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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union
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Volume 5, issue 3 | Copyright
Earth Surf. Dynam., 5, 387-397, 2017
https://doi.org/10.5194/esurf-5-387-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 12 Jul 2017

Research article | 12 Jul 2017

Efficient retention of mud drives land building on the Mississippi Delta plain

Christopher R. Esposito1,a,*, Zhixiong Shen2,*, Torbjörn E. Törnqvist1, Jonathan Marshak1, and Christopher White1 Christopher R. Esposito et al.
  • 1Department of Earth and Environmental Sciences, Tulane University, 6823 St. Charles Avenue, New Orleans, Louisiana 70118-5698, USA
  • 2Department of Marine Science, Coastal Carolina University, P.O. Box 261954, Conway, South Carolina 29528, USA
  • anow at: The Water Institute of the Gulf, One American Place, 301 N. Main Street, Suite 2000, Baton Rouge, Louisiana 70825, USA
  • *These authors contributed equally to this work.

Abstract. Many of the world's deltas – home to major population centers – are rapidly degrading due to reduced sediment supply, making these systems less resilient to increasing rates of relative sea-level rise. The Mississippi Delta faces some of the highest rates of wetland loss in the world. As a result, multibillion dollar plans for coastal restoration by means of river diversions are currently nearing implementation. River diversions aim to bring sediment back to the presently sediment-starved delta plain. Within this context, sediment retention efficiency (SRE) is a critical parameter because it dictates the effectiveness of river diversions. Several recent studies have focused on land building along the open coast, showing SREs ranging from 5 to 30%. Here we measure the SRE of a large relict crevasse splay in an inland, vegetated setting that serves as an appropriate model for river diversions. By comparing the mass fraction of sand in the splay deposit to the estimated sand fraction that entered it during its life cycle, we find that this mud-dominated sediment body has an SRE of ≥75%, i.e., dramatically higher than its counterparts on the open coast. Our results show that transport pathways for mud are critical for delta evolution and that SRE is highly variable across a delta. We conclude that sediment diversions located in settings that are currently still vegetated are likely to be the most effective in mitigating land loss and providing long-term sustainability.

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Our work presents a novel method of measuring the capacity of deltaic landforms to trap and retain river-borne sediments, and we demonstrate that sediment retention is closely connected to sedimentary composition. Our results, supported by a unique high-resolution coring dataset in a major crevasse splay, show that finer sediments are a much larger component of the Mississippi Delta than is often acknowledged and that their abundance indicates exceptionally high rates of sediment retention.
Our work presents a novel method of measuring the capacity of deltaic landforms to trap and...
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