Monitoring Landslide Processes by Means of L-Band Radar Interferometric Observations: Using the Example of the Bureya River Bank Caving

Abstract

The possibilities of interferometric surveying using L-band PALSAR-1 and PALSAR-2 space radars on the ALOS-1 and ALOS-2 satellites for studying landslide processes are analyzed using the example of a catastrophic caving of ~18.5 million m3 on the Bureya River in December 2018. The motions of the landslide surface are revealed and their integral amplitude is estimated at time intervals of up to 2 years. It is found that summer images are less informative due to a dramatic loss of coherence due to heavy rainfall; almost all winter pairs of images taken at low negative temperatures have high coherence due to the stability of the dielectric properties of wood vegetation and underlying soils. Based on the analysis of the dynamics of the development of the landslide process over a 10-year time interval, it is shown that soil displacements along the slope were small in 2006–2010 (1.6–1.9 cm/month); in 2015–2016, the displacements increased significantly (4.7–4.9 cm/month), and the maximum measured velocity of displacements was reached in the summer of 2016 (10.7 cm/month). It has been suggested that intensification of the landslide process occurred at the time the filling of the reservoir basin was completed in 2006–2009; the process was triggered by both the initial rise and seasonal fluctuations in water levels.