[1] Methodologies are presented to (1) evaluate the effect of acoustic Doppler current profiler (ADCP) motion on velocity measurements, (2) assess the stationarity of velocity time series, and (3) ensure that a sample record is of sufficient length for measurements taken with an ADCP at a fixed location in a natural river. ADCP motion occurring on the timescale of an ensemble is investigated by comparing single-ping and multiping measurements obtained at the same location under the same flow conditions. Large-scale motion occurring over the course of the entire measurement is studied by first examining a set of indicators to determine if motion may have resulted in the ADCP measuring in regions of different flow characteristics and then dividing the record into segments representing the potentially different regions for comparison. If boat motion is significant, the ADCP record is edited accordingly. Stationarity is assessed using statistical trend tests with guidance provided for selecting parameters based on instrument physics and flow conditions. Mean streamwise and spanwise velocity profiles can be calculated after confirming the reliability of a measurement. A set of criteria are presented to evaluate the appropriateness of an assumption of the law of the wall for streamwise velocity profiles. The methodology is demonstrated using 67 fixed-vessel measurements obtained at two sites on the lower Roanoke River for two discharges. The results indicate that an appropriate procedure was used for securing the ADCP in the channel and that the sample records were sufficient to provide both accurate measurements of mean quantities and assess the stationarity of velocity.

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As a part of the settling and self-weight consolidation of fine-grained materials, a common but not widely recognized phenomenon randomly occurs, namely channeling or the formation of narrow vertical paths or “channels.” Channel formation can have important effects on the microstructure, consolidation, and shear strength characteristics of newly formed sediments. However, only a few studies have been performed on channeling. The causes of channel formation and the factors affecting it are still not fully understood. This paper presents the results of an experimental study of channel formation during settling and self-weight consolidation in fine-grained materials. Four types of fine-grained materials and different slurry concentrations were tested using large and small settling columns, and channel formation was observed using a high-resolution digital camera. The results indicate that the primary mechanism for channel formation is the coalescence of small-scale discontinuities between clusters of soil particles formed by flocculation. The stronger the degree of flocculation, the more prevalent is the formation of channels. Pore pressure measurements show the effects of channels in dissipating excess pore pressures in sediments undergoing self-weight consolidation.