Evidence of self-organized criticality in riverbank mass failures: a matter of perspective?

Croke, Jacky, Denham, Robert, Thompson, Chris and Grove, James (2015) Evidence of self-organized criticality in riverbank mass failures: a matter of perspective?. Earth Surface Processes and Landforms, 40 7: 953-964. doi:10.1002/esp.3688


Author Croke, Jacky
Denham, Robert
Thompson, Chris
Grove, James
Title Evidence of self-organized criticality in riverbank mass failures: a matter of perspective?
Journal name Earth Surface Processes and Landforms   Check publisher's open access policy
ISSN 1096-9837
0197-9337
Publication date 2015
Sub-type Article (original research)
DOI 10.1002/esp.3688
Open Access Status
Volume 40
Issue 7
Start page 953
End page 964
Total pages 12
Place of publication Chichester, West Sussex, United Kingdom
Publisher John Wiley and Sons
Collection year 2016
Language eng
Abstract A growing body of field, theoretical and numerical modelling studies suggests that predicting river response to even major changes in input variables is difficult. Rivers are seen to adjust rapidly and variably through time and space as well as changing independently of major driving variables. Concepts such as Self-Organized Criticality (SOC) are considered to better reflect the complex interactions and adjustments occurring in systems than traditional approaches of cause and effect. This study tests the hypothesis that riverbank mass failures which occurred both prior to, and during, an extreme flood event in southeast Queensland (SEQ) in 2011 are a manifestation of SOC. Each wet-flow failure is somewhat analogous to the 'avalanche' described in the initial sand-pile experiments of Bak et al. (Physical Review Letters, 1987, 59(4), 381-384) and, due to the use of multitemporal LiDAR, the time period of instability can be effectively constrained to that surrounding the flood event. The data is examined with respect to the key factors thought to be significant in evaluating the existence of SOC including; non-linear temporal dynamics in the occurrence of disturbance events within the system; an inverse power-law relation between the magnitude and frequency of the events; the existence of a critical state to which the system readjusts after a disturbance; the existence of a cascading processes mechanism by which the same process can initiate both low-magnitude and high-magnitude events. While there was a significant change in the frequency of mass failures pre- and post-flood, suggesting non-linear temporal dynamics in the occurrence of disturbance events, the data did not fit an inverse power-law within acceptable probability and other models were found to fit the data better. Likewise, determining a single 'critical' state is problematic when a variety of feedbacks and multiple modes of adjustment are likely to have operated throughout this high magnitude event. Overall, the extent to which the data supports a self-organized critical state is variable and highly dependent upon inferential arguments. Investigating the existence of SOC, however, provided results and insights that are useful to the management and future prediction of these features.
Keyword Bank erosion
Lockyer Valley
Queensland
Self-Organized Criticality (SOC)
Wet-flow mass failures
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Geography, Planning and Environmental Management Publications
Official 2016 Collection
 
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