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Facies relationships in Pleistocene braided outwash deposits in southern Ontario demonstrate the presence of a large braid bar with adjacent side channel. The core of the bar is up to 6 m high, and consists of crudely horizontally stratified gravels. Downstream from the core is the bar front facies, consisting of large gravelly foresets up to 4 m high, rounded off in many places by reactivation surfaces. Upstream from the core is the bar stoss side facies consisting of several sets (individually up to 35 cm thick) of tabular cross-bedding, arranged in coarsening-upward sequences. The stoss side-core-bar front relationships are continuously exposed in one 400 m long quarry face which is cut almost parallel to the palacoflow direction. A transverse quarry face shows the side channel facies, which consists if trough cross-bedded sands. Gravel layers can be seen to finger from the main gravelly bar into the sandy side channel, but they do not reach the base of the channel. This surprising relationship indicates that gravel moved only in the topographically higher parts of the system. After deposition in the side channel, and growth upstream and downstream from the bar core, the entire system aggraded. Crudely horizontally stratified, and imbricaled gravel sheets were laid down as a bar top facies. Grain size analyses indicate strongly bimodal distributions, implying that much of the sand in the spaces between pebbles and boulders filtered in after the gravel had been deposited. This interpretation is strengthened by velocity calculations—mean velocities in excess of 300 cm/s would be needed to roll the gravel as bed load, but at such a velocity, a large amount of sand would be transported entirely in suspension. In a final section of the paper, our results are combined with other work on braided systems in an attempt to formulate a more general facies model. [ABSTRACT FROM AUTHOR]

The flood cycle of an arroyo in southwestern United States exhibits three separate stages: 1) the flood stage, often turbulent and violent, and impossible to study as it occurs; 2) the immediate after-flood stage, exhibiting conspicuous and interesting patterns, of which some may be observed; and 3) the dry stage, an indefinite period which lasts until the next flood, during which stage some detailed mechanisms of transport patterns may be observed. From this dry stage, aided by schematic and fugitive impressions gamed during the other two stages, systematic inferences may be drawn concerning the mechanisms involved in transport throughout the cycle. Schematic illustrations support the analysis and categorization of the several mechanisms and their transport-sedimentation activities in this paper. The flood stage thoroughly reworks the channels within a valley, rearranging the whole transport load of sediments. At the moment the flood begins to wane the heaviest elements of the whole load are dropped in a series of primary patterns arranged in steps up the longitudinal profile of the stream, dependent upon the nature of the channel, the volume of flow, and the velocity of the flood. The late waters of the after-flood stage readjust the attitudes of the channel, and resort the finer materials, perhaps systematically placing them on and between the steps of the profile. As the late waters continue to wane in volume the finest materials are finally resorted arid arranged into the minor forms with in the channel, to endure as sedimentation forms until the next flood occurs.

This paper is respectfully dedicated to Brian Haywood and André Grenier, of the McGill Sub-Arctic Research Laboratory, who lost their lives on the Korok River in northern Labrador-Ungava while engaged in filed research. [ABSTRACT FROM AUTHOR]

The paper describes tests made on a small river to examine the practicability of measuring quantitatively, by tracer methods, sand transport occurring over a rippled bed in a natural channel. Three principal tracer methods, all previously verified under steady flow conditions in a laboratory channel, and identified as the spatial integration, time integration and steady dilution methods, were examined by introducing radioactive and fluorescent tracers to represent a narrow size fraction of the bed sand. The serious limitations of the time integration and steady dilution methods under conditions of unsteady solids discharge were exposed by a sudden flood discharge occurring during the course of the study. An approximate method, based on the time integration approach, but also requiring some spatial tracer data, is suggested, whereby an estimate of the transport is possible in the case of highly variable sand discharge. However, it is seen that in the sand case, the spatial integration method offers the most workable and informative tracer method for use in natural rivers. The results, by this method, were generally consistent with those given by the summation of the measured suspended-solids flux and the transport occurring either by surface creep or in close vicinity to the bed. The latter quantity is determined from the downstream advance of the ripple bed-forms, and methods are described for its derivation from ultrasonic echo sounder records of bed profiles. Finally sand transport values are calculated for a number of river discharges and for two laboratory Channel tests using various well-known computational procedures -- Einstein, Bagnold, modified Einstein, Meyer-Peter and Muller, and Laursen procedures. Significant differences in the computed values for individual flow conditions are observed. [ABSTRACT FROM AUTHOR]