURSE, THAN HAD EVER BEEN SEEN BEFORE BY THE OLDEST INHABITANTS. “ ” Red River Journal May 1826
  70. 70. MAY 161826
  71. 71. THE WHOLE FACE OF THE COUNTRY, BOTH BELOW AND ABOVE OUR ENCAMPMENT IS COVERED WITH WATER, AND IN THIS WINDY WEATHER, LOOKS LIKE AN IMMENSE LAKE IN A STORM. “ ” Red River Journal May 1826
  72. 72. SIR SANFORD FLEMING
  73. 73. THE LARGEST FLOODS ARE KNOWN FROM HISTORICAL ACCOUNTS AND POST HOC SURVEYS OF LOCAL ELDERS. Source: Manitoba Conservation and Water Stewardship 0 60,000 120,000 180,000 240,000 2006 1996 1979 1950 2011 1861 2009 1997 1852 1826 discharge (cfs) historical reports river gauges
  74. 74. 1950
  75. 75. Source: Greg Brooks 1997
  76. 76. QUERCUS
  77. 77. √ 24 OAK TREE RINGS (NORMAL ANATOMY)
  78. 78. 91 Source: St. George and Nielsen, The Holocene, 2003 1826 19
  79. 79. 700-YRFLOOD
  80. 80. … ALTHOUGH THE 1826 FLOOD DEVASTATED THE FLEDGLING RED RIVER SETTLEMENT, IT ALSO LED TO THE DEVELOPMENT OF A SUPERIOR LEVEL 
 OF FLOOD PROTECTION FOR MODERN WINNIPEG… “ ” St. George and Rannie Canadian Water Resources Journal, 2003
  81. 81. HOW MUCH TIME IS NEEDED TO TRULY KNOW A RIVER?
  82. 82. Source: Fredrik Von Erichsen/AFP/Ge y Images
  83. 83. “ ”(RHENUS) FLUVIUS GALLIAE QUI GERMANOS A GALLIA DIVIDIT. (THE RHINE IS A) RIVER OF GAUL, WHICH DIVIDES THE GERMANIC PEOPLE FROM GAUL. Maurus Servius Honoratus Commentary on the Aeneid of Vergil 4th Century CE
  84. 84. EVALUATE VULNERABILITY JUDGE INFRASTRUCTURE BE MORE AWARE OF NATURE’S POTENTIAL A DEEP ‘RIVER MEMORY’ IS ESSENTIAL TO:
  85. 85. VIC BAKER, UNIVERSITY OF ARIZONA
  86. 86. THE HISTORY OF PAST FLOODS, NOT THE HISTORICAL IDEALIZATION OF THEIR FUTURE POSSIBILITIES, IS THE UNDERSTANDABLE BASIS UPON WHICH PEOPLE MAY BE GUIDED TO EFFECTIVE ACTION. “ ” Baker et al., 2002 The Scientific and Societal Value of Paleoflood Research
  87. 87. MANITOBA MUSEUM
  88. 88. 103 Source: St. George and Nielsen, The Holocene, 2003 1826 19
  89. 89. MANITOBA MUSEUM
  90. 90. “ ”Believe me, you will find more lessons in the woods than in books. Trees and stones will teach you what you cannot learn from masters. ST. BERNARD OF CLAIRVAUX 1090 - 1153 CE
  91. 91. @sco stgeorge

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