Autogenic delta progradation during sea-level rise within incised valleys

Guérit, Laure; Foreman, Brady Z.; Chen, C.; Paola, Chris; Castelltort, Sébastien

doi:10.1130/g47976.1

Cited by 7 publications

(13 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this work, we provide evidence that an allogenic sea level forcing influences both surface processes and subsurface form. This finding is consistent with prior studies on the subject, which showed that steady SLR (e.g., Feng et al., 2019; Finotello et al., 2019; Guerit et al., 2021; Liang, Van Dyk, & Passalacqua, 2016; Martin, Sheets, et al., 2009) and base level cycles (e.g., Hajek et al., 2014; Kim et al., 2006; Koss et al., 1994; van Heijst & Postmal, 2001) impact both surface processes and the resulting stratigraphy. Uniquely, here, we focus on SLR acceleration by testing the impact that different future sea level trajectories may have on deltaic landscapes.…”

Section: Discussionsupporting

confidence: 93%

Modeling the Dynamic Response of River Deltas to Sea‐Level Rise Acceleration

Hariharan

Passalacqua

et al. 2022

JGR Earth Surface

View full text Add to dashboard Cite

Climate change is raising sea levels across the globe. On river deltas, sea‐level rise (SLR) may result in land loss, saline intrusion into groundwater aquifers, and other problems that adversely impact coastal communities. There is significant uncertainty surrounding future SLR trajectories and magnitudes, even over decadal timescales. Given this uncertainty, numerical modeling is needed to explore how different SLR projections may impact river delta evolution. In this work, we apply the pyDeltaRCM numerical model to simulate 350 years of deltaic evolution under three different SLR trajectories: steady rise, an abrupt change in SLR rate, and a gradual acceleration of SLR. For each SLR trajectory, we test a set of six final SLR magnitudes between 5 and 40 mm/yr, in addition to control runs with no SLR. We find that both surface channel dynamics as well as aspects of the subsurface change in response to higher rates of SLR, even over centennial timescales. In particular, increased channel mobility due to SLR corresponds to higher sand connectivity in the subsurface. Both the trajectory and magnitude of SLR change influence the evolution of the delta surface, which in turn modifies the structure of the subsurface. We identify correlations between surface and subsurface properties, and find that inferences of subsurface structure from the current surface configuration should be limited to time spans over which the sea level forcing is approximately steady. As a result, this work improves our ability to predict future delta evolution and subsurface connectivity as sea levels continue to rise.

show abstract

Section: Discussionsupporting

confidence: 93%

Modeling the Dynamic Response of River Deltas to Sea‐Level Rise Acceleration

Hariharan

Passalacqua

et al. 2022

JGR Earth Surface

View full text Add to dashboard Cite

show abstract

“…So, both deltas migrate towards their respective sediment sources, which are at opposite ends of the estuary. Such retreating deltas are also observed in experimental studies of fluvial deltas with sealevel rise (Guerit et al, 2021;Muto & Steel, 2001). There, the back-stepping of delta lobes is attributed to avulsions instead of allogenic changes in sediment supply or accommodation creation.…”

Section: Flood-tidal Delta Aggradation and Retreatmentioning

confidence: 66%

The effect of sea‐level rise on estuary filling in scaled landscape experiments

Weisscher,

Adema,

Rossius

et al. 2023

The Depositional Record

View full text Add to dashboard Cite

Abstact When sea‐level rise slowed down in the middle Holocene, fluvial and coastal sediments filled the newly created accommodation, whilst others remained largely unfilled because of limited sediment supply. In view of current and future rapid sea‐level rise, the question arises how estuarine systems will adapt and whether the land‐level rise may keep up. Besides geological data and conceptual models of large‐scale and long‐term estuary filling, little is known about the filling process during sea‐level rise on the decadal‐to‐centennial time scale that is relevant for society. This study focusses on how sea‐level rise affects the morphological and hydrodynamic development of filling estuaries. To this end, scaled laboratory experiments were conducted in a tilting flume facility that creates bidirectional tidal currents and develops entire estuaries. A net importing estuary with sand, mud and vegetation was formed that was subjected to linear sea‐level rise. Findings show less of the imported sand was deposited landward following sea‐level rise than in an experiment without sea‐level rise. The bay‐head delta and the flood‐tidal delta retained nearly enough sediment to keep up with sea‐level rise, whilst the tidal embayment in between drowned except for the highest vegetated bars. Sea‐level rise also reduced vegetation survival and sprouting potential, as prolonged inundation increased mortality, negating the potential eco‐engineering effect. This resulted in lower vegetation coverage with sea‐level rise than under constant sea level. These findings suggest that sea‐level rise may cause natural systems to drown even if nearly sufficient sediment is available to fill the newly created accommodation, particularly in areas further away from the fluvial and marine sediment sources. Finally, depending on the sea‐level rise rate, the flood‐tidal delta may show back‐stepping like fluvial deltas, but in the reverse direction towards the sea.

show abstract

“…For a valley that deepens and widens in the seaward direction (Fig. 1E), the model is the same as that presented in Guerit et al (2020). Hence, it is only briefly summarized here.…”

Section: Shoreline Migration Patterns For Complex Valley Geometriesmentioning

confidence: 99%

“…During stage 3, with a further increase in the sea level, A decreases gradually to the point where A is smaller than S, which induces the resumption of progradation, albeit in the overall context of sea-level rise. This condition at stage 3 is termed 'auto-advance' by Guerit et al (2020).…”

Section: Shoreline Migration Patterns For Complex Valley Geometriesmentioning

confidence: 99%

“…Only a relatively small number of studies have instead been undertaken to investigate the role of autogenic processes on the stratigraphic architecture of IVFs, primarily with a focus on the effect of the antecedent topography of the underlying incised valley (e.g. Rodriguez et al ., 2005; Simms & Rodriguez, 2014, 2015; Sahoo & Gani, 2016; Guerit et al ., 2020).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Autogenic evolution of valley‐confined deltas during sea‐level rise: Insights from numerical and physical modelling

Wang,

Kim,

Colombera

et al. 2024

Sedimentology

View full text Add to dashboard Cite

Nearshore incised valleys are important conduits for the transport of sediment, nutrients, pollutants and organic carbon from the continents to the sea. Therefore, it is essential to understand the autogenic evolution of deltas confined within incised valleys and how such evolution is affected by relative sea‐level rise. To date, limited research has focused on how deltas constrained by incised valleys or other forms of antecedent topography respond to rising sea level. An existing theory of autostratigraphy envisages scenarios in which two‐dimensional or unconfined three‐dimensional fan deltas can experience three evolutionary stages under constant rates of relative sea‐level rise and sediment supply: progradation, autoretreat and post‐autobreak transgression. In this work, an integrated study of geometric numerical models and physical experiments is undertaken to investigate autostratigraphic delta evolution for a variety of incised‐valley geometries, under conditions of constant rates of relative sea‐level rise and sediment supply. Results indicate that interplays of antecedent topography (valley geometries) and sediment mass balance expressed in resultant deltaic geometries can result in autogenic changes in shoreline dynamics and river avulsion frequency on deltas. The following primary findings arise. (i) Compared to valleys with rectangular and trapezoidal cross‐sectional profiles, valleys with triangular cross‐sections tend to contain deltas that experience faster rates of progradation, autoretreat and post‐autobreak transgression under rising sea level, and exhibit a more prominent convex‐seaward shoreline trajectory. (ii) The shoreline trajectory is also related to delta topset geometry, becoming more convex‐seaward under decreasing topset slopes. (iii) River avulsion frequency on deltas with rising sea level varies markedly across valleys with different geometries, even under the same rate of relative sea‐level rise; this is attributed to the difference in temporal evolution of shoreline migration for different valley geometries and the resultant difference in the delta topset aggradation. This study highlights complexities in responses of sedimentary systems under the confinement of different topographic configurations that have hitherto largely been overlooked in sequence‐stratigraphic models. The findings provide insight into future shoreline behaviour and river avulsion hazard on confined deltas, and for decoding the stratigraphic record.

show abstract

Autogenic delta progradation during sea-level rise within incised valleys

Cited by 7 publications

References 30 publications

Modeling the Dynamic Response of River Deltas to Sea‐Level Rise Acceleration

Modeling the Dynamic Response of River Deltas to Sea‐Level Rise Acceleration

The effect of sea‐level rise on estuary filling in scaled landscape experiments

Autogenic evolution of valley‐confined deltas during sea‐level rise: Insights from numerical and physical modelling

Contact Info

Product

Resources

About