Sedimentary signals of fluvial discharge variability under tide and wave influence: Miocene examples in NW Borneo

2021 ◽  
Author(s):  
Daniel Collins ◽  
Howard Johnson
Keyword(s):  
River Discharge ◽  
Tidal Channel ◽  
Flood Wave ◽  
Wave Processes ◽  
Stratigraphic Architecture ◽  
Modern Analogue ◽  
River Flood ◽  
Sedimentary Dynamics ◽  
Tidal Variations ◽  
Tidal Processes

<p>The interaction of river and marine processes in the fluvial to marine transition zone (FMTZ) fundamentally impacts sedimentary dynamics and deposition. Heterolithics are important facies within ancient and modern FMTZs but the preserved signal of river flood, wave and tidal variations in heterolithics remains uncertain. This study integrates facies and ichnofacies characteristics of heterolithics in the Lambir Formation (Baram Delta Province, NW Borneo), with information of larger-scale stratigraphic architecture and modern analogue information, to interpret the preserved record of river flood deposits under the influence of tides and waves in an ancient FMTZ. Within the FMTZ of distributary channels, interpreted proximal–distal sedimentological and stratigraphic trends suggest: (1) a proximal fluvial-dominated, tide-influenced subzone; (2) a distal fluvial- to wave-dominated subzone; and (3) a conspicuously absent tide-dominated subzone. During coupled storm and river floods, fluvial processes dominated the FMTZ along major and minor distributary channels and channel mouths, causing significant overprinting of preceding interflood deposits and deposition of thicker, sandier event beds. Intervening interflood deposits are muddier, with increased bioturbation, and may variably preserve sedimentary indicators of tide and wave processes. Despite interpreted fluvial–tidal channel units and mangrove influence implying tidal processes, there is a paucity of unequivocal tidal indicators (e.g. cyclical heterolithic layering). This suggests that process preservation in the FMTZ preserved in the Lambir Formation primarily records episodic (flashy) river discharge, river flood and storm overprinting of tidal processes, and possible backwater dynamics. </p>

River discharge variability in the rock record? Disentangling the relative role of flow variability and morphodynamic hierarchies on bedform preservation

2021 ◽  
Author(s):  
Sinead Lyster ◽  
Alexander Whittaker ◽  
Elizabeth Hajek ◽  
Vamsi Ganti ◽  
Peter Allison
Keyword(s):  
River Discharge ◽  
Quantitative Information ◽  
Relative Role ◽  
Flow Conditions ◽  
Fluvial Systems ◽  
Flow Variability ◽  
Stratigraphic Architecture ◽  
Coefficients Of Variation ◽  
Rock Record

<p>River discharge variability is a fundamental control on fluvial morphodynamics and, in principle, stratigraphic architecture. The ability to quantitatively constrain discharge variability from fluvial stratigraphy would newly enable us to reconstruct instantaneous or interannual responses of rivers to climatic perturbation in the geologic past. However, the extent to which we can extract quantitative information about discharge variability from fluvial stratigraphy is currently unknown. Recent experimental work indicates that preserved cross-set geometries can potentially be used to inform formative flow conditions and durations. However, to date, this has not been tested on field examples of ancient fluvial systems. Here we use detailed measurements of cross-sets to assess bedform kinematics and formative flow conditions in fluvial strata of three Late Cretaceous geologic formations: the Blackhawk Formation, Castlegate Sandstone, and Ferron Sandstone, which crop out in central Utah, USA.</p><p>Unanimously low coefficients of variation (<em>CV</em>) in preserved cross-set heights of 0.25–0.5 are consistent with the hypothesis that <em>CV</em><<0.88 arises from preservation of bedforms in disequilibrium conditions, which typically occurs during rapid flood recession in a “flashy” flood hydrograph. Bedform preservation in disequilibrium conditions requires that formative flow durations are shorter than bedform turnover timescales. We reconstruct median turnover timescales of 2–3 days, with a 10–90 percentile range of ~1–10 days, which implies that formative flow durations were of order hours to a few days. These durations are consistent with storm-related flood durations in perennial discharge regimes, as opposed to the more sustained flood durations that are typical of subtropical/monsoonal climate regimes. However, it is also possible that this same <em>CV</em> signature (<em>CV</em><<0.88) can be achieved simply by the presence of morphodynamic hierarchies, e.g. concurrently migrating bedforms and bars. We explore whether it is possible to disentangle the relative role of formative flow conditions and morphodynamic hierarchies on bedform preservation using our field data, models of flood stratigraphy, and estimates of bedform preservation ratios. Moreover, we identify future steps that will further our ability to quantitatively extract formative flow variability and, ultimately, discharge variability from the rock record. </p>

scholarly journals Extreme Coastal Water Levels Exacerbate Fluvial Flood Hazards in Northwestern Europe

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Poulomi Ganguli ◽  
Bruno Merz
Keyword(s):  
Coastal Water ◽  
River Discharge ◽  
Storm Surges ◽  
Water Levels ◽  
Peak Discharge ◽  
Flood Hazards ◽  
Coastal Zones ◽  
Winter Storm ◽  
Return Levels ◽  
River Flood

Abstract Compound flooding, such as the co-occurrence of fluvial floods and extreme coastal water levels (CWL), may lead to significant impacts in densely-populated Low Elevation Coastal Zones. They may overstrain disaster management owing to the co-occurrence of inundation from rivers and the sea. Recent studies are limited by analyzing joint dependence between river discharge and either CWL or storm surges, and little is known about return levels of compound flooding, accounting for the covariance between drivers. Here, we assess the compound flood severity and identify hotspots for northwestern Europe during 1970–2014, using a newly developed Compound Hazard Ratio (CHR) that compares the severity of compound flooding associated with extreme CWL with the unconditional T-year fluvial peak discharge. We show that extreme CWL and stronger storms greatly amplify fluvial flood hazards. Our results, based on frequency analyses of observational records during 2013/2014’s winter storm Xaver, reveal that the river discharge of the 50-year compound flood is up to 70% larger, conditioned on the occurrence of extreme CWL, than that of the at-site peak discharge. For this event, nearly half of the stream gauges show increased flood hazards, demonstrating the importance of including the compounding effect of extreme CWL in river flood risk management.

Tidal sedimentary dynamics of the Early Pleistocene Messina Strait (Calabria, southern Italy) based on its modern analogue

2020 ◽  
Vol 12 (2.4) ◽  
pp. 1-45
Author(s):  
Sergio G. Longhitano ◽  
Domenico Chiarella ◽  
Marcello Gugliotta ◽  
Pascal Barrier ◽  
Dario Ventra ◽  
...  
Keyword(s):  
Southern Italy ◽  
Early Pleistocene ◽  
Modern Analogue ◽  
Sedimentary Dynamics ◽  
Messina Strait

Sources and routing of the Amazon River Flood Wave

1989 ◽  
Vol 3 (3) ◽  
pp. 191-204 ◽  
Author(s):  
Jeffrey E. Richey ◽  
Leal A. K. Mertes ◽  
Thomas Dunne ◽  
Reynaldo L. Victoria ◽  
Bruce R. Forsberg ◽  
...  
Keyword(s):  
Amazon River ◽  
Flood Wave ◽  
River Flood

Orbital SAR remote sensing of a river flood wave

1998 ◽  
Vol 19 (7) ◽  
pp. 1439-1445 ◽  
Author(s):  
G. R. Brakenridge ◽  
B. T. Tracy ◽  
J. C. Knox
Keyword(s):  
Remote Sensing ◽  
Flood Wave ◽  
River Flood ◽  
Sar Remote Sensing

scholarly journals Sedimentary Dynamic and Composition of a Tidal Channel in a Tropical Hot Semi-Arid Environment, NE Brazil

2020 ◽  
Vol 43 (4) ◽  
Author(s):  
Ian Cerdeira de Oliveira Souza ◽  
Guilherme Augusto Mendonça Maia ◽  
Narelle Maia de Almeida ◽  
João Capistrano Abreu Neto ◽  
George Satander Sá Freire
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Organic Matter Content ◽  
Matter Content ◽  
Shrimp Farming ◽  
Arid Climate ◽  
Carbonate Content ◽  
Tidal Channel ◽  
Sedimentary Dynamics ◽  
Semi Arid

Tidal channels comprise a peculiar and dynamic environment. This paper aims to recognize the sedimentary distribution and composition of a tidal channel located in a semi-arid climate area in order to understand the sedimentary dynamics of the region. This region has economic and environmental importance considering that several activities are developed in the area such as; salt industry and aquaculture with shrimp farming. The results and discussion presented here on the Barra Grande Port tidal channel are based on 43 superficial samples distributed in the area, in which we analyzed the grain-size distribution and the calcium carbonate and organic matter contents. The data enabled the characterization and compartmentalization of the tidal channel on five sections and the interpretation of the sedimentary dynamics of the area. The sections present an important variation in the composition and selection. The section 1 is located in supratidal zone while sections 02, 03, 04 and 05 are in intertidal zone. The grain-size mean has a tendency to decrease toward the end of the channel as well as the gravel percentage, and the carbonate and organic matter contents. Differently, the mud content and the sorting increase toward the end of the channel and the skewness becomes more positive. In a general way, the carbonate content is high throughout the tidal channel ranging from 20 to 98% while the organic matter content is low ranging from 0 to 3%. This sedimentary distribution occurs due to the development of a hydraulic dam on section 3, causing a morphological growth of this sand bar, which acts as a natural hydraulic dam, hampering the access of the tide and consequently reducing the effectiveness of the transport, resulting in the deposition of fine sediments in the sheltered areas of the channel (sections 04 and 05). The high temperatures and low rainfall of the tropical hot semi-arid climate allowed the development of carbonate sedimentation as well as the development of anthropic activities such as salt extraction in artificial salt pans which may have influenced the low levels of organic matter.

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