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Post rock-avalanche dam outburst flood sedimentation in Ram Creek, Southern Alps, New Zealand.

Lookup NU author(s): Dr Stuart Dunning

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Abstract

Rock avalanches are common in mountainous regions that are tectonically active. They are capable of forming natural dams of uncertain persistence that have significant impacts on the river system over wide spatial scales and possibly over geological time scales. Here we combine field data and digital elevation model (DEM) analysis to show the response of Ram Creek, New Zealand, to 28 years of sediment dispersion following the 1968 emplacement of a co-seismic, rock-avalanche dam that breached catastrophically in 1981. The results show a system that has not attained equilibrium, being unable to move the quantity of dam-derived sediments, and will likely not attain equilibrium before the next major sediment input; it is in a state of persistent disturbance where localised reworking dominates. Erosion in Ram Creek is focussed on lateral bevelling and bedrock gorge widening rather than vertical incision to keep pace with tectonic uplift. Importantly for studies of tectonic geomorphology, this widening — which if sustained will form a strath terrace — does not represent a period of reduced uplift. Stream metrics (concavity and steepness) are unable to differentiate the identified rock-avalanche-induced knickpoint from tectonic and lithological knickpoints.


Publication metadata

Author(s): Harrison LM, Dunning SA, Woodward J, Davies TRH

Publication type: Article

Publication status: Published

Journal: Geomorphology

Year: 2015

Volume: 241

Pages: 135-144

Print publication date: 15/07/2015

Online publication date: 17/04/2015

Acceptance date: 30/03/2015

Date deposited: 06/10/2015

ISSN (print): 0169-555X

ISSN (electronic): 1872-695X

Publisher: Elsevier

URL: http://dx.doi.org/10.1016/j.geomorph.2015.03.038

DOI: 10.1016/j.geomorph.2015.03.038


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