Loading...
Spatial and temporal analysis of compensational stacking and gradual migration of an experimental debris-flow fan
Brown, Hayden Edward
Brown, Hayden Edward
Citations
Altmetric:
Editor
Date
Date Issued
2016
Date Submitted
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
Abstract
Understanding sediment transport across debris-flow fans is crucial for assessment and mitigation of debris flow hazards in mountainous communities. To gain a better understanding of sediment transport, an experimental debris-flow fan was developed from 30 successive experimental debris flow events. The debris flow material used was a kaolinite sand slurry consisting of 19% kaolinite, 48% sand and 33% water (all percentages are by mass), designed to model the Bingham plastic properties of natural debris flow. This experimental debris-flow fan was developed to analyze compensational stacking, which is the tendency of a deposit to fill a topographic low to reduce the overall potential energy of the system, and to evaluate overall flow directions of debris flow events as a debris-flow fan evolves. Specifically, the spatial variation of compensational stacking was analyzed longitudinally, by mapping 32 cross-sections from the apex of the fan to the toe of the fan, and calculating the modified compensation index for each cross-section. The overall flow directions and altering of flow direction was analyzed from video data, oblique birds-eye photographic data, and from a developed metric called net migration. Net migration evaluates, in two-dimensions, how much of a debris-flow mass is to the left or right of an assumed central axis to depict gradual migration of the experimental debris flow trials throughout the experiment. Several geometric and physical properties of the flow events were measured, including run-out length, length to width ratio, frontal velocity, longitudinal slope, and margin slope, in order to perform various correlation analyses with the modified compensation index and the net migration metric. The analyses were used to identify what influences movement and propagation of debris-flow events across the fan surface. Also, time series as related to net migration, were analyzed using cross-correlation, autocorrelation, partial autocorrelation, and autoregressive integrated moving average (ARIMA) modelling to evaluate evolution of the debris-flow fan surface over time, and how this time component affects the flow directions of events. It was found that the modified compensation index and net migration metric exhibit exponential decay as one moves closer to the apex of the debris flow fan. Also, it was found that net migration exhibits cyclical amplified behavior, whereby successive events move laterally across the fan surface in a back and forth manner, and this behavior is amplified through time. These findings are valuable for engineers and scientists, because they can help better predict locations of future debris-flow events on fan surfaces, and more effectively implement and locate mitigation structures.
Associated Publications
Rights
Copyright of the original work is retained by the author.