Exploring the role of organic matter accumulation on delta evolution

Lorenzo‐Trueba, Jorge; Voller, V. R.; Paola, Chris; Twilley, Robert R.; Bevington, A.

doi:10.1029/2012jf002339

Cited by 38 publications

(27 citation statements)

References 62 publications

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“…The processes we have discussed thus far control the deposition rates of mineral (nonorganic) riverine sediment. However, organic matter is often a significant fraction of the composition of a river delta; it is anywhere from 10% to 40% by weight for the Mississippi Delta coastal marshes, for example [ Lorenzo‐Trueba et al ., ; Khan et al ., ]. Biological drivers of sediment accumulation are beyond the scope of this review.…”

Section: Implications For Delta Restoration and Erosion Mitigation Stmentioning

confidence: 98%

Dynamics of river mouth deposits

Fagherazzi

Edmonds

Nardin

et al. 2015

Reviews of Geophysics

145

104

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Bars and subaqueous levees often form at river mouths due to high sediment availability. Once these deposits emerge and develop into islands, they become important elements of the coastal landscape, hosting rich ecosystems. Sea level rise and sediment starvation are jeopardizing these landforms, motivating a thorough analysis of the mechanisms responsible for their formation and evolution. Here we present recent studies on the dynamics of mouth bars and subaqueous levees. The review encompasses both hydrodynamic and morphological results. We first analyze the hydrodynamics of the water jet exiting a river mouth. We then show how this dynamics coupled to sediment transport leads to the formation of mouth bars and levees. Specifically, we discuss the role of sediment eddy diffusivity and potential vorticity on sediment redistribution and related deposits. The effect of waves, tides, sediment characteristics, and vegetation on river mouth deposits is included in our analysis, thus accounting for the inherent complexity of the coastal environment where these landforms are common. Based on the results presented herein, we discuss in detail how river mouth deposits can be used to build new land or restore deltaic shorelines threatened by erosion.

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Section: Implications For Delta Restoration and Erosion Mitigation Stmentioning

confidence: 98%

Dynamics of river mouth deposits

Fagherazzi

Edmonds

Nardin

et al. 2015

Reviews of Geophysics

145

104

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“…Many of these models include sediment particle size and topography (Burpee et al, ; Edmonds & Slingerland, ). However, to date, there are few modeling studies that include OM dynamics (Lorenzo‐Trueba et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Many of these models include sediment particle size and topography (Burpee et al, 2015;Edmonds & Slingerland, 2009). However, to date, there are few modeling studies that include OM dynamics (Lorenzo-Trueba et al, 2012). Shields et al (2017) quantified the mass of carbon stored in WLD based on the relationship between carbon stock and elevation.…”

Section: Connecting Om Dynamics With Environmental Driversmentioning

confidence: 99%

Factors Controlling Storage, Sources, and Diagenetic State of Organic Carbon in a Prograding Subaerial Delta: Wax Lake Delta, Louisiana

et al. 2019

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Wax Lake Delta, southern Louisiana, is a coastal delta that formed following the dredging of a river channel in 1941 and is a field model for investigating the geomorphology, ecology, carbon dynamics, and carbon storage capacity in young prograding deltas. However, it is unknown how the transition from subaqueous to subaerial sediments affects the sources and quality of the sequestered carbon. We investigated these variations within the sediments of Wax Lake Delta using amino acid, lignin, and stable carbon isotope compositions of the organic matter (OM). A principal component analysis of these proxies highlighted variability in organic carbon (OC) composition with changes in elevation. The transition from subaqueous to subaerial sediments at 0‐cm mean lower low water is an important component of the OM composition. In addition to the changes observed for OM source and quality, the OC loadings (OC/SA; mg C/m2) also increase as the delta aggrades and accumulates sediments with loadings typical of delta topsets and mobile mud banks (OC/SA < 0.4) to riverine sediments (0.5 < OC/SA < 1) and eventually to highly productive regions (OC/SA > 1). Linking this multiproxy approach with environmental variables such as elevation provides a path for incorporating OM dynamics into geomorphic models.

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“…A second feedback is that a significant fraction of sediment accumulation can be organic, which can make up 11–15% of the deposit for some large river deltas (

r_{0} \sim 0.12

–0.18 Gouw, ; Holmquist et al, ). However, such organic deposition is understood to occur only when a delta is starved of mineral sediment but not fully inundated and abandoned (Bohacs & Suter, ; Kosters et al, ; Lorenzo‐Trueba et al, ). Third, the trapping efficiency (

k

) of mineral sediment varies significantly depending on the delta morphology and characteristics of coastal plain (Nardin & Edmonds, ; Nardin et al, ; Nienhuis et al, ) and material properties of the unchannelized delta deposits (Straub et al, ).…”

Section: Grand Challengesmentioning

confidence: 99%

Resilience of River Deltas in the Anthropocene

et al. 2020

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At a global scale, delta morphologies are subject to rapid change as a result of direct and indirect effects of human activity. This jeopardizes the ecosystem services of deltas, including protection against flood hazards, facilitation of navigation, and biodiversity. Direct manifestations of delta morphological instability include river bank failure, which may lead to avulsion, persistent channel incision or aggregation, and a change of the sedimentary regime to hyperturbid conditions. Notwithstanding the in‐depth knowledge developed over the past decades about those topics, existing understanding is fragmented, and the predictive capacity of morphodynamic models is limited. The advancement of potential resilience analysis tools may proceed from improved models, continuous observations, and the application of novel analysis techniques. Progress will benefit from synergy between approaches. Empirical and numerical models are built using field observations, and, in turn, model simulations can inform observationists about where to measure. Information theory offers a systematic approach to test the realism of alternative model concepts. Once the key mechanism responsible for a morphodynamic instability phenomenon is understood, concepts from dynamic system theory can be employed to develop early warning indicators. In the development of reliable tools to design resilient deltas, one of the first challenges is to close the sediment balance at multiple scales, such that morphodynamic model predictions match with fully independent measurements. Such a high ambition level is rarely adopted and is urgently needed to address the ongoing global changes causing sea level rise and reduced sediment input by reservoir building.

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Exploring the role of organic matter accumulation on delta evolution

Cited by 38 publications

References 62 publications

Dynamics of river mouth deposits

Dynamics of river mouth deposits

Factors Controlling Storage, Sources, and Diagenetic State of Organic Carbon in a Prograding Subaerial Delta: Wax Lake Delta, Louisiana

Resilience of River Deltas in the Anthropocene

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