Modelling the effects of climatic and hydrological regime changes on the sediment dynamics of the Fraser River Basin, British Columbia, Canada

Abstract

Future sediment dynamics may be affected by changing climates or hydrological regimes because of the close link between hydrology and sediment erosion, deposition, and transport. Previously, investigations of these potential changes have been constrained by a combination of limited observational data, hydrological drivers, and appropriate mechanistic models. Additionally, there is often ambiguity regarding how to disentangle the impacts of climate and hydrology from direct human factors such as reservoirs and land‐use change, which often exert more control over sediment dynamics. In this study, we utilize a recently developed, large‐scale, distributed, mechanistic sediment transport model to project future sediment erosion, deposition, and transportation within the Fraser River Basin in British Columbia, Canada—a basin with historical water flux and sediment load observations and limited anthropogenic influences upstream of its delta. The sediment model is driven by synthetic land‐surface hydrology derived from Scenarios A1B, A2, and B1 of the Special Report on Emissions Scenarios, which were provided by the Pacific Climate Impacts Consortium. Resulting simulations of water flux and sediment load from 1965 to 1994 are first validated against observational data then compared with future projections. Future projections show an overall increase in annual hillslope erosion and in‐channel transportation, a shift towards earlier spring peak erosion and transportation, and longer persistence of the sediment signal through the year. These shifts in timing and annual yield may have deleterious effects on spawning sockeye salmon and are insufficient to counteract future coastal retreat caused by sea‐level rise.

Climate Change Impacts on Sediment Yield and Debris‐Flow Activity in an Alpine Catchment

“…There have also been investigations of the impacts of climate variability on catchments and smaller hillslope scales (e.g. Mullan et al, 2012;Francipane et al, 2015;Shrestha & Wang, 2018;Tsuruta et al, 2019;Peleg, Skinner, et al, 2020;Battista et al, 2020), and on the sensitivity of sediment yield to land use and land cover change (e.g. Molnar et al, 2006;Coulthard & Van De Wiel, 2017;Yetemen et al, 2019).…”

“…Modeling experiments examining the sensitivity of basin sediment yield to climate change cover a large range of process scales and environments, particularly in relation to landscape evolution (e.g., Coulthard et al., 2012; Istanbulluoglu, 2009; Perron, 2017; Tucker & Slingerland, 1997). There have also been investigations of the impacts of climate variability on catchments and smaller hillslope scales (e.g., Battista et al., 2020; Francipane et al., 2015; Mullan et al., 2012; Peleg et al., 2020b; Shrestha & Wang, 2018; Tsuruta et al., 2019), and on the sensitivity of sediment yield to land use and land cover change (e.g., Coulthard & Van De Wiel, 2017; Molnar et al., 2006; Yetemen et al., 2019). The commonality of these studies is that the simulated variability in sediment yield is often very large.…”