The Flood of 2013: Investigating Seasonal Discharge, Turbidity, and Precipitation to Assess Changes in Channel Geomorphology and River Hydrology in The Elbow River, Alberta

Abstract

In the face of global environmental change, inconsistencies in the frequency and intensity of storm events are a predicted result of climate change. An unprecedented flood event in 2013 caused widespread geomorphic and hydrological change to the Elbow River, located in southwestern Alberta. The aim of this study was to characterize how the hydrology and geomorphology of the Elbow River from Highway 22 to Highway 8 (Twin Bridges) changed during and after the flood of 2013. A seven-year-long time series of 15-minute discharge and turbidity data as well as daily mean values of discharge, turbidity, and precipitation were analyzed monthly (August, September, October), seasonally, and annually (2011 – 2018). Data from these stations along the Elbow River were also examined through SSC-discharge hysteresis. Google satellite imagery from Google Earth Pro provided a visual analysis of geomorphic change throughout the study period. The results show the complex relationship between precipitation, discharge, and turbidity, due to the forces of fluvial geomorphology, landscape characteristics, and an extreme hydrological event, that have additional controls on suspended sediment mobilization. Satellite imagery revealed widespread geomorphic restructuring as a result of high rates of sediment deposition and erosion immediately after the flood. SSC-discharge hysteresis demonstrated that the 2013 flood mobilized mass amounts of suspended sediment into the channel through counter-clockwise hysteresis. The results show the Elbow River’s sensitivity to change but also the capacity to stabilize years after the event. An analysis of the hydrological regime of the Elbow River provides insights into the fluvial and geomorphological response to changes in sediment availability, and how these changes affect sediment transport following an extreme hydrological event. Results contribute to background knowledge that policy-makers can use to inform flood risk management.