Abstract
Abstract. The extensive loss of land elevation and the consequent exposure to flood hazards are seriously threatening the long-term survival of the Mississippi Delta. Shallow compaction of the top soil is one of the major components contributing to the relative sea level rise. In the last decades, more subsidence measurements have become available and recent studies demonstrate that compaction of Holocene strata is dominant. Here we propose a novel application aimed at modeling the present-day shallow compaction due to consolidation processes in the top soil. Soil compaction is properly computed and accounts for the large soil grain motion and the delayed dissipation of pore-water overpressure. The grain motion is described by means of a Lagrangian approach with an adaptive mesh where the grid nodes follows the accretion/compaction processes. Model calibration is obtained from stratigraphic and geochrology information collected at the Myrtle Grove Subsidence Superstation, where a nearly 40 m-deep sediment core that penetrates the entire Holocene succession allows testing model results over long (millennial) timescales. Model validation with available observations from rod surface-elevation table – marker horizon (RSET-MH) data enables the model to predict future scenarios.
Highlights
High rates of land subsidence are seriously threatening the long-term survival of the Mississippi Delta
vertical accretion (VA) of 12.5 mm yr−1 are obtained from records collected at site 276 of the Coastwide Reference Monitoring System (CRMS) database as an average value over the time period 2008–2017 CE
Only consolidation process is considered here, in peat formations other processes may play a role in vertical dynamics of surface change, such as those related to the loss of organic matter due to peat oxidation (Rao et al, 2016)
Summary
High rates of land subsidence are seriously threatening the long-term survival of the Mississippi Delta. We propose a novel application aimed at modeling the present-day shallow compaction due to consolidation processes in the Mississippi delta. The model properly computes and accounts for large soil grain motion and the delayed dissipation of porewater overpressure (Zoccarato and Teatini, 2017). This approach is suitable for applications in coastal environments where high rates of shallow compaction requires the adoption of a large soil deformation model (Zoccarato et al, 2018). A validation with available observations from rod surface-elevation table – marker horizon (RSET-MH) data (Jankowski et al, 2017) allows to predict future scenarios. C. Zoccarato et al.: A shallow compaction model for Holocene Mississippi Delta sediments of subsidence.
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