On the Impact of Recent Climate Change on Seasonal Floods—A Case Study from a River Basin in Southern Quebec

Abstract

A study of the trends of climatic and hydrologic variables between 1960 and 2004 was completed for the Massawippi River basin in southern Quebec. Analysis of these trends was used to evaluate possible changes in the spring flood hazard in the basin. This basin is flood-prone, especially during the spring months, portions of the basin having been inundated 95 times during the 20th century. Trends were initially analyzed using plots of cumulative percentage departure from the mean, taken from the raw data. Statistical analyses of the data trends were conducted using the Mann-Kendall non-parametric test. The graphical and statistical results indicate trends toward increasing winter and spring temperatures and a change in precipitation type from snow to rain. Decreases in winter snow accumulations are particularly evident. Graphical analyses show some trend toward decreasing maximum and total river discharges, but the trends are not statistically significant. There is no clear evidence that changes in the climatic variables are causing significant changes in river or flood behaviour. Thus, there is no evidence that changing climatic conditions are creating a greater threat from flooding.