Events, episodes, and phases: Signal from noise in flood-sediment archives

Toonen, W.H.J.; Foulds, Simon; Macklin, Mark G.; Lewin, John

doi:10.1130/g38540.1

Cited by 34 publications

(31 citation statements)

References 36 publications

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“…However, improving our understanding of sedimentary function in overbank environments is an important goal across a variety of disciplines. Information about temporal trends in the channel to overbank sediment ratio of a river's deposit can provide important context to stratigraphic reconstructions across climate boundaries (e.g., Foreman et al 2012), and could factor in to global predictions of fluvial response to climate change (Toonen et al 2017). Further, sequence stratigraphic reconstructions of alluvial successions along continental margins (e.g., Huerta et al 2011;Marenssi et al 2015) will be improved by considering hydrograph variability in the context of the existing allogenic forcings of accommodation and sediment supply.…”

Section: Introductionmentioning

confidence: 99%

Sediment Storage Partitioning in Alluvial Stratigraphy: The Influence of Discharge Variability

Esposito

Leonardo

Harlan

et al. 2018

Journal of Sedimentary Research

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Numerical models of formation of alluvial stratigraphy often specify, either explicitly or implicitly, the proportion of channel and overbank sediments that are deposited during a given interval of time. However, little is known about the factors that affect the partitioning of sediment between channels and the overbank environment over long time intervals, and the fidelity with which that partition is preserved in the stratigraphic record. Here we use physical experiments to investigate the role that discharge variability plays in this partitioning in fluvial stratigraphy. We find that channels formed under constant flow conditions have low lateral mobility and act mostly as conduits for sediments to reach the shoreline. The bulk of the aggradation in this case is derived from sediment-laden flow that escapes the main channels. By contrast, including floods increases channel lateral mobility, and this change is recorded in stratigraphy as an increased proportion of channel deposits relative to overbank deposits. When variable flow is included as an input condition a large volume of in-channel deposition occurs, rendering the channels substantial contributors to stratigraphic volume on their own. The increase in channel deposit volume is driven mainly by a threefold increase in the average time that a location is subject to in-channel aggradation. Other factors include a slight increase of in-channel aggradation rates, and an increase in erosion of the overbank environment that results from energetic overbank flows. Our study shows that the character of a river's hydrograph exerts a significant influence on the proportion of channel to overbank sediment bodies in alluvial successions, which is an unexamined source of uncertainty in common stratigraphic models.

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Section: Introductionmentioning

confidence: 99%

Sediment Storage Partitioning in Alluvial Stratigraphy: The Influence of Discharge Variability

Esposito

Leonardo

Harlan

et al. 2018

Journal of Sedimentary Research

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“…These records provide a tool to place recorded extreme events in a framework of long-term flooding variability. Moreover, longer flood series allow detection of distinctive phases and episodes of flooding in addition to individual events (Toonen et al, 2017), which allows comparison with other regional hydroclimatic and biological records (e.g. Norton et al, 1989;Richardson et al, 2013;Fuller et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Storm-generated Holocene and historical floods in the Manawatu River, New Zealand

et al. 2018

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This paper reports the first reconstruction of storm-generated late Holocene and historical river floods in the North Island of New Zealand. The sedimentary infills of nine palaeochannels were studied in the lower alluvial reaches of the Manawatu River. Floods in these palaeochannels were recorded as a series of sand-rich units set within finer-grained fills. Flood chronologies were constrained using a combination of radiocarbon dating, documentary sources, geochemical markers, and palynological information. Flood units were sedimentologically and geochemically characterised using high resolution ITRAX TM X-Ray Fluorescence (XRF) core scanning and laser diffraction grain-size analysis. The longest palaeoflood record extends back ca.3000 years. The temporal resolution and length of the Manawatu record reflects accommodation space for fluvial deposits, channel dynamics and mobility, and high sediment supply. Floods that occurred in the Manawatu during the mid-1800s at the time of European land clearance and in the first decade of the twentieth century appear to be among the largest recorded in the last 3000 years.

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“…For example, the signal shredding idea (Jerolmack & Paola, ) is based on the sediment flux attribute only and suggests that sediment storage and release by autogenic processes in the channel will mask or destroy the signal S A from the upstream source. However, other studies demonstrate efficient signal propagation, such as the climate signals recorded in river flood deposits (Toonen et al, ), or the tectonic uplift signal of the Himalayas recorded in the Bengal fan (Blum et al, ) despite that the Brahmaputra system retains a large percentage (70%) of sediments in the upstream part of the river (Goswami, ). This apparent discrepancy results from using different attributes to detect the signal.…”

Section: Discussionmentioning

confidence: 99%

Applying Information Theory and Bayesian Inference to Paleoenvironmental Interpretation

Plink‐Björklund

2019

Geophysical Research Letters

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Gathering and analyzing data in the most unbiased and reproducible fashion is crucial for successful scientific research. However, scientists are influenced by prior experiences and tend to introduce biases in data interpretation when solutions are nonunique. In Earth science, a key task is the reconstruction of paleoenvironmental conditions, which relies on measurable changes in certain attributes of the resultant landscapes or the sedimentary record. The attributes in use commonly have multiple explanations, which may result in biased interpretation. To mitigate the problem, we propose a general conceptual framework for linking the observed attribute changes to their possible causes based on Shannon's information theory. This framework further serves as a hypothesis generator. We then present a rigorous procedure for paleoenvironmental interpretation based on the multiple-hypotheses method and Bayesian inference. Application examples illustrate the benefits of this procedure in paleoenvironmental reconstructions and in understanding environmental signal propagation through sediment routing systems. Plain Language Summary Sedimentary records and landscapes are an important archive of ourplanet's past environmental conditions. Understanding such conditions is important as it can provide us with perspectives of Earth's evolution far beyond historical time scales and facilitate our prediction of future conditions. However, we are faced with the challenge of nonunique solutions since most observed landscape or sedimentary record changes have more than one possible explanation. To tackle the problem, we propose a model that links observed changes to their possible causes based on information theory. We further suggest a procedure for paleoenvironmental condition interpretation based on the multiplehypotheses method and Bayesian inference, which are proven effective ways to reduce human bias in data interpretation. Our study is an important step toward more quantitative, more reproducible, and less biased interpretation practice.

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Events, episodes, and phases: Signal from noise in flood-sediment archives

Cited by 34 publications

References 36 publications

Sediment Storage Partitioning in Alluvial Stratigraphy: The Influence of Discharge Variability

Sediment Storage Partitioning in Alluvial Stratigraphy: The Influence of Discharge Variability

Storm-generated Holocene and historical floods in the Manawatu River, New Zealand

Applying Information Theory and Bayesian Inference to Paleoenvironmental Interpretation

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