Évolution du risque hydrologique sur la rivière Châteauguay

Abstract

The 1990s have been marked by several hydro-meteorological extremes, to such an extent that it can be inquired if the riverside residents are exposed to a risk, which is increasing with time. This perception of an increasing risk could be due to a change in the frequency or intensity of the events, to a change in the exploitation of resources, or even to the media coverage of catastrophes. This article aims to study the progressive modification of the likelihood of flood event occurrence (maximum flow) in the Châteauguay River basin, based on available hydrometric data. The data has been studied, using homogeneity and statistical control tests, to examine the possibility of merging the data of two stations, in order to obtain a series, which is sufficiently long to reveal the evolution of hydrological risk and to study the change in the estimation of the 100-year return flood. The merged series was then divided into subsets on which frequency analyses were performed using the linear moments method. Estimations of the 100-year return flood from different samples did not present significant differences. The bootstrap technique was then used in order to quantify the uncertainty due to sampling. The results of the analysis show the absence of a general upward or downward trend of the hydrological risk on the Châteauguay River.Key words: hydrological risk, Châteauguay River, linear moments, bootstrap, statistical hydrology.[Journal translation]