Modeling peatland hydrology and related elastic deformation
M. Camporese
Dept. Hydraulic, Maritime, Environmental, and Geotechnical Engineering,
University of Padova, Padova, Italy
M. Putti, P. Teatini,
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
P. Salandin
Institute of Hydraulics and Road Infrastructures, Polytechnic University
of Marche, Ancona, Italy
ABSTRACT
Reversible surface displacements occur at time scales of hours in peatlands
that are subject to drying and rewetting cycles. This phenomenon is related
to the long term subsidence caused by biological oxidation of the organic
matter under aerobic conditions that peat drainage for agricultural purposes
induces in temperate regions. Modeling land subsidence of peatland surface
requires, at a preliminary stage, the separation between the elastic deformation
related to water table and soil moisture changes and the irreversible sinking
of land due to peat oxidation. In this paper peat hydrology is modeled together
with soil deformation in a one-dimensional column subject to soil moisture
fluctuations due to precipitation, evapotranspiration, and drainage. The test
case is representative of a field test bog located south of Venice (Italy),
where hydrologic and displacement data have been continuously recorded since
November 2001. A linear, one-dimensional pattern of elastic peat swelling/shrinkage
relating the soil deformation to the gravimetric water content is implemented
by coupling a variably saturated finite element flow model to a soil volume
change equation. In this study the oxidation of peat is ignored, the time scale
of water table fluctuations being much less than that of the long term subsidence
process. The comparison of the numerical results with the large dataset
available from the Venice monitoring site allows for the calibration of the
hydraulic and mechanical parameters of the soil and assesses the validity of
the proposed deformation model.
