The maximum capacity of water infrastructures is designed based on historical series of hydrological extremes and the hypothesis that the climate is stationary. However, the scientific consensus points towards a man-made global warming, with gradual repercussions on extreme precipitation and streamflow. In addition, several recent works indicate that the natural climate variability has the potential to mask the effects of these anthropogenic climate changes, giving the illusion of climate stationarity. Therefore, the aim of this thesis is to improve the understanding of the impacts of this natural variability and climate change on hydrometeorological extremes.
In the first place, natural variability was explored through six major climate indices (e.g., El Niño) influencing climate in North America. Although these showed some potential in predicting the seasonal variability of mean temperatures and precipitation, they were much less promising in the prediction of hydrological extreme events variability. The combination of these six climate indices only resulted in a low predictive value of extreme precipitation and streamflow variability.
In a second place, the natural variability of mean and extreme precipitation was examined using large ensembles of climate simulations. This work led to a clearer picture of its influence on the detection of the climate change signal. At the local scale (e.g., a single weather station), natural variability will likely dominate the climate change signal from extreme precipitation until the end of the 21st century. However, at the regional scale (e.g., multiple weather stations), the detection of the climate change signal would be faster and more robust. Globally, natural variability has the potential to impede the detection of climate change on mean and extreme precipitation up to the middle or even the end of the century for many regions of the world.
Large ensembles of climate simulations have also been used to assess the impact of climate change on the probability of recurrence of hydrological extreme events. To begin, the projected changes for the 100-year rainfall with durations ranging from one hour to five days between the 1980-1999 and 2080-2099 periods were studied using two ensembles at the global scale and one at the regional scale covering northeastern North America and Europe. The results from these three ensembles suggest that extreme precipitation events, corresponding to the 100-year return period of the reference period, will become about four to five (two to four) times more frequent in average for the northeastern North America (Europe). In addition, the results suggest that, in general, a larger return period and/or a shorter duration will result in more important relative increases.
Next, projected changes in extreme floods were investigated more specifically for 3 567 large (> 500 km2) catchments in North America. The results suggest very distinct spatial patterns in terms of increases and decreases in the 100-year flood. The most significant changes were found to be reductions in flood generated from snowmelt in high latitude and/or high-altitude catchments and increases for catchments in the southeastern United States and the West
Coast, where rainfall is the leading cause of flooding.
Finally, climate change adaptation strategies were discussed following this work. These, together with the conclusions from this thesis, could further help engineers and decision makers to justify the implementation of adaptation measures to better protect the built environment and vulnerable populations.
| Date | 8 Apr 2019 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | François Brissette (Supervisor) & Alain Mailhot (Co-supervisor) |
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Martel, J.-L. (Author),
Brissette (Supervisor) & Mailhot (Co-supervisor),
8 Apr 2019Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering