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Hydrogeomorphology studies river dynamics, focusing on the interactions between flow structure, sediment transport, and the morphologies that characterize rivers and their watersheds. It provides an analytical framework and tools for better integrating knowledge of river dynamics into river management in the broadest sense, and more specifically, into river restoration as well as into the assessment and prevention of risks associated with fluvial hazards. In Quebec, hydrogeomorphology is emerging as a significant contribution to risk assessment and management approaches, and is at the heart of a paradigm shift in river management whereby process restoration aims to increase the resilience of fluvial systems and societies, and improve the quality of fluvial environments. This contribution outlines the trajectory of hydrogeomorphology in Quebec, based on scientific publications by Quebec geographers, and discusses the discipline's aims in research and knowledge integration for river management. Messages clés: Les géographes du Québec ont contribué fortement au développement des connaissances et outils de l'hydrogéomorphologie.L'hydrogéomorphologie a évolué d'une science fondamentale à une science où les connaissances fondamentales sont au service de la gestion des cours d'eau.L'hydrogéomorphologie et le cortège de connaissances et d'outils qu'elle promeut font de cette discipline une partenaire clé pour une gestion holistique des cours d'eau. [ABSTRACT FROM AUTHOR]

The c. 1.5–1.3 Ga Wilton package, the upper succession of the greater McArthur Basin, preserves detailed tectono-sedimentary evidence for the Mesoproterozoic evolution of the North Australian Craton (NAC). In addition, it is a valuable global sedimentary repository for the poorly explored Mesoproterozoic. New detrital zircon U–Pb age and Lu–Hf isotope data, collected from multiple, geographically separated, basins that make up the Wilton package, are compiled with previously published data to illuminate the basin evolution. The spatial and temporal variation in sedimentary provenance illustrates two major geographic changes that correspond to continent-scale tectonic convulsions of the NAC during the Mesoproterozoic. The first is shown by the influx of sediment sourced from east and southeast terranes. This is linked to rifting between Proterozoic Australia and Laurentia at c. 1.45 Ga, resulting in the uplift of the eastern margin of the NAC–SAC (South Australian Craton). The second basin geographic change is illustrated by a flux of southerly-sourced detritus that is interpreted to be tectonically driven by the uplift of the southern NAC, during the subduction/closure of the Mirning Ocean at c. 1.32 Ga. Spatially, sediment in the Wilton package is separated into two depositional systems: sedimentary rocks within the Birrindudu Basin, the western component of the Wilton package, have different detrital signatures relative to other Wilton package successions found east of the Daly Waters Fault Zone, in the Beetaloo Sub-basin, the McArthur Basin and the South Nicholson Basin. The Daly Waters Fault Zone is interpreted as an ancient bathymetric high, blocking sediment transport. Although they differ in sources, rocks in both the Birrindudu Basin and the eastern Wilton package record coeval shifts of basin provenance to southern sources. The coherent evolution of basin provenance indicates a consistent tectono-sedimentation history, and links the Birrindudu Basin and the other Wilton successions in a tectonic framework. [ABSTRACT FROM AUTHOR]

The Eastern Mediterranean Sea is a sink for terrigenous sediments from North Africa, Europe and Asia Minor. Its sediments therefore provide valuable information on the climate dynamics in the source areas and the associated transport processes. We present a high-resolution dataset of sediment core M40/4_SL71, which was collected SW of Crete and spans the last ca. 180 kyr. We analysed the clay mineral composition, the grain size distribution within the silt fraction, and the abundance of major and trace elements. We tested the potential of end-member modelling on these sedimentological datasets as a tool for reconstructing the climate variability in the source regions and the associated detrital input. For each dataset, we modelled three end members. All end members were assigned to a specific provenance and sedimentary process. In total, three end members were related to the Saharan dust input, and five were related to the fluvial sediment input. One end member was strongly associated with the sapropel layers. The Saharan dust end members of the grain size and clay mineral datasets generally suggest enhanced dust export into the Eastern Mediterranean Sea during the dry phases with short-term increases during Heinrich events. During the African Humid Periods, dust export was reduced but may not have completely ceased. The loading patterns of two fluvial end members show a strong relationship with the Northern Hemisphere insolation, and all fluvial end members document enhanced input during the African Humid Periods. The sapropel end member most likely reflects the fixation of redox-sensitive elements within the anoxic sapropel layers. Our results exemplify that end-member modelling is a valuable tool for interpreting extensive and multidisciplinary datasets. [ABSTRACT FROM AUTHOR]

Abstract: Cross-shore migratory behavior of nearshore sandbars is commonly studied with nearshore bathymetric-evolution models that represent underlying processes of hydrodynamics and sediment transport. These models, however, struggle to reproduce natural cross-shore sandbar behavior on timescales of a few days to weeks and have uncertain skill on longer scales of months to years. One particular concern for the use of models on prediction timescales that far exceed the timescale of the modeled processes is the exponential accumulation of errors in the nonlinear model equations. The relation between cross-shore sandbar migration, sandbar location and wave height has previously been demonstrated to be weakly nonlinear on timescales of several days, but it is unknown how this nonlinearity affects the predictability of long-term (months to years) cross-shore sandbar behavior. Here we study the role of nonlinearity in the predictability of sandbar behavior on timescales of a few days to several months with data-driven neural network models. Our analyses are based on over 5600 daily-observed cross-shore sandbar locations and daily-averaged wave forcings from the Gold Coast, Australia, and Hasaki, Japan. We find that neural network models are able to hindcast many aspects of cross-shore sandbar behavior, such as rapid offshore migration during storms, slower onshore return during quiet periods, seasonal cycles and annual to interannual offshore-directed trends. Although the relation between sandbar migration, sandbar location and wave height is nonlinear, sandbar behavior can be hindcasted accurately over the entire lifespan of the sandbars at the Gold Coast. Contrastingly, it is difficult to hindcast the long-term offshore-directed trends in sandbar behavior at Hasaki because of exponential accumulation of errors over time. Our results further reveal that during periods with low-wave conditions it becomes increasingly difficult to predict sandbar locations, while during high waves predictions become increasingly accurate. [Copyright &y& Elsevier]

Abstract: This study examines the erosive resistance of the discontinuous, loose joint blocks of various sizes that comprise the bed material of the Etobicoke Creek, an incised bedrock channel found in an urbanized setting within the city of Toronto, Ontario, Canada. In order to accomplish this, both field and laboratory experiments were conducted on the bed material found in this channel. The field work involved repeated detailed surveying of the channel bed and estimations of distances of movement of various clasts during many sediment transport events. We found that rates of erosion and/or deposition can be significant during the snowmelt spring events and that there was a greater loss of bed material over the study reach than was gained in several spots, with bed lowering >0.10m in some locations. The field work also showed that the distances moved by the rock clasts scaled directly with shear stresses observed during rain events and that average distances of transport tend to be short. The frequency distributions of distance of transport scaled with particle size is log-normally distributed. Flume experiments demonstrated that the clasts offered different levels of resistance to movement, depending on their orientation. The platy nature of the rock fragments, clast orientation, and their imbrication significantly affect the threshold of erosion. The results have significant implications for the understanding of bedrock rivers from a management perspective, especially in the case of those rivers experiencing the effects of urban development in their drainage basins. [Copyright &y& Elsevier]

Sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences (basin area and relief), geography (temperature, runoff), geology (lithology, ice cover), and human activities (reservoir trapping, soil erosion). A new model, termed "BQART" in recognition of those factors, accounts for these varied influences. When applied to a database of 488 rivers, the BQART model showed no ensemble over- or underprediction, had a bias of just 3% across six orders of magnitude in observational values, and accounted for 96% of the between-river variation in the long-term (±30 years) sediment load or yield of these rivers. The geographical range of the 488 rivers covers 63% of the global land surface and is highly representative of global geology, climate, and socioeconomic conditions. Based strictly on geological parameters (basin area, relief, lithology, ice erosion), 65% of the between-river sediment load is explained. Climatic factors (precipitation and temperature) account for an additional 14% of the variability in global patterns in load. Anthropogenic factors account for an additional 16% of the between-river loads, although with ever more dams being constructed or decommissioned and socioeconomic conditions and infrastructure in flux, this contribution is temporally variable. The glacial factor currently contributes only 1% of the signal represented by our globally distributed database, but it would be much more important during and just after major glaciations. The BQART model makes possible the quantification of the influencing factors (e.g., climate, basin area, ice cover) within individual basins, to better interpret the terrestrial signal in marine sedimentary records. The BQART model predicts the long-term flux of sediment delivered by rivers; it does not predict the episodicity (e.g., typhoons, earthquakes) of this delivery. [ABSTRACT FROM AUTHOR]

Glaciohydraulic supercooling is a process that allows water at the base of a glacier to remain liquid at a temperature below its freezing point in response to the geometry of water flow and subglacial pressure. Supercooling, and subsequent freezing, of subglacial water has implications for glacier dynamics, sediment transfer and landform evolution, and an understanding of the process is important both for understanding modern glacial environments and for reconstructing glacial environments of the past. However, recent research on glaciohydraulic supercooling has raised controversy both about the significance of the process and about the way in which it has been applied within the discipline. In this paper, we review recent work on supercooling in glaciers, assess its significance to glaciology, geomorphology and Quaternary science, and identify key issues requiring further research in order to resolve some of the controversy surrounding the topic. We suggest that, while glaciohydraulic supercooling is a very significant process, its adoption as an explanation of some phenomena has been premature, and that further research is required to test its true significance both in modern settings and in the glacial geologic record. [ABSTRACT FROM AUTHOR]

Grain-bed collision is a key component of saltation, but substantial uncertainty remains regarding many aspects of this process. Previous empirical work is used to develop a conceptual model of this process that accounts for the partitioning of impact energy between rebounding grains and the bed. The model envisions two distinct collision regimes: (i) a quasi-elastic regime at low impact speeds and (ii) an inelastic regime at high impact speeds. In the quasi-elastic regime, colliding grains retain a constant proportion of their kinetic energy, and thus rebound at speeds that are proportional to the impact speed and shear velocity. In the inelastic regime, colliding grains retain a fixed and limited amount of kinetic energy, transferring any excess above this limit to the bed. Rebound speeds are thus constant and independent of both impact speed and shear velocity. Impact energy transferred to the bed is expended in ‘deformation’ (i.e., ejection, rearrangement, etc. of bed grains). These two collision regimes are separated by a critical impact speed/kinetic energy level that is controlled by bed texture (more directly, by the inertia or resistance to motion of the bed grains). Field measurements under near-threshold conditions are found to correspond to the higher speed inelastic regime, suggesting that inelastic collisions predominate in aeolian saltation on loose, unconsolidated sand beds. The quasi-elastic regime might therefore only be pertinent for reptating grains, or in situations in which interparticle bonding (from crusts, surface moisture, etc.) increases the ‘effective’ inertia of bed grains and thus the critical impact speed separating the two regimes. It is also shown that rebound speed in the inelastic regime varies in inverse proportion to grain size (mass), so that particles rebound with an approximately constant level of kinetic energy regardless of size. Thus, larger grains will rebound at smaller speeds and follow lower, shorter trajectories, providing a mechanism that accounts for the commonly observed size sorting of grains subjected to aeolian saltation. [ABSTRACT FROM AUTHOR]

Field, documentary, and laboratory analyses show that geomorphic processes are a central component in explaining the origins and transportation of the 2,200 kg of mercury annually deposited in Lake Powell in Arizona and Utah. Almost all the mercury in the lake is derived from weathering of natural source rocks in the lake's 279,000 km2 drainage area and delivered in fluvial sediments. Of the mean annual mercury input to the lake, 40 percent comes from a single tributary, the Green River. The Colorado River contributes 40 percent of the water to the lake, but only 6 percent of the mercury. Local Canyon Lands streams contribute only 9 percent of the lake's water but 36 percent of the mercury and 40 percent of the sediment. Downstream distribution of mercury in fluvial sediments of ephemeral streams is directly related to exposures of geologic units in the contributing drainage area. In the arid and semi-arid Colorado Plateau, mercury is not generally associated with fine panicles, enrichment does not occur in the transition from host rock to stream sediments, and organic materials are largely absent from stream sediments and so do not play a significant role in concentrating mercury. The regional mercury budget shows a definite spatial structure: streams contributing large amounts of mercury to the lake either discharge large quantities of sediment or have extensive out-crops of particular geologic formations (Chinle or Morrison) in their drainage areas. Mercury in the Colorado Plateau streams demonstrates that understanding of chemical cycles in the natural environment depends in part on an appreciation of the spatial characteristics of the physical processes involved. [ABSTRACT FROM AUTHOR]