Abstract Ground penetrating radar (GPR) is a popular technique for imaging and interpreting sedimentary architecture. However, current literature shows a wide range in the quality of information provided on the GPR methodology and processing technique. It is therefore difficult to judge the validity of the GPR interpretations and this produces inherent difficulties for comparison between surveys. This paper describes the key steps required to collect, process and interpret GPR surveys in sandy fluvial sediments. GPR data from the South Saskatchewan River, Canada, are used to illustrate each stage of data collection and processing. Particular attention is given to the appropriate set-up conditions for the GPR software and hardware, the selection of data-processing techniques and velocity analysis. Methods for the interpretation of GPR reflectors are also investigated using ground-truth control provided by a cut-face exposure. This paper presents recommendations for a systematic and rigorous methodology for the collection, processing and interpretation of GPR data in sandy fluvial environments. The paper suggests that all data-collection parameters and processing steps should be recorded or tabulated in any GPR publication to facilitate comparisons between surveys.

Abstract Flow dynamics at river channel confluences can be characterized by six major regions of flow stagnation, flow deflection, flow separation, maximum velocity, flow recovery and distinct shear layers. The dominant controls upon the magnitude of these regions are shown to be the junction angle and the ratio of discharges between the confluent channels. Through the combined use of scaled laboratory modelling and an analysis of field evidence, the dynamics of flow are found to produce a confluence morphology which consists of avalanche faces at the mouth of each confluent channel, a deep central scour and a bar within the separation zone. Tracing of sediment in both laboratory and natural channels reveals distinct sediment pathways within the junction which can be explained through the model of flow dynamics. A knowledge of confluence flow dynamics is important when assessing channel design criteria, junction bed morphology and ancient confluence sediments.