In-situ loading experiments reveal how the subsurface affects coastal marsh survival
C. Zoccarato, P. S. J. Minderhoud, P. Zorzan, V. Girardi, P. Simonini, P. Teatini
Dept. of Civile, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
L. Tosi, C. Cavallina, M. Cosma, C. Da Lio, S. Donnici
Institute of Geosciences and Earth Resources, National Research Council, Padova, Italy
A. Bergamasco
Institute of Marine Sciences, National Research Council, Venice, Italy
ABSTRACT
Over the past decades coastal marshes around the world have declined dramatically. Their
deterioration is controlled by scarcity of sediments, erosion and accelerated rise of relative
sea-level. The feedbacks between these processes control marsh evolution and determine
their long-term survivability. Aggradation of a marsh to keep pace with relative sea-level rise
mainly depends on the interplay between sedimentation and autocompaction, but their
interactions are severely understudied. Here we present an in-situ loading experiment applied
in the Venice Lagoon, Italy, to assess long-term autocompaction, with subsurface displace-
ments and pressure monitored during loading cycles, up to ∼ 40 kN applied on a ∼ 4 m2
surface. Two identical experiments carried out in inorganic and organic soil-dominated
marshes provided unique insights on the spatio-temporal subsurface dynamics. The large
differences in behavior and maximum compaction (6 vs 32 mm) underscore the crucial role
of autocompaction and soil heterogeneity when predicting the fate of coastal marshes
worldwide.
