Étienne Boucher (LAVAL) Yves Bégin (INRS-ETE)  Dominique Arseneault (UQAR) River Ice Jams  Risk evaluation, driving condit...
Introduction River ice breakup:  a crucial moment in the annual cycle of high-latitude rivers  Mechanical breakups Thermal...
Introduction Ice jams:   the most threatening hazard in northern areas
Introduction <ul><li>In most cold-regions however, very little is known on :  </li></ul>-The  frequency  of ice jams (and ...
Introduction Planar view Profile view streamflow Year 1 Year 2 [email_address]
General objectives 1- Obtain, through dendrochronology, spatio-temporally extended records of river ice jams  <ul><li>2- U...
Study site: the Necopastic River (250km²) -Undisturbed -Homogeneous lithology -Constant density of forest stands  -Frequen...
Amont: 15 sites Mi-bassin: 16 sites Aval:  7 sites  = Ice scouring activity = No ice scouring activity Study site: the Nec...
= Ice scouring activity = No ice scouring activity Study site: the Necopastic River (250km²) Upper basin: 15 sites Mid-bas...
Methods At each site: 1) Quantifying  geometric properties  of river channel [email_address]
2)  Geomorphological survey  (form and processes) ( Geomorphological Survey Technique, Thorne (1998)) <ul><li>Chenal morph...
Methods At each site 3)  Dendrochronological sampling [email_address]
Methods (dendrochronological principles)  1) Site selection Select sites that are  rectilinear  and of  constant width, de...
2) Stem selection (sensitivity)  Sensitive  (large)  Insensitive (small)  snow Ice 1) Site selection Methods (dendrochrono...
Sensitive  Insensitive RFS  (Radius at the First Scar) 2) Stem selection (sensitivity)  1) Site selection Methods (dendroc...
<ul><li>Evaluate the quality of the sampling </li></ul><ul><li>- ISR Algorithm </li></ul><ul><li>Iterative Sampling with R...
<ul><li>Evaluate the quality of the sampling </li></ul><ul><li>- ISR Algorithm </li></ul><ul><li>Iterative Sampling with R...
> The  intensity  of a an ice-jam at year «  t  » ( I t ) is calculated from the proportion sites recording an event that ...
Hydro-climatic analysis of the tree-ring series [email_address] Nécopastic (250km²) LG-1 (1500km²)
Discharge (m³) Time Hydro-climatic analysis of the tree-ring series END  of hydrograph recession (d) DUR_REC Duration of r...
Hydro-climatic analysis of the tree-ring series [email_address] Time resoltution Variable Dimensions Period Spatial scale ...
-CART modelling Hydro-climatic analysis of the tree-ring series -80%  of all years (1950-2003, N=54) are well simulated wi...
Fresh snow and cold spring temperatures delay the thermal degradation of the ice Arctic Oscillation (positive phase) Hydro...
Intense ice-scouring No ice-scouring Early and « flash » floods Favor intense mechanical breakups  Hydro-climatic analysis...
Geomorphological impact Does it vary as a function of ice-jam frequency? [email_address] Frequency = 9 events / (2008-1975...
Reconstructed ice jam frequencies  Geomorphological impact [email_address]
Upper Mid Lower <ul><li>Important variability at mid-basin  -W   </li></ul><ul><li>- Aw </li></ul>Hydaulic geometry  Geomo...
Geomorphological impact Upper Mid Lower [email_address]
Ice scoured channels Geomorphological impact [email_address] Genetic floodplain Erosion talus Ice scouring terrace Scarred...
Conceptual model relating ice-jam frequencies and riverbank adjustment Geomorphological impact [email_address] F  ≥  0.2 F...
Conclusions & perspectives <ul><li>A  spatio-temporal perspective  is crucial to a deeper understanding of river-ice break...
Funding … [email_address]
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River ice jams : risk evaluation, driving conditions and geomorphological impacts documented from tree-rings, Necopastic River Canada

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This ppt describes my scientific activities over the last few years. It is of interest for scientists and engineers how want to know more about long-term ice jams dynamics and physical impacts. Please contact me for more info:
boucher@cerege.fr

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River ice jams : risk evaluation, driving conditions and geomorphological impacts documented from tree-rings, Necopastic River Canada

  1. 1. Étienne Boucher (LAVAL) Yves Bégin (INRS-ETE) Dominique Arseneault (UQAR) River Ice Jams Risk evaluation, driving conditions and geomorphological impacts documented from tree-rings Necopastic River, James Bay Contact: [email_address]
  2. 2. Introduction River ice breakup: a crucial moment in the annual cycle of high-latitude rivers Mechanical breakups Thermal breakups [email_address]
  3. 3. Introduction Ice jams: the most threatening hazard in northern areas
  4. 4. Introduction <ul><li>In most cold-regions however, very little is known on : </li></ul>-The frequency of ice jams (and their spatio-temporal variations) -The hydro-climatic conditions (or thresholds) that trigger these extremes -The geomorphological impacts of ice regimes Main reason: - Hydrological records are too short and only provide site specifc information on a spatially variable phenomenon
  5. 5. Introduction Planar view Profile view streamflow Year 1 Year 2 [email_address]
  6. 6. General objectives 1- Obtain, through dendrochronology, spatio-temporally extended records of river ice jams <ul><li>2- Use these data to document: </li></ul><ul><li>Hydro-climatic context </li></ul><ul><li>B) Geomorphological impacts </li></ul>[email_address]
  7. 7. Study site: the Necopastic River (250km²) -Undisturbed -Homogeneous lithology -Constant density of forest stands -Frequent ice-scouring events / but not destructive -Climatically homogeneous Many advantages -Winter breakup = rare [email_address]
  8. 8. Amont: 15 sites Mi-bassin: 16 sites Aval: 7 sites = Ice scouring activity = No ice scouring activity Study site: the Necopastic River (250km²) [email_address]
  9. 9. = Ice scouring activity = No ice scouring activity Study site: the Necopastic River (250km²) Upper basin: 15 sites Mid-basin: 16 sites Lower-basin: 7 sites [email_address]
  10. 10. Methods At each site: 1) Quantifying geometric properties of river channel [email_address]
  11. 11. 2) Geomorphological survey (form and processes) ( Geomorphological Survey Technique, Thorne (1998)) <ul><li>Chenal morphology </li></ul><ul><li>Riverbank morphology </li></ul><ul><li>-Floodplain caracterisation </li></ul><ul><li>-Channel to valley description </li></ul>At each site: Methods [email_address]
  12. 12. Methods At each site 3) Dendrochronological sampling [email_address]
  13. 13. Methods (dendrochronological principles) 1) Site selection Select sites that are rectilinear and of constant width, depth & slope [email_address]
  14. 14. 2) Stem selection (sensitivity) Sensitive (large) Insensitive (small) snow Ice 1) Site selection Methods (dendrochronological principles) [email_address]
  15. 15. Sensitive Insensitive RFS (Radius at the First Scar) 2) Stem selection (sensitivity) 1) Site selection Methods (dendrochronological principles) [email_address]
  16. 16. <ul><li>Evaluate the quality of the sampling </li></ul><ul><li>- ISR Algorithm </li></ul><ul><li>Iterative Sampling with Replacement </li></ul>3) Replication 2) Stem selection (sensitivity) 1) Site selection Methods (dendrochronological principles) [email_address]
  17. 17. <ul><li>Evaluate the quality of the sampling </li></ul><ul><li>- ISR Algorithm </li></ul><ul><li>Iterative Sampling with Replacement </li></ul><ul><li>b) Exacerbate the regional signal </li></ul>3) Replication 2) Stem selection (sensitivity) 1) Site selection Methods (dendrochronological principles) [email_address]
  18. 18. > The intensity of a an ice-jam at year «  t  » ( I t ) is calculated from the proportion sites recording an event that year Methods (dendrochronological principles) [email_address]
  19. 19. Hydro-climatic analysis of the tree-ring series [email_address] Nécopastic (250km²) LG-1 (1500km²)
  20. 20. Discharge (m³) Time Hydro-climatic analysis of the tree-ring series END of hydrograph recession (d) DUR_REC Duration of recession (t) DUR_RISE Duration of rise (t) PEAK Peak discharge (m³ s -1 ) DTE_PEAK Date of flood peak (d) START of hydrograph rise (d) VOL Flood volume (m³) VOL_RISE Volume during rising limb (m³)
  21. 21. Hydro-climatic analysis of the tree-ring series [email_address] Time resoltution Variable Dimensions Period Spatial scale TEMPERATURES Source: IREQ, HQ / D. Tabsoba Monthly T_min, T_max, T_mean °C 1960-2003 LG-1 PRECIPITATION Source: IREQ, HQ/ D. Tabsoba Montlhy Total precipitation (PREC) cm / day 1960-2003 LG-1 SNOW COVER Source: IREQ, HQ / D. Tabsoba Monthly Height (H) cm 1950-2003 LG-1 Monthly Water equivalent (SWE) cm 1950-2003 LG-1 Monthly Density (DENS) Kg / m³ 1950-2003 ARCTIC OSCILLATION Source: NOAA (bi) Montlhy (March-April) Index (AO) - 1950-2003 Northern Hemisphere
  22. 22. -CART modelling Hydro-climatic analysis of the tree-ring series -80% of all years (1950-2003, N=54) are well simulated with three variables [email_address]
  23. 23. Fresh snow and cold spring temperatures delay the thermal degradation of the ice Arctic Oscillation (positive phase) Hydro-climatic analysis of the tree-ring series [email_address] + -
  24. 24. Intense ice-scouring No ice-scouring Early and « flash » floods Favor intense mechanical breakups Hydro-climatic analysis of the tree-ring series [email_address]
  25. 25. Geomorphological impact Does it vary as a function of ice-jam frequency? [email_address] Frequency = 9 events / (2008-1975) = 0,27 year -1 ~ One event each three year 2008 1978 1982 1988 1991 1995 2000 2003 2007 2008 1975 Site X
  26. 26. Reconstructed ice jam frequencies Geomorphological impact [email_address]
  27. 27. Upper Mid Lower <ul><li>Important variability at mid-basin -W </li></ul><ul><li>- Aw </li></ul>Hydaulic geometry Geomorphological impact [email_address]
  28. 28. Geomorphological impact Upper Mid Lower [email_address]
  29. 29. Ice scoured channels Geomorphological impact [email_address] Genetic floodplain Erosion talus Ice scouring terrace Scarred trees with recent alluviums
  30. 30. Conceptual model relating ice-jam frequencies and riverbank adjustment Geomorphological impact [email_address] F ≥ 0.2 F < 0.2
  31. 31. Conclusions & perspectives <ul><li>A spatio-temporal perspective is crucial to a deeper understanding of river-ice breakup & jam dynamics + their geomorphological impacts </li></ul><ul><ul><li>Dendrochronology can bring this perspective </li></ul></ul>[email_address] -What about the future ?
  32. 32. Funding … [email_address]

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