Shallow Deformation in the Netherlands Due to Peat Decomposition,
Measured by Persistent Scatterer Interferometry

M. Caro Cuenca and R. F. Hanssen

The western part of the Netherlands has a typical Dutch landscape with
drained peat meadows in polders below sea level. The area is used in
concert for agriculture, residence, and nature conservation. Large
areas of this region are fen-meadows that consist of wet pasture lands
with drained peat soils alternated by natural and artificial lakes,
ditches and quaking fens. To keep the land suitable for agricultural
use, the peat area has been drained deeper in recent decades. This
drainage has resulted in a subsidence of the soil and as a result the
polders with fen-meadows are now 12 m below sea level. The observation
of subsidence of wetlands is notoriously difficult using conventional
geodetic techniques, due to the absence of fixed benchmarks. Here we
show that analyses from Persistent Scatterer Interferometry (PSI) can
be used to infer subsidence rates of several millimeters per year,
using coherent targets identified in the area. These results are
obtained over the Green Heart, an open area surrounded by a
horseshoe-shaped ring of cities, Randstad Holland. The derived
subsidence rates will be interpreted and related to processes in the
shallow subsurface.