A 1300 year reconstruction of paleofloods using oxbow lake sediments in temperate southwestern Quebec, Canada

摘要

The study of paleofloods provides important information on past flood frequency and intensity for regions where there is a paucity of records; it therefore extends our knowledge of flood occurrence beyond the historical record. Many paleoflood reconstructions come from the arid dry climate of southwestern USA and from Europe, with few studies being conducted in temperate climates of North America. This study uses sediment cores from oxbow lakes to reconstruct past flood events in a temperate region. Cores extracted from two oxbow lakes along the Desert River in southwestern Quebec, Canada, were analyzed for magnetic susceptibility, loss on ignition, and grain size and were radiocarbon dated (C-14). Using a combination of magnetic susceptibility variations, along with changes in grain size and organic material content, five floods were identified within the 220 cm core (1300 years) from the North oxbow lake, and six floods in the 118 cm core (600 years) from the South oxbow lake. This study provides evidence to support the use of oxbow lakes in temperate regions as a proxy of past floods, thus helping us understand hydroclimatic changes at regional scales. Data that span a longer period of time and in different environments are key to increase flood modelling accuracy to improve mitigation strategies under a changing climate.