Water discharge and sediment flux intermittency in the fluvial Escanilla Formation, Spain: Implications for changes in stratigraphic architecture

Sharma, Nikhil; Whittaker, Alexander C.; Adatte, Thierry; Castelltort, Sébastien

doi:10.1002/dep2.272

Cited by 3 publications

(1 citation statement)

References 85 publications

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“…This implies that during periods of low flow, the coarse-grained sediment particles were likely not in transport throughout the rest of the year. This is consistent with interpretations of intermittency values determined for both modern and ancient streams (Hayden et al, 2021;Sharma et al, 2024), thereby highlighting the importance of a few high magnitude discharge events during which effective sediment transport occurs, in both, arid and humid environments (Leenman et al, 2022;Molnar, 2001).…”

Section: Grain Size Trends and Intermittencies Of Oligo-miocene Alluv...supporting

confidence: 88%

Quantification of sediment fluxes and intermittencies from Oligo–Miocene megafan deposits in the Swiss Molasse basin

Garefalakis,

do Prado,

Whittaker

et al. 2024

Basin Research

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The conglomerates preserved in alluvial fans in the Swiss Molasse basin provide crucial insights into the sedimentary dynamics of these routing systems. In particular, the architectural trends and grain sizes of such deposits reveal information on the sediment fluxes and record variations in the intermittency — a proxy for the fan's activity — that indicate on the relative importance of tectonic or climatic controls on sediment production and transport. Here, we calculated intermittencies from sediment transport dynamics using the ratio between the long‐term average and the short‐term instantaneous unit sediment fluxes during bankfull discharge conditions. For this, we collected grain size data from three palaeo‐fan systems that were active through Oligo–Miocene times and that reveal preserved proximal–distal relationships. The three fan systems, which we term the western, central and eastern fans, show significant differences in their long‐term sediment budget but equivalent magnitudes of the sediment transport dynamics expressed through the intermittency factor. The eastern fan records a low long‐term sediment flux (5.7 km2 Myr−1), which needed the fan to be active during ca. 8 h yr−1 (intermittency factor of 0.89 × 10−3). The western fan reveals a higher long‐term sediment flux (16.2 km2 Myr−1), which could have accumulated during ca. 16 h yr−1 (intermittency factor of 1.83 × 10−3), thereby reflecting a more active system. The central fan records the largest long‐term sediment flux (40.3 km2 Myr−1), where ca. 57 h yr−1 of sediment transport would be required to deposit the supplied material (intermittency factor of 6.53 × 10−3), thus representing the most active system. By relating these characteristics to the regional exhumation history, we consider that the central fan mainly recorded the transient response of the Alpine surface to the break‐off of the European mantle lithosphere slab. Contrarily, the western and eastern fans were formed during the Alpine evolution when steady‐state conditions between uplift and erosion were reached and when sediment fluxes to the basin were lower. Despite differences in the tecto‐geomorphic and climatic boundary conditions, our data suggest that these Oligo–Miocene megafans could accomplish their mean annual sediment transport work within a few hours or days per year.

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Section: Grain Size Trends and Intermittencies Of Oligo-miocene Alluv...supporting

confidence: 88%

Quantification of sediment fluxes and intermittencies from Oligo–Miocene megafan deposits in the Swiss Molasse basin

Garefalakis,

do Prado,

Whittaker

et al. 2024

Basin Research

Self Cite

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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,

Alexander,

Argiro

2024

Sedimentology

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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.

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Landscapes on the edge: River intermittency in a warming world

McLeod,

Whittaker,

Bell

et al. 2024

Geology

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Sediment transport in rivers is not steady through time. Highly intermittent river systems, which only transport bedload during the most significant flow events, are particularly sensitive to changes in climate and precipitation patterns. People and landscapes can be vulnerable to fluvial processes, and quantifying river intermittency is critical for assessing landscape response to projected changes in precipitation extremes due to climate change. We generated new constraints on recent to modern fluvial intermittency factors—the frequency at which bedload is mobilized in a river—based on field measurements in the Corinth Rift, Greece, and Holocene sediment accumulation rates. Results reveal some of the lowest documented intermittency factors to date, showing Mediterranean rivers can transport an entire annual sediment load in a rare storm event. Coupling intermittency calculations with historical flood and precipitation data indicates these rivers transport bedload during one storm every ∼4 yr, associated with rainfall >50 mm/d, and subsequent floods; this hydroclimate is typical across the Mediterranean region. Furthermore, climate models predict precipitation extremes will increase across Europe, and the frequency of events that surpass thresholds of sediment transport will increase significantly, potentially causing sediment loads to double by 2100 CE. As the area of arid land likely to host intermittent rivers also increases, sensitive landscapes are on the edge of significant geomorphic change, driven by global warming.

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Water discharge and sediment flux intermittency in the fluvial Escanilla Formation, Spain: Implications for changes in stratigraphic architecture

Cited by 3 publications

References 85 publications

Quantification of sediment fluxes and intermittencies from Oligo–Miocene megafan deposits in the Swiss Molasse basin

Quantification of sediment fluxes and intermittencies from Oligo–Miocene megafan deposits in the Swiss Molasse basin

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

Landscapes on the edge: River intermittency in a warming world

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