Climate-Driven Trends in the Occurrence of Major Floods in North America and Europe

Glenn A Hodgkins, U.S. Geological Survey, New England Water Science Center, Augusta, United States, Paul H Whitfield, Environment Canada, Vancouver, BC, Canada, Donald H Burn, University of Waterloo, Civil and Environmental Engineering, Waterloo, ON, Canada, Jamie Hannaford, UK Centre for Ecology & Hydrology, Wallingford, United Kingdom, Benjamin Renard, INRAE, RECOVER, Aix Marseille University, Aix-En-Provence, France, Kerstin Stahl, Albert Ludwig University of Freiburg, Freiberg, Germany, Anne K Fleig, Norwegian Water Resources and Energy Directorate (NVE), Oslo, Norway, Henrik Madsen, DHI, Horsholm, Denmark, Luis Mediero, Universidad Politécnica de Madrid, Hydraulics, Energy and Environment, Madrid, Spain, Johanna Korhonen, Finnish Environment Institute, Helsinki, Finland, Conor Murphy, National University of Ireland, Maynooth, Co. Kildare, Ireland, Philippe Crochet, Icelandic Meteorological Office, Reykjavik, Iceland and Donna Wilson, Norwegian Water Resources and Energy Directorate, Oslo, Norway

Contact First Author: Glenn A Hodgkins; gahodgki@usgs.gov

Previously Published Material: Status and partial results from this project have been presented on posters at past AGU and EGU meetings. The project team is currently working on revisions based on journal review. We will resubmit to that journal after updates are complete. Resubmission will likely take place prior to the May Joint Assembly.

Abstract ID#: 33940

 

English Abstract:
We present an intercontinental assessment of historical climate-driven trends in major-flood occurrence—floods exceeding 25, 50, and 100 year return-period thresholds—using many diverse but minimally altered catchments. It is important to understand historical changes in major floods to help inform how floods may change in the future. To date there is very limited evidence of past changes in major-flood magnitude and occurrence. Many studies have analyzed annual-maximum flood trends (which primarily represent minor floods) and they have often not differentiated between trends influenced by human catchment alterations and those caused by climatic changes. Based on our results, there is no compelling evidence for consistent changes over time in major-flood occurrence across North America and Europe. Flood occurrence based on all 1206 gauges in our study increased from 1961 to 2010 but not significantly (p<0.05), driven primarily by European increases; there was no change overall in the occurrence of major floods in North America. Flood occurrence based on all 322 longer-record gauges increased from 1931 to 2010 but not significantly, this time driven primarily by North American increases. There were a few significant flood-occurrence increases and decreases for subgroups of gauges for both time periods, differentiated by catchment size, type of climate, flood threshold, and period of record. Significant increases from 1931-2010 in the occurrence of 25-year floods in North America appear to be driven by a relatively low occurrence of floods in the 1930s and 1940s. Past changes in major-flood occurrence are complex and future changes are also expected to be complex. International hydrologic networks containing minimally altered catchments will play an important role in understanding these complexities for both historical and future climatic conditions.
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