Data-driven 3D modelling of long-term Holocene delta evolution and sediment compac
tion: The Mekong Delta
S. Baldan, R. Xotta, C. Zoccarato, P. Teatini
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
P. S. J. Minderhoud
Soil Geography and Landscape group,
Wageningen University & Research,
Wageningen, The Netherlands
ABSTRACT
The Vietnamese Mekong River Delta (VMD) is one of the largest and lowest elevated
deltas on Earth, shaped over the past thousands of years following delta
progradation and sediment deposition. The geologically young delta sediments have high
porosity and compressibility, resulting in high natural sediment consolidation (also
known as autocompaction). Autocompaction is a natural intrinsic process that governs
the spatio-temporal morphological evolution and shallow compaction (i.e., land
subsidence) in a delta. As a delta aggrades and progrades, the weight of accumulated
sediments increases the effective stress experienced by underlying sediments, driving
internal shallow compaction processes. Compaction of shallow sediments considerably
contributes to land subsidence in the VMD, influencing the morphology and
elevation of the delta plain and increasing the deltas exposure to natural hazards like
flooding and relative sea-level rise. In this study, we introduce a novel methodology
to quantify sediment accumulation and autocompaction while taking into account
the depositional history and heterogeneous nature of subsurface sediments in deltas
like the VMD. We derived the depositional history, spatial heterogeneity and palaeo-sedimentation
rates by combining extensive datasets with lithological borelogs, sediment
datings and geomechanical characterization of the delta's most representative
lithologies. To simulate the spatio-temporal formation and evolution of the delta over
the last 4000 years, we employ the NATSUB3D finite element model to simulate
sediment deposition and consolidation over time using an adaptive three-dimensional
mesh. The resulting 3D hydro-stratigraphical and geomechanical
characterization provides unique insights on past Holocene spatio-temporal evolution of
the VMD and current autocompaction dynamics. The model enables the prediction
of shallow compaction rates under future sediment deposition and can facilitate
process-based quantification of delta elevation evolution under natural and
human-engineered sedimentation. This unlocks new opportunities to evaluate the effectiveness
of nature-based solutions and sediment enhancing strategies aimed to prevent
elevation loss and combat relative sea-level rise in the Mekong delta and similar lowly
elevated coastal-deltaic landforms elsewhere.
