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The effects of climate change on sediment yield and transport dynamics in cold climate regions are not well understood or reported. In this study, the Soil and Water Assessment Tool (SWAT) has been built-up, calibrated, and validated against streamflow and sediment load at several monitoring stations in a cold climate region watershed - the Athabasca River Basin (ARB) in Alberta, Canada. The model was then fed with bias-corrected spatial disaggregated high-resolution (~ 10 km) future climate data from three climate models for two emission scenarios (RCP 4.5 and 8.5), and two periods (mid- and end-century). Results show that channel erosion and deposition are the dominant processes over hill slope erosion in the basin. On average, a predicted warmer and wetter future climate has both synergetic and offsetting effects on sediment yield. Changes are sub-region specific and land-use type dependent, thus reflecting a marked spatial and temporal heterogeneity within the basin. Increases on sediment yield in future periods in the agricultural areas are up to 0.94 t/ha/yr, and are greater than reported soil formation rates in the region. Similarly, while substantial increases (by more than two fold) in the sediment load transport through the river reaches were obtained, the changes show both temporal and spatial variability, and are closely aligned with the trend of stream flows. We believe that availability of such models and knowledge of the effect of future climatic conditions would help water managers formulate appropriate scenarios to manage such basins in a holistic way. However, significant uncertainties in future sediment yield and transport, as a result of variations in climatic forcing of different climate models, need to be considered in any adaptation measures. [ABSTRACT FROM AUTHOR]

We use annually laminated lake sediments to estimate suspended sediment yield for a 3850 km2 montane catchment in the British Columbia Coast Mountains. Sediment yield over the past 369 years averages 213 ± 38 Mg·km−2·a−1. Sediment yield increases to 285 ± 50 Mg·km−2·a−1 during the first half of the twentieth century and declines thereafter. The frequency of high-yield events during the 369 year period is irregular: 11 of the 34 events occur in the early part of the twentieth century, a time when glaciers in the watershed underwent major retreat. We fitted a generalized extreme value (GEV) model to estimate quantiles of the sediment yield distribution, and we used epoch analysis to examine persistence in sediment yield following 34 of the largest events. Persistence is greatest for the most extreme events; it is more variable for events that recur, on average, every 10-25 years. Our results indicate that sediment yield is linked to long-term changes in sediment supply to the lake. The results of this study extend earlier sediment yield estimates and improve understanding of linkages to watershed geomorphology, recent glacier retreat, and landslides in the Lillooet River watershed. [ABSTRACT FROM AUTHOR]

Abstract: Runoff from agricultural watersheds can carry a number of agricultural pollutants and pathogens; often associated with the sediment fraction. Deposition of this sediment can impact water quality and the ecology of the river, and the re-suspension of such sediment can become sources of contamination for reaches downstream. In this paper a modelling framework to predict sediment and associated microbial erosion, transport and deposition is proposed for the South Nation River, Ontario, Canada. The modelling framework is based on empirical relationships (deposition and re-suspension fluxes), derived from laboratory experiments in a rotating circular flume using sediment collected from the river bed. The bed shear stress governing the deposition and re-suspension processes in the stream was predicted using a one dimensional mobile boundary flow model called MOBED. Counts of live bacteria associated with the suspended and bed sediments were used in conjunction with measured suspended sediment concentration at an upstream section to allow for the estimation of sediment associated microbial erosion, transport and deposition within the modelled river reach. Results suggest that the South Nation River is dominated by deposition periods with erosion only occurring at flows above approximately 250 m3 s−1 (above this threshold, all sediment (suspended and eroded) with associated bacteria are transported through the modelled reach). As microbes are often associated with sediments, and can survive for extended periods of time, the river bed is shown to be a possible source of pathogenic organisms for erosion and transport downstream during large storm events. It is clear that, shear levels, bacteria concentrations and suspended sediment are interrelated requiring that these parameters be studied together in order to understand aquatic microbial dynamics. It is important that any management strategies and operational assessments for the protection of human and aquatic health incorporate the sediment compartments (suspended and bed sediment) and the energy dynamics within the system in order to better predict the concentration of indicator organism. [Copyright &y& Elsevier]

An overview of cohesive sediment transport processes is given in this paper, and a mass-balance equation that is commonly used to treat cohesive sediment transport is reviewed. The equation highlights transport parameters and processes that are important for modelling the transport of cohesive sediment. The flocculation mechanism that distinguishes cohesive sediment from its noncohesive counterpart is elaborated using a laboratory study that was carried out in a rotating circular flume using sediments from Hay River, Northwest Territories, Canada. A mathematical model of flocculation suitable for predicting flocculation of sediment in rotating circular flumes is reviewed. Other cohesive sediment transport processes such as erosion and deposition processes at the sediment-water interface, entrapment of fines in gravel beds, consolidation, fluid mud, and fluidization due to wave action are reviewed. Additional challenges and knowledge gaps that exist in the area of cohesive sediment transport are identified. [ABSTRACT FROM AUTHOR]

In this article, we quantify the effects of a standing ice cover on the hydrodynamics of a mesotidal estuary. The Portneuf Estuary, Québec, is 5.9 km in length and has a 3-m-deep thalweg. According to our numerical model simulations (using an adapted version of Environment Canada’s ONE-D model) and field measurements, the midwinter 50-cm-thick ice cover produced an attenuation of the neap tidal range (1.9 m) and spring tidal range (4.0 m) of 17 and 37%, respectively, near the upstream end of the estuary. The arrival of low water was also delayed by about 90 min at this location. At the mouth, the cover attenuated peak ebb tide flow (200 m3/s) and flood tide flow (500 m3/s) by approximately 18 and 13%, respectively. Here the peak flood flow was normally delayed by 41 min, while the ebb tide was usually advanced by 8 min. In general, the ice cover attenuated peak velocities by 12 to 20%, although at certain times and locations the ice cover could induce higher velocities than would be present under open water conditions. The ice cover also retarded and diminished the salt wedge intrusion and is expected to dramatically reduce the sediment transport processes, although its presence could cause some sporadic local increases in erosion. [ABSTRACT FROM AUTHOR]

High-frequency measurements of airflow from ultrasonic anemometers and time-averaged cup anemometer profiles were taken during an oblique alongshore sand-transporting event (6.7 m/s) over a vegetated foredune in May 2002 as part of a larger study on the sedimentary dynamics of a beach-dune complex in Greenwich Dunes, Prince Edward Island National Park, Canada. Local flow and sand transport pathways deviated significantly from the regional wind because of topographic steering of oblique alongshore airflow on the beach back toward the foredune in the backshore. Flow decelerated on the lower seaward slope of the foredune because of flow stagnation and vegetation-induced roughness effects. On the upper seaward slope, flow veered crest-parallel because of secondary flow effects, including potential flow reversal, acceleration, and interaction with faster regional flow. An inflection point in velocity profiles indicates a momentum sink at plant canopy height, and above this height exists a distinct shear layer. Flow acceleration occurs only on the upper slope above the plant canopy as the shear layer intensifies. Flow steadiness, as indicated by the coefficient of variation in horizontal (U) and vertical (W) velocity, also declines up the seaward slope, in contrast to measurements of flow over unvegetated dunes, perhaps because of increasing vegetation-induced drag and turbulence. Gusting and vertical bursting was evident as honami motion in the beachgrass and was responsible for maintaining intermittent saltation into the foredune. Temporal correlations exist between U, W, and flow angle. As flow shifted onshore, both U and W increased because of enhanced topographic forcing and increased vertical lift on the lower seaward slope, whereas when flow shifted alongshore, U and W declined because of reduced forcing and acceleration effects because the dune is effectively less steep to flow. Although these dunes align well with the vector of the regional resultant sediment drift potential, sand transport pathways followed local flow vectors of varying magnitude and direction. Offshore to oblique alongshore winds are typical of the summer wind regime, and, although frequently incompetent, they contribute to dune maintenance by cycling sand to the backshore for incipient foredune growth, scarp infilling, or both. To date, the role of secondary flows under alongshore winds in foredune morphodynamics has not been well documented. [ABSTRACT FROM AUTHOR]