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This paper presents a modelling study on the spatial and temporal variability of climate-induced hydrologic changes in the Fraser River basin, British Columbia, Canada. This large basin presents a unique modelling case due to its physiographic heterogeneity and the potentially large implications of changes to its hydrologic regime. The macro-scale Variable Infiltration Capacity (VIC) hydrologic model was employed to simulate 30-year baseline (1970s) and future (2050s) hydrologic regimes based on climate forcings derived from eight global climate models (GCMs) runs under three emissions scenarios (B1, A1B and A2). Bias Corrected Spatial Disaggregation was used to statistically downscale GCM outputs to the resolution of the VIC model (1/16°). The modelled future scenarios for the 11 sub-basins and three regions (eastern mountains, central plateau and coastal mountains) of the FRB exhibit spatially varied responses, such as, shifts from snow-dominant to hybrid regime in the eastern and coastal mountains and hybrid to rain-dominant regime in the central plateau region. The analysis of temporal changes illustrated considerable uncertainties in the projections obtained from an ensemble of GCMs and emission scenarios. However, direction of changes obtained from the GCM ensembles and emissions scenarios are consistent amongst one another. The most significant temporal changes could include earlier onsets of snowmelt-driven peak discharge, increased winter and spring runoff and decreased summer runoff. The projected winter runoff increases and summer decreases are more pronounced in the central plateau region. The results also revealed increases in the total annual discharge and decreases in the 30-year mean of the peak annual discharge. Such climate-induced changes could have implications for water resources management in the region. The spatially and temporally varied hydro-climatic projections and their range of projections can be used for local-scale adaptation in this important water resource system for British Columbia. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The paper presents the results of laboratory triaxial compression tests to study the stiffness of very loose Fraser River sands. The stiffness has been shown to be very dependent on the time of confinement prior to shearing and the stress ratio at which the sample is aged. Higher stress ratios resulted in very low initial moduli with no ageing, but the moduli increased by several hundred percent during the first 1000 min of ageing. For ageing at a stress ratio of 1.0 (i.e., isotropic ageing), the initial moduli were higher than those for ageing at high stress ratios, but the stiffness increased by only about 60% during the first 1000 min of ageing. The rate of stiffness increase was approximately linear with the logarithm of time up to ageing times of 10 000 min (>1 week). Ageing at any stress ratio resulted in reduced contractive volumetric strain during subsequent shearing, reflecting a change in soil structure during ageing. The dℇ[sub v] /dℇ[sub a] ratio under triaxial compression loading decreased as the ageing stress ratio increased. The results suggest that close attention must be paid to the age of laboratory samples prepared to study the stress–strain response of sands at strains up to about 0.1%, particularly in studies on loose sand.Key words: sands, ageing, creep, modulus.Cet article présente les résultats d'un programme d'essais en laboratoire pour étudier la rigidité de sables très lâches du fleuve Fraser au moyen d'essais de compression triaxiale. On a montré que la rigidité était très dépendante du temps de confinement antérieur au cisaillement et du rapport des contraintes sous lequel l'échantillon a vieilli. Des rapports de contraintes plus élevés ont donné des modules initiaux très faibles sans vieillissement, mais les modules ont augmenté de plusieurs 100 % au cours des mille premières minutes de vieillissement. Sous un vieillissement isotrope, les modules initiaux étaient plus élevés que pour des rapports de contraintes plus élevés mais la rigidité a augmenté de seulement environ 60 % durant les 1000 premières minutes de vieillissement. La vitesse d'augmentation de la rigidité était approximativement linéaire en fonction du logarithme du temps jusqu'à des temps de vieillissement de 10 000 minutes (>1 semaine). Le vieillissement sous n'importe quel rapport de contraintes a donné des déformations volumétriques de contraction réduites durant le cisaillement subséquent, ce qui indiquait un changement dans la structure du sol durant le vieillissement. Le rapport dℇ[sub v] /dℇ[sub a] sous chargement triaxial en compression a diminué lorsque le rapport de contraintes de vieillissement augmentait. Les résultats suggèrent que l'on doit porter un attention particulière à l'âge des échantillons préparés en laboratoire pour étudier la réponse contrainte-déformation des sables jusqu'à des déformations de 0,1 %, particulièrement dans les études sur le sable lâche.Mots clés : sables, vieillissement, fluage, module.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Discusses a technique proposed for determining the in situ particle size distribution of suspended sediments in the Fraser River, British Columbia. Importance of the investigation for Fraser River; Key requirement for any field sampling of sediment particles; Factor attributed to the differences observed between the grain size proportions of flocs and primary particles. INSET: Closure, by Bommanna G. Krishnappan.

Focuses on the flow and sediment transport over a subaqueous dunes in Fraser River, British Columbia. Applicability of bedform phase diagrams in deep flows; Relation of lee side flow separation to dune morphology; Control of dune morphology by fluid flow and sediment transport.

Near William Lake, in the central interior of British Columbia, the Fraser River exposes long section of late Pleistocene Glaciolacustrine sediments selectively preserved within a bedrock trough. The dominant facies types are thick, normally graded gravels and sands that occupy steeply dipping multistory channels up to 300 m wide and several tens of metres deep. Channels appear to have been simultaneously cut and filled by high density turbidity currents in a glacial lake floored by stagnant ice. Fining upward sediment gravity flow sequences up to 50 m thick may be the product of quasi-continuous 'surging' turbidity flows triggered by catastrophic meltwater4 discharges into the trough or retrogressive failure of ice-cored sediments. Large-scale post-depositional deformation structures, such as synclinal folds, normal faults, sedimentary dyke swarms and dewatering structures, record gravitational foundering of sediment and pore-water expulsion caused by the melt of underlying glacier ice. Melting of buried ice masses along the floor of the trough appears to have controlled the flow paths of turbidity currents by producing sub-basins within the overlying sediment pile. An idealized model of 'supraglacial' lacustrine sedimentation is developed that may be applicable to other glaciated areas with similar bedrock topography. [ABSTRACT FROM AUTHOR]

A hierarchical typology for the channels and bars within aggradational wandering gravel-bed rivers is developed from an examination of a 50 km reach of lower Fraser River, British Columbia, Canada. Unit bars, built by stacking of gravelly bedload sheets, are the key dynamic element of the sediment transfer system, linking sediment transport during individual freshets to the creation, development and remoulding of compound bar platforms that have either a lateral or medial style. Primary and secondary unit bars are identified, respectively, as those that deliver sediment to compound bars from the principal channel and those that redistribute sediment across the compound bar via seasonal anabranches and smaller channels. The record of bar accretion evident in ground-penetrating radar sequences is consistent with the long-term development of bar complexes derived from historical aerial photographs. For two compound bars, inter-annual changes associated with individual sediment transport episodes are measured using detailed topographic surveys and longer-term changes are quantified using sediment budgets derived for individual bars from periodic channel surveys. Annual sediment turnover on the bars is comparable with the bed material transfer rate along the channel, indicating that relatively little bed material bypasses the bars. Bar construction and change are accomplished mainly by lateral accretion as the river has limited capacity to raise bed load onto higher surfaces. Styles of accretion and erosion and, therefore, the major bar form morphologies on Fraser River are familiar and consistent with those in gravelly braided channels but the wandering style does exhibit some distinctive features. For example, 65-year histories reveal the potential for long sequences of uninterrupted accretion in relatively stable wandering rivers that are unlikely in braided rivers. [ABSTRACT FROM AUTHOR]

Presents a study that examined the dunes and associated sand transport in a tidally influenced sand-bed channel in Fraser River, British Columbia. Methodology; Flow conditions and bed-form geometry; Dune migration and transport.

The Fraser River valley near Clinton contains a thick sediment fill that is presently incised down to bedrock. The sequence, approximately 500 m thick, is generally upward fining and consists of up to 100 m of glacigenic debris flow diamicton and glaciofluvial–deltaic gravel and sand at the base, overlain by about 350 m of glaciolacustrine sediments and minor diamicton, which is in turn capped by several metres of till. The sequence is interpreted to represent (i) valley aggradation in response to glaciation, followed by (ii) the impoundment of the valley by sediment and (or) ice, and the formation of a large proglacial lake(s), and finally (iii) overriding of the valley fill by glaciers. This glacial advance sequence can be readily correlated with previously studied units situated immediately to the north, most of which have been associated with the last glaciation; however, the age of these units has been based only on stratigraphic relations. We introduce limiting optical ages from a widespread glaciolacustrine unit that show that the glacial advance sequence was formed, at the earliest, during the penultimate Okanagan Centre Glaciation (oxygen isotope stage 4; ca. 74–59 ka), but almost certainly during the (last) Fraser Glaciation (oxygen isotope stage 2; ca. 24–12 ka). It could not have been deposited during oxygen isotope stage 6, or during an older glaciation.Près de Clinton, la vallée de la rivière Fraser est remplie d'épais sédiments qui sont présentement recoupés jusqu'au roc. La séquence, d'une épaisseur d'environ 500 m, est à affinement vers le haut et comprend jusqu'à 100 m de diamicton provenant d'écoulements de débris glaciogéniques et de sable et de gravier fluvio-glaciaire–deltaïque à la base, recouvert d'environ 350 m de sédiments glacio-lacustres et de diamictons mineurs qui sont à leur tour recouverts de plusieurs mètres de till. Selon notre interprétation, la séquence représente (i) l'accumulation dans la vallée, résultat de la glaciation, suivie (ii) du barrage de la vallée par les sédiments et (ou) de la glace et la formation d'un ou de plusieurs grands lacs glaciaires et finalement, (iii) une avancée glaciaire qui recouvre tout dans la vallée. Cette séquence d'avancée glaciaire peut être corrélée aisément à des unités localisées immédiatement au nord étudiées antérieurement. La plupart de ces unités ont été associées à la dernière glaciation; toutefois, l'âge de ces unités a seulement été basé sur des relations stratigraphiques. Nous introduisons des âges optiques limites provenant d'une unité glacio-lacustre de grande portée qui montre que la séquence d'avancée glaciaire a été formée, au plus tôt, au cours de l'avant-dernière glaciation de l'Okanagan-Centre (étape 4, isotope de l'oxygène; ca. 74–59 ka) mais presque assurément au cours de la (dernière) glaciation Fraser (étape 2, isotope de l'oxygène; ca. 24–12 ka). La séquence ne pourrait pas avoir été déposée durant l'étape 6 de l'isotope de l'oxygène, ni durant une glaciation antérieure.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the foraging behaviors of western sandpipers toward the invertebrates in the Fraser River estuary, British Columbia. Exclosure devices used to assess avian predation; Methodology used in the study; Discussion on the results of the study.

Deals with a study which measured the size distributions of suspended sediment particles under low flow conditions in the Fraser River, British Columbia using a submersible laser instrument. Description of the instrument; Measurement procedure; Results and discussion; Summary and conclusions.

We examine the oft-quoted relationship between the migration of Fraser River sockeye salmon around the northern end of Vancouver Island and sea surface temperatures. We examine the methods used to estimate the northern diversion and conclude that the estimates have a sufficiently low expected error to form a useful representation of sockeye salmon behaviour. The well-known relationship with Kains Island sea surface temperature is explored and problems are pointed out. In particular, we explore why Kains Island temperatures are good predictors of salmon behaviour in May when the sockeye can be over 1000 km away, but the coastal temperatures are poor predictors in July to September when the salmon are actually close by. We show that a more robust predictor can be developed using open ocean temperature fields and we show why Kains Island fails as a predictor during the summer months. Finally, we show by cross-validation that the northern diversion is predictable with an r.m.s. error of about 0.1. [ABSTRACT FROM AUTHOR]