This panel of presentations will feature the work of the graduate students associated with the LEADS program.
Severe flooding occurred in 1974, 1976, 2017 and 2019 in the Ottawa River Basin (ORB). The floods of 2017 and 2019 led to the evacuation of ~14,000 people and governmental costs of ~1 billion. The 2019 flood damage in the Ottawa River basin surpassed that of 2017 which was thought to be 100-year flood. Since then, there have been concerns about the repeated events of this kind. To avoid such expensive damage and better understand if these floods are due to anthropogenic climate change and/or land use changes, we need better spatial and long-term data on flood risks and vulnerabilities. Unfortunately, the regional flood records are short, and there are few stream flow gauges on unregulated basin tributaries. Therefore, there is not enough data to accurately estimate the natural 100-year flood return periods in the sub-basins. This missing long-term data on the frequency and magnitude of major flooding can be inferred using floodwater sediments that are different from sediments deposited in non-flood conditions. Past floods in ORB will be reconstructed and mapped by taking sediment cores from oxbow lakes of four tributaries of the ORB, radiometrically dating them, and analyzing their past changes in composition using X-ray fluorescence, magnetic susceptibility, particle size analysis and percent organic matter, etc. Also, we will examine how human landscape disturbance and/or global warming has affected floods during the last century, relative to the more natural nineteenth century floods.
Storms are pervasive dangers to coastal communities in Eastern Canada and, under future climate scenarios, these extreme weather events are projected to increase in frequency and intensity. However, the impacts of climate change on storm variability have not been studied extensively in this region, in part due to the short and incomplete instrumental storm record. Here we present a new, high-resolution record of storms over the late Holocene, based on the analysis of cores of 3.25 m and 7.00 m length from two ombrotrophic peatbogs on the Magdalen Islands, in the Gulf of St. Lawrence. The cores were dated by 14C and 210Pb, with the bottommost peat sediments dating to ~4920 BP and ~4720 BP, respectively. We applied principal component analyses (PCA) using 10 elements measured by XRF core scanning to understand sediment provenance. Our results indicate the presence of aeolian sediments from local beach sand and sandstone cliffs characterized by the presence of K, Ti, Si, and Zr. We used a combination of aeolian sand and titanium content to identify allochthonous sediments that were deposited during extreme weather events, and validated these using the instrumental hurricane record from the Magdalen Islands from the past 150 years. Our storm reconstruction indicates a particularly active period between 1400-1650 CE, when heightened activity was also identified in other studies from the northwestern North Atlantic, as well as a notable increase in storms since 1930 CE. While warm sea-surface temperature (SST) anomalies seem to have contributed to more frequent storms since 1930 CE, the 1400-1650 CE active period occurred during the Little Ice Age (LIA), a period of generally cooler SSTs in the North Atlantic. Our study is the first to use ombrotrophic peat cores to track storm frequency in eastern North America, as well as one of the northernmost on the continent, and highlights the ambiguous impacts of SSTs on mid-latitude storms. Future research should focus on understanding the climatic factors that control storm variation in Eastern Canada, especially over the last millennium.