Floodplain sedimentation rates, soil properties and recent flood history in southern Québec

A Comparison of the Composition and Diversity of Tree Populations along a Hydrological Gradient in Floodplains (Southern Québec, Canada)

“…The years 1982, 1990 and 1996, which are characterized by peak discharge, are thus easily located on the mean annual discharge graph. The decrease in discharge recorded around 1960 and 1964 is also clearly identified [36,49]. Furthermore, the years marked by high discharge are generally years with considerable rainfall.…”

“…Sources: [38,39,[42][43][44][45][46] and compilation by the authors. The mean annual discharge of the section of the Saint-François River (the longest time series) located in the study area shows variations over the last decades , with a significant increase in river flow discharge, especially after the 1970s, preceded by a decrease in flow before 1960 [36,49]. The years 1982, 1994 and 1996 have the highest discharge and there is a significant increase in the mean annual discharge in the last few decades, especially from 1970-1998, with a downward trend after 2000 (Figure 2).…”

“…The soils in the alluvial plains consist mainly of Regosol, Gleyed Regosol and Brunisolic soils [35,36,40], with a mineral matrix mainly characterized by fine sediments (silt and fine sand) and drainage classified poor to moderately good [40]. Outside of the floodplains, the soil types are mostly Brunisolic and young Podzolic, consisting of a matrix mainly characterized by sand (fine or medium sand) that may contain gravel and a few blocks, with generally good or excessive drainage in sloped areas ( Table 2).…”

“…Frequent flooding can also disrupt pedogenetic processes and biogeochemical cycles and could alter the development of riparian vegetation [35][36][37]. For instance, organic matter (e.g., leaves, twigs, dead plants) can accumulate in the soil during the growing and fall seasons, but could be transported further downstream during flooding, thus causing soil degradation and depriving the vegetation of essential nutrients (e.g., carbon, nitrogen, phosphorus).…”

“…For instance, organic matter (e.g., leaves, twigs, dead plants) can accumulate in the soil during the growing and fall seasons, but could be transported further downstream during flooding, thus causing soil degradation and depriving the vegetation of essential nutrients (e.g., carbon, nitrogen, phosphorus). Studies conducted in southern Québec watersheds show that successive flooding results in soil depletion, which could adversely affect riparian ecosystems [35][36][37], particularly with respect to the regeneration of trees in the riparian areas. Increased recurrence of flooding may also result in floodplain vertical aggradation and a loss of nutrients.…”