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Title:
Intrinsic vs. extrinsic controls on channel evolution in a sub-tropical river, Australia
Authors:
Daley, James; Croke, Jacky; Thompson, Chris; Cohen, Tim; Macklin, Mark; Sharma, Ashneel
Affiliation:
AA(School of Geography, Planning and Environmental Management, the University of Queensland, Brisbane, Australia ), AB(School of Geography, Planning and Environmental Management, the University of Queensland, Brisbane, Australia ), AC(School of Geography, Planning and Environmental Management, the University of Queensland, Brisbane, Australia ), AD(GeoQuEST Research Centre - School of Earth and Environmental Sciences, University of Wollongong, Wollongong, Australia), AE(Centre for Catchment and Coastal Research and the River Basin Dynamics and Hydrology Research Group, Department of Geography and Earth Sciences, Aberystwyth University, Ceredigion, United Kingdom), AF(Department of Science, Information Technology and Innovation, Queensland Government, Australia)
Publication:
EGU General Assembly 2016, held 17-22 April, 2016 in Vienna Austria, id. EPSC2016-13780
Publication Date:
04/2016
Origin:
COPERNICUS
Bibliographic Code:
2016EGUGA..1813780D

Abstract

Palaeohydrological research provides valuable insights to the understanding of short- and long-term fluvial dynamics in response to climate change and tectonic activity. In landscapes where tectonic activity is minimal fluvial archives record long-term changes in sediment and discharge dynamics related to either intrinsic or extrinsic controls. Isolating the relative controls of these factors is an important frontier in this area of research. Advances in geochronology, the acquisition of high resolution topographic data and geomorphological techniques provide an opportunity to assess the relative importance of intrinsic and extrinsic controls on terrace and floodplain formation. This study presents the results of detailed chrono-stratigraphic research in a partly confined river valley in subtropical southeast Queensland. River systems within this region are characterized by high hydrological variability and have a near-ubiquitous compound channel morphology (macrochannel) where Holocene deposits are inset within late Pleistocene terraces. These macrochannels can accommodate floods up to and beyond the predicted 100-year flood. Using single grain optically stimulated luminescence and radiocarbon analyses, combined with high resolution spatial datasets, we demonstrate the nature of fluvial response to major late Quaternary climate change. A large proportion of the valley floor is dominated by terrace alluvium deposited after the Last Glacial Maximum (LGM) (17 - 13 ka) and overlies basal older Pleistocene alluvium. Preliminary results suggest a phase of incision occurred at 10 ka with the formation of the large alluvial trench. The Holocene floodplain is dominated by processes of catastrophic vertical accretion and erosion (cut-and-fill) and oblique accretion at the macrochannel margins. The consistency in ages for the terraces and subsequent incision suggests a uniform network response. Alluvial sediments and channel configuration in this compound and complex landscape represent a discernable response to long-term climate change, high climate variability and extreme weather events.
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