Towards a new generation of fluvial facies models for the interpretation of ancient deposits, based on inter-annual peak discharge variance of modern rivers

Fielding, Christopher R., Alexander, Jan ORCID: https://orcid.org/0000-0002-2830-2727 and Argiro, Adam (2024) Towards a new generation of fluvial facies models for the interpretation of ancient deposits, based on inter-annual peak discharge variance of modern rivers. Sedimentology. ISSN 0037-0746

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Abstract

Fluvial facies models based on river planform are flawed and not fully fit for purpose. An alternative approach to classifying fluvial deposits is based on river discharge characteristics. A recent paper showed that the co-efficient of variance of annual peak discharge (CVQp) correlates well with the characteristics of preserved alluvium for a suite of modern rivers. Here, the database of rivers is expanded and augmented, and the utility of this statistic confirmed. For modern rivers, plotting the running-value of CVQp for a set interval (for example, 30 years) over a longer discharge record shows that the statistic varies both spatially and temporally. The CVQp can rise abruptly at a given location in response to a single flow event if that event is significantly larger than is common in that river. Such abrupt changes in CVQp are superimposed on longer-term patterns of more gradual change stimulated by environmental factors or anthropogenic effects such as dam construction. If the period of calculation for CVQp is relatively short, ‘anomalous’ events appear more frequently. Sequential studies of modern rivers indicate that such anomalous events have a high probability of being preserved in the alluvial record of the river, and suggest that, over the timeframes of channel filling and abandonment, they may constitute the dominant (characteristic) portion of the record in high CVQp systems. Since flow events with strongly peaked hydrographs (flashy discharges) are more common in high CVQp systems and leave a record dominated by upper flow regime stratification styles, it follows that the alluvial record of high CVQp rivers will be dominated by upper flow regime stratification. In contrast, in lower CVQp systems the occurrence of an event that changes the running CVQp value significantly may form a distinct event deposit, and the temporarily changed CVQp is unrepresentative for the duration of the channel’s life. The dominance of upper flow regime stratification, together with decreased preservation of identifiable macroform structure, increased lateral lithological heterogeneity, and in many cases increased preservation of in situ tree fossils in channel deposits of higher CVQp rivers, forms the basis for a series of new facies models for low, moderate, high, and very high/ultra-high CVQp alluvial systems and deposits. The new models can be applied to ancient successions either in combination with traditional, planform-based models, or not. These models provide information about ancient palaeoenvironmental conditions, and changes in such conditions over time at various scales via stratigraphic investigations.

Item Type:	Article
Additional Information:	DATA AVAILABILITY STATEMENT: A lot of data used in the analysis for this paper were sourced via The Global Runoff Data Centre, 56 068 Koblenz, Germany (https://grdc.bafg.de/GRDC/EN/02_srvcs/21_tmsrs/riverdischarge_node.html) accessed multiple times through 2023–2024. Components of those data originated from a large number of organizations including: Argentina – the Subsecretaría de Recursos Hídricos (SRH). Brazil – National Water Agency (ANA) and the Operador Nacional do Sistema Elétrico (ONS). South Africa – Department of Water and Sanitation (DWA) Namibia – Ministry of Agriculture, Water & Forestry. Japan – Infrastructure Development Institute (IDI). Malaysia – Department of Irrigation and Drainage. Oman – Ministry of Regional Municipalities, Environment & Water Resources (MRMWR). Most of the Australian data were extracted from the Australian Bureau of Meteorology Hydrologic Reference stream gauging Stations (http://www.bom.gov.au/water/hrs/index.shtml) on various dates through 2023–2024 (including some original discharge data from QLD – Department of Regional Development, Manufacturing and Water, NT – Department of Environment, Parks and Water Security). Burdekin river data were supplied by the Queensland Department of Natural Resources and Mines. American data were sourced from the USGS data base (nwis.waterdata.usgs.gov/nwis) accessed on several dates through 2023 and 2034. British river data were obtained from the from the National River Flow Archive Search Data | National River Flow Archive (ceh.ac.uk) accessed on various dates through 2023–2024. Some data for Canadian rivers were sourced from the Environment and Climate Change Canada Historical Hydrometric Data web site (https://wateroffice.ec.gc.ca/mainmenu/historical_data_index_e.html) on various dates in 2023. Ob River data are available from http://www.r-arcticnet.sr.unh.edu/ObservedAndNaturalizedDischarge-Website/. Some data for the Jamuna River were taken from Rahman (2016). A summary of all data used in this analysis is given in Table S1.
Uncontrolled Keywords:	alluvial,discharge variability,fluvial facies models,planform,preservation potential
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Geosciences
Depositing User:	LivePure Connector
Date Deposited:	24 Sep 2024 12:55
Last Modified:	07 Oct 2024 19:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/96796
DOI:	10.1111/sed.13234

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