Characterizing the Topographic Changes and Land Subsidence Associated with the Mountain Excavation and City Construction on the Chinese Loess Plateau

Chuanhao Pu,Qiang Xu,Yanan Jiang,Lina Hao,Jialiang Liu,Kuanyao Zhao,Pinglang Kou,Wanlin Chen

doi:10.3390/rs13081556

Abstract

A mega project, Mountain Excavation and City Construction (MECC), was launched in the hilly and gully region of the Chinese Loess Plateau in 2012, in order to address the shortage of available land and create new flat land for urban construction. However, large-scale land creation and urban expansion significantly alters the local geological environment, leading to severe ground deformation. This study investigated the topographic changes, ground deformation, and their interactions due to the MECC project in the Yan’an New District (YND). First, new surface elevations were generated using ZiYuan-3 (ZY-3) stereo images acquired after the construction in order to map the local topographic changes and the fill thickness associated with the MECC project. Then, the interferometric synthetic aperture radar (InSAR) time series and 32 Sentinel-1A images were used to assess the spatial patterns of the ground deformation in the YND during the postconstruction period (2017–2018). By combining the InSAR-derived results and topographic change features, the relationship between the ground deformation and large-scale land creation was further analyzed. The results indicated that the MECC project in the YND has created over 22 km2 of flat land, including 10.8 km2 of filled area, with a maximum fill thickness of ~110 m. Significant uneven ground deformation was detected in the land-creation area, with a maximum subsidence rate of approximately 121 mm/year, which was consistent with the field survey. The strong correlation between the observed subsidence patterns and the land creation project suggested that this recorded uneven subsidence was primarily related to the spatial distribution of the filling works, along with the changes in the thickness and geotechnical properties of the filled loess; moreover, rapid urbanization, such as road construction, can accelerate the subsidence process. These findings can guide improvements in urban planning and the mitigation of geohazards in regions experiencing large-scale land construction.

Highlights

IntroductionThe Loess Plateau, covering an area of approximately 440,000 km in north-central
The main objectives of this study are (1) to characterize the spatiotemporal patterns of the topographic changes and land subsidence associated with the Mountain Excavation and City Construction’ (MECC) project in the Yan’an New District (YND), and (2) to quantify the relationships between land subsidence and the MECC project in the YND
Wu et al (2019) assessed the spatiotemporal patterns of the subsidence in the YND based on the small baseline subset interferometric synthetic aperture radar (InSAR) (SBAS-InSAR) technique, and confirmed the ability of the SBAS-InSAR method to detect surface deformation in the land creation region; the results indicated that the land subsidence is mainly caused by earth filling and building loads [5]

Summary

Introduction

The Loess Plateau, covering an area of approximately 440,000 km in north-central. China, is the most widely distributed, thickest loess area in the world [1]. With the rapid promotion of the ‘western development strategy’ and the ‘Belt and Road’ policy in China, several mega engineering projects have been underway on the Loess Plateau, such as the ‘Mountain Excavation and City Construction’ (MECC) [2], the ‘Gully Control and Highland Protection’ (GCHP) [3] and the ‘Gully Land Consolidation’ (GLC) [4]. We illustrate an integrated approach which uses space-borne optical photogrammetry, InSAR techniques and field surveys to investigate the topographic changes and ground deformation due to the large-scale MECC project and their interactions

Objectives

Methods

Results

Discussion

Conclusion