TY - JOUR
T1 - A shifting ‘river of sand’
T2 - The profound response of Australia's Warrego River to Holocene hydroclimatic change
AU - Larkin, Z. T.
AU - Ralph, T. J.
AU - Tooth, S.
AU - Duller, G. A.T.
N1 - Funding Information:
ZL was supported by an Australian Postgraduate Award scholarship. Fieldwork and laboratory costs were supported by Macquarie University postgraduate research funds, a British Society for Geomorphology Postgraduate Research Grant awarded to ZL, and a Macquarie University Research and Development Grant awarded to TR. Adam Wethered is thanked for assistance in the field. Hollie Wynne is thanked for processing the OSL samples at Aberystwyth University. Thanks also go to landholders Wally Dunstan from Hortonvale station and Paul McCarthy from Hayfield station for permission to access field sites on their properties. We also thank two anonymous reviewers for their thorough and constructive comments that helped us to clarify our arguments and improve the paper.
Funding Information:
ZL was supported by an Australian Postgraduate Award scholarship. Fieldwork and laboratory costs were supported by Macquarie University postgraduate research funds, a British Society for Geomorphology Postgraduate Research Grant awarded to ZL, and a Macquarie University Research and Development Grant awarded to TR. Adam Wethered is thanked for assistance in the field. Hollie Wynne is thanked for processing the OSL samples at Aberystwyth University. Thanks also go to landholders Wally Dunstan from Hortonvale station and Paul McCarthy from Hayfield station for permission to access field sites on their properties. We also thank two anonymous reviewers for their thorough and constructive comments that helped us to clarify our arguments and improve the paper. Inundation extent and frequency data created by Mueller et al. (2016) are publicly available from the Australian Flood Risk Information Portal (www.ga.gov.au/wofs). Monthly Southern Oscillation Index (SOI) data and annual rainfall data for the Carnarvon rainfall station (35018) was sourced from the Australian Bureau of Meteorology (http://www.bom.gov.au/climate/data/?ref=ftr). Hydrological time-series data were sourced from the Queensland Government Water Information System (Department of Natural Resources et al. 2018), and the New South Wales Department of Primary Industries Office of Water (Water, 2018). The data that support the findings of this paper are available from the corresponding author upon reasonable request.
Publisher Copyright:
© 2020
PY - 2020/12/1
Y1 - 2020/12/1
N2 - In dryland river catchments, palaeochannels provide some of the key records for understanding the changes in river character and behaviour that can occur in response to different extrinsic and intrinsic controls. Here, we combine modern hydroclimatic datasets, satellite imagery, field surveys, and optically stimulated luminescence (OSL) dating of palaeochannels to investigate the response of the ~850 km long Warrego River, located in central eastern Australia, to Holocene hydroclimatic change. The modern Warrego is an intermittent to ephemeral, low energy river (unit stream power, ω, ≤4 W m−2), and is characterised by low sinuosity (‘straight’), narrow (<50 m), single-thread, anabranching, and distributary channels that transport fine-grained (dominantly mud and sand) sediment. Marked downstream declines in discharge and stream power mean that many channels are discontinuous, terminating downstream at floodouts or in unchannelled floodplain wetlands before reaching the Darling River. By contrast, OSL ages and palaeohydrological reconstructions show that between ~8 and 5 ka, higher energy (~8–10 W m−2), wider (~160 m), meandering channels were the characteristic river style. In the Burrenbilla and Coongoola palaeochannels, prevailing La Niña conditions were likely responsible for bankfull discharges between 3 and 59 times those of the modern river, which probably enabled the palaeochannels to maintain perennial flow in continuous courses to the Darling River. After ~5 ka, El Niño events became stronger and more frequent, leading to greater catchment aridity and lower, more variable, river discharges. These extrinsic changes resulted in intrinsic adjustments to river character and behaviour, with key geomorphic thresholds being crossed in the cessation of meandering and establishment of the modern single-thread, anabranching, and distributary channels. The Warrego River's dramatic pattern transformation in response to mid- to late Holocene hydroclimatic change has similarities with some other Australian dryland river responses over equivalent timeframes. The pattern transformation demonstrates the Warrego River's sensitivity to extrinsic forcing and represents one of the most profound dryland river changes in the late Quaternary.
AB - In dryland river catchments, palaeochannels provide some of the key records for understanding the changes in river character and behaviour that can occur in response to different extrinsic and intrinsic controls. Here, we combine modern hydroclimatic datasets, satellite imagery, field surveys, and optically stimulated luminescence (OSL) dating of palaeochannels to investigate the response of the ~850 km long Warrego River, located in central eastern Australia, to Holocene hydroclimatic change. The modern Warrego is an intermittent to ephemeral, low energy river (unit stream power, ω, ≤4 W m−2), and is characterised by low sinuosity (‘straight’), narrow (<50 m), single-thread, anabranching, and distributary channels that transport fine-grained (dominantly mud and sand) sediment. Marked downstream declines in discharge and stream power mean that many channels are discontinuous, terminating downstream at floodouts or in unchannelled floodplain wetlands before reaching the Darling River. By contrast, OSL ages and palaeohydrological reconstructions show that between ~8 and 5 ka, higher energy (~8–10 W m−2), wider (~160 m), meandering channels were the characteristic river style. In the Burrenbilla and Coongoola palaeochannels, prevailing La Niña conditions were likely responsible for bankfull discharges between 3 and 59 times those of the modern river, which probably enabled the palaeochannels to maintain perennial flow in continuous courses to the Darling River. After ~5 ka, El Niño events became stronger and more frequent, leading to greater catchment aridity and lower, more variable, river discharges. These extrinsic changes resulted in intrinsic adjustments to river character and behaviour, with key geomorphic thresholds being crossed in the cessation of meandering and establishment of the modern single-thread, anabranching, and distributary channels. The Warrego River's dramatic pattern transformation in response to mid- to late Holocene hydroclimatic change has similarities with some other Australian dryland river responses over equivalent timeframes. The pattern transformation demonstrates the Warrego River's sensitivity to extrinsic forcing and represents one of the most profound dryland river changes in the late Quaternary.
KW - Channel breakdown
KW - Geomorphic thresholds
KW - Palaeochannel
KW - River pattern
UR - http://www.scopus.com/inward/record.url?scp=85090410039&partnerID=8YFLogxK
U2 - 10.1016/j.geomorph.2020.107385
DO - 10.1016/j.geomorph.2020.107385
M3 - Article
AN - SCOPUS:85090410039
SN - 0169-555X
VL - 370
JO - Geomorphology
JF - Geomorphology
M1 - 107385
ER -