Does Load‐Induced Shallow Subsidence Inhibit Delta Growth?

Chamberlain, E. L.; Shen, Zhixiong; Kim, Wonsuck; Törnqvist, Torbjörn E.; McKinley, Samantha; Anderson, S.

doi:10.1029/2021jf006153

Cited by 12 publications

(13 citation statements)

References 62 publications

(152 reference statements)

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“…We designed the reduced‐complexity modeling approach undertaken in this study to exclusively test the impact of future SLR on river‐dominated delta landscapes. As a result, we did not consider many physical processes such as wind (e.g., Ortiz et al., 2017), waves (e.g., Anthony, 2015), vegetation (e.g., Lauzon & Murray, 2018; Piliouras et al., 2017), tides (e.g., Galloway, 1975; Sassi et al., 2012), subsidence (e.g., Chamberlain et al., 2021; Zoccarato et al., 2018), and variable discharge (e.g., Gao et al., 2019; Miller et al., 2019; Shaw & Mohrig, 2014), although their presence, absence, and relative magnitudes are known to influence delta evolution. However, we do not believe that all of these additional forcings would significantly change the results found here; Van De Lageweg and Slangen (2017) simulated delta evolution over centennial timescales with different forcing and SLR conditions, and found river, tidal, and wave‐dominated deltas all responded similarly to SLR.…”

Section: Discussionmentioning

confidence: 99%

“…Trends of increasing connectivity as the rate of SLR increased in the "abrupt" and "gradual" scenarios, suggest that the shallow subsurface of natural river deltas in the future will become more connected as sea levels rise. The shallow subsurface is also susceptible to subsidence due to compaction (e.g., Keogh et al, 2021;Teatini et al, 2011;Törnqvist et al, 2008;Van Asselen et al, 2011), a process not considered in this work, but one which can impact delta growth and evolution (Chamberlain et al, 2021;Zoccarato et al, 2018).…”

Section: Subsurface Connectivity Of Shallow Deltaic Stratigraphymentioning

confidence: 99%

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

Hariharan

Passalacqua

et al. 2022

JGR Earth Surface

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Subsurface Connectivity Of Shallow Deltaic Stratigraphymentioning

confidence: 99%

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

Hariharan

Passalacqua

et al. 2022

JGR Earth Surface

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“…Notwithstanding the overall modest subsidence rates at the superstation site, this may change in the near future due to the Mid‐Barataria Sediment Diversion that aims to build and maintain deltaic (wet) land in the area surrounding the superstation (Coastal Protection and Restoration Authority of Louisiana, 2017). When implemented, this river diversion will bring a significant increase in clastic sediment, likely accelerating shallow compaction (e.g., Chamberlain et al., 2021). Our data provide a valuable pre‐diversion baseline to assess the impacts of the Mid‐Barataria Sediment Diversion with regard to subsidence.…”

Section: Synthesis and Implicationsmentioning

confidence: 99%

“…While this may not presently be the case at the superstation, it is well documented that Holocene sediment compaction dominates the total present‐day subsidence in most of coastal Louisiana (e.g., Chamberlain et al., 2021; Jankowski et al., 2017; Karegar et al., 2015; Keogh et al., 2021; Meckel et al., 2006; Penland & Ramsey, 1990; Törnqvist et al., 2008). Previously buried (Pleistocene) sediments do not significantly decompact with unloading (Chapman, 1983).…”

Section: Synthesis and Implicationsmentioning

confidence: 99%

Novel Integration of Geodetic and Geologic Methods for High‐Resolution Monitoring of Subsidence in the Mississippi Delta

et al. 2022

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Coastal lowlands and river deltas, which rise less than 10 m above sea level, are particularly vulnerable to the climate-change effects forecast for the 21st century and beyond, including the threat of inundation by accelerating sea-level rise and increases in the severity of tropical storm surges. Most large deltas are receiving insufficient sediment to maintain themselves (Giosan et al., 2014). These threats coincide with a worldwide surge in human population in coastal areas. Coastal population centers include multiple megacities, whose inhabitants exceed 10 million. Many of these coastal megacities are located on river deltas that are also hubs and hot spots for agriculture, fisheries, transportation, and hydrocarbon production. Most deltas are subsiding, in many cases at rates exceeding the rate of sea-level rise (e.g.,

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“…Furthermore, Day et al (2011) found that soil strength is higher in marshes with riverine MM input compared to marshes with high OM content that lack riverine input. However, MM-dominated deltaic muds are also highly compressible (e.g., Fisk et al, 1954;Minderhoud et al, 2018;Zoccarato et al, 2018) and may be at least as compressible as organic-rich sediments in some cases (e.g., Chamberlain et al, 2021).…”

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confidence: 99%

Organic Matter Accretion, Shallow Subsidence, and River Delta Sustainability

et al. 2021

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River deltas serve as critical nodes in the global water-energy-food nexus. They host large and rapidly growing populations (Edmonds et al., 2020) with associated economic assets, and many deltas provide important ecosystem goods and services. Thus, delta sustainability is a critical issue, and it is widely recognized that maintaining deltaic plains in the face of accelerating relative sea-level rise (RSLR) is a major priority that will become increasingly daunting in the future (e.g., Day et al., 2016;Hoitink et al., 2020;Nienhuis et al., 2020). On many deltaic plains, mineral sediment supply has decreased dramatically since the mid-twentieth century, largely due to the construction of dams, artificial levees, and other flood-control infrastructure (e.g., Giosan et al., 2014;Syvitski et al., 2005;Weston, 2014), a trend that is expected to continue in the 21st century (Dunn et al., 2019). In the Yangtze and Mississippi rivers, for example, dams have reduced the suspended sediment concentration by Abstract Globally, mineral sediment supply to deltaic wetlands has generally decreased so these wetlands increasingly rely on accretion of organic matter to keep pace with relative sea-level rise (RSLR). Because organic-rich sediments tend to be more compressible than mineral-dominated sediments, deltaic wetland strata are vulnerable to compaction and drowning. Using an unprecedented data set of almost 3,000 discrete bulk density and organic-matter measurements, we examine organic-rich facies from coastal Louisiana to quantify the thickness lost to compaction and investigate whether sediments are able to maintain sufficient volume for the associated wetlands to keep pace with RSLR. We find that organic content as well as overburden thickness and density (which together determine effective stress) strongly control sediment compaction. Most compaction occurs in the top 1-3 m and within the first 100-500 years after deposition. In settings with thick peat beds, successions up to 14 m thick have been compacted by up to ∼50%. We apply geotechnical modeling to examine the balance between elevation gained from accretion and elevation lost to compaction due to renewed sediment deposition over a 100-year timescale. Wetlands overlying mineral-dominated lithologies may support the weight of deposition and allow net elevation gain. Model results show that reintroduction of sediment to a representative Mississippi Delta wetland site will likely cause another ∼0.35-1.14 m of compaction but leave a net elevation gain of ∼0.01-1.75 m, depending on the sediment delivery rate and stiffness of underlying strata.Plain Language Summary River deltas constitute some of the most valuable but also most vulnerable environments on the planet. Their elevation right above sea level is controlled by a delicate balance between sediment deposition and compaction. If sediment delivery is reduced due to dam construction in the hinterland, for example, sedimentation rates decrease. Continued sediment compaction may prevent deltas from keeping up with sea-...

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Does Load‐Induced Shallow Subsidence Inhibit Delta Growth?

Cited by 12 publications

References 62 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

Novel Integration of Geodetic and Geologic Methods for High‐Resolution Monitoring of Subsidence in the Mississippi Delta

Organic Matter Accretion, Shallow Subsidence, and River Delta Sustainability

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