Investigating slow-moving shallow soil landslides using Sentinel-1 InSAR data in Gisborne, New Zealand

Abstract

Landslides are widespread geomorphological features on the North Island of New Zealand, where they represent one of the primary landscape-forming processes. This study focuses on the steepland terrain surrounding Gisborne, a city located on the east coast of the North Island, at the Hikurangi subduction margin. This terrain consists of young, weak, sedimentary rocks and soils; the most common modes of slope failures are soil creep, slides and flows in shallow, clay-rich soil and regolith, triggered by heavy rainfall. Based on observational data from Sentinel-1 imagery, this study leverages results from interferometric synthetic aperture radar (InSAR) processing to reveal the distribution of deformation across Gisborne’s steepland periphery from January 2016 to December 2021. Velocities in the line of sight were obtained from the stack of interferograms and projected along the direction of maximum slope, to extract the true displacement on the slopes. The ascending and descending data sets were combined to reveal the vertical and horizontal components of the deformation. The results were combined with a regional LiDAR data set, aerial imagery and field observations to delineate areas of slope deformation. Finally, slope deformation time series data was compared with rainfall records to identify seasonal changes, due to shrinking and swelling of expansive soils. Although the InSAR displacement data contains some noise, results could be used to identify 132 unstable slopes within the study area, caused by soil creep and earthflows. Also, the shrink-swell of expansive soils causes a seasonal pattern of displacements, which varied by 10–20 mm/year between Austral winter and summer, strongly correlated to rainfall.

Active Deformation Areas of Potential Landslide Mapping with a Generalized Convolutional Neural Network

“…Landslide is a geological phenomenon characterized by the downward movement of soil or rock mass on a slope. This movement occurs due to various factors, including rainfall, river erosion, groundwater activity, earthquakes, and human-induced slope cutting [20,[30][31][32]. At present, researchers comprehensively detect landslides using the associated characteristics describing landslides, such as the spectral features, other morphological and appearance characteristics from remote sensing images, and lithological, hydrological, and geological factors.…”

Instrumental Monitoring of a Slow-Moving Landslide in Piedmont (Northwest Italy) for the Definition of Rainfall Thresholds

“…In addition to contact sensors for the quantification of displacement, in recent decades, the utility of Interferometric SAR (InSAR) to identify, map and monitor landslides has been demonstrated [ 25 ] and, as a consequence, InSAR has become consolidated in the field of geotechnics as a tool for the study of landslides. It is largely used for the study of landslide’s reactivation [ 26 ], for the characterization of precursors and triggering factors [ 27 ], for the comparison between landslide behaviour and rainfall characteristics [ 28 ] and for landslide inventory purposes [ 29 ], among others (for a complete review, see [ 30 ]).…”

Mass movement evaluation in deformed clastic rock with InSAR technique

“…Arca et al (2018) used the multicriteria decision analysis method to create an LSM for the Kozlu mining area in Zonguldak (N Türkiye). The SBAS method was used to extract the deformation distribution around the steep terrain of Gisborne in New Zealand from Sentinel‐1 images between 2016 and 2021 by Cook et al (2023). With the SBAS results, a regional LiDAR dataset was merged with aerial photographs and field observations to identify areas of slope deformation.…”