2-D SAR Interferometry for Assessing Ground Deformation of A Reclaimed Area in Lanzhou， China

Land reclamation in mountainous terrains strikingly alters original topography， landform， and hydrology， which could cause serious ground deformation， defined as the gradual or abrupt change of the Earth’s surface caused by natural or human-induced factors and increasing slope instability. Relying on Interferometric Synthetic Aperture Radar (InSAR) technology， a remote sensing technology that measures and monitors ground surface deformation with millimeter-level precision， previous studies have documented the patterns and magnitudes of subsequent deformation after reclamation of the land. However， the impact of initial topography on the patterns of ground deformation is poorly understood. To address this gap， the main objective of this study is to evaluate how initial topographic features influence ground deformation patterns following land reclamation. To assess the impact of reclaimed mountain areas， we integrate the multitemporal ascending and descending InSAR during 2015-2020， and map the ground deformation in a loess land reclamation in Lanzhou， China. Our results reveal pronounced ground deformation velocity of up to 5 cm/a along both ascending and descending tracks within the reclaimed area. The differences in deformation magnitudes between the ascending and descending tracks indicate that the deformation is not entirely vertical. The resolving 2-D ground deformation illustrates that the dominated deformation after land reclamation is essentially vertical and primarily controlled by the thickness of fill or excavated deposits. Additionally， noticeable non-vertical deformation was observed， which is largely determined by the initial topography prior to excavation. To interpret these observations， we proposed a "Three Facets and One Body" model， comprising high cut slopes， high fill slopes， and interface zones， with the one body representing the cumulative volume of fill deposits， providing a framework for understanding the key drivers of ground deformation. These findings emphasized the importance of accounting for both vertical and non-vertical deformation components to more accurately assess slope instability risks in land reclamation projects， especially in mountainous terrains.