The impact of climate change on seasonal floods of a southern Quebec River Basin

Abstract

AbstractGlobal warming predicted by general circulation models (GCM) is now a more and more generally agreed upon effect. The impact of climate change on summer and fall flooding on the Châteauguay River Basin (2500 km2), located at the southern end of the Quebec province (Canada), was investigated using results from the Canadian GCM (CGCM1) and a coupled hydrology–hydraulics model of the basin. Three 20‐year periods, corresponding to 1975–1995, 2020–2040 and 2080–2100, were used for the analysis. For each period, 24‐h precipitation depths corresponding to the 20 and 100‐year return periods were determined from a frequency analysis of the summer–fall maximum 24‐h precipitations using a general extreme value frequency distribution. 24‐h rainfall hyetographs were generated using region‐specific cumulative distributions provided by the Canadian Atmospheric Environment Service. These hyetographs were then used as inputs to the hydrology–hydraulics model to simulate hydrographs, maximum discharge and maximum water levels at two sections of the river. Results indicate potentially very serious increases in the volume of runoff, maximum discharge and water level with future climate change scenarios. The changes get more drastic as longer return periods are considered. Increases of up to 250% of the maximum water discharge are encountered and water levels are significantly higher than the current flood levels. If realistic, these scenarios indicate that important decisions will have to be taken to alleviate future increases in flooding damages in what is already a flood prone river. Copyright © 2001 John Wiley & Sons, Ltd.