Abstract:
SAR data constrain deformation of the Portuguese Bend landslide in space and
time, and its movement is found to correlate with seasonal rainfall. Traditional InSAR
methods estimate an average downslope displacement rate of 1.01 à ± 0.44 m/yr during the
summer months. Interferograms show a consistent loss in phase coherence over the
landslide for epochs greater than six months, especially in the winter. Interferograms
become incoherent as a result of large displacement, and incoherence is used to map the
spatial extent of the slide through time. The displacement rate increases several weeks
after the beginning of the rainy season as rainwater percolating into the slide elevates
pore pressure. SAR data processed using the permanent scatterer technique are partially
successful on the rapidly moving landslide. Scatterers are identified on the landslide, but
rates are underpredicted due to unwrapping uncertainty. A model based on rainfall-initiated
landslides constrains diffusivity using InSAR observations.