Land Subsidence Velocity Research Articles

Adjacent-Track InSAR Processing for Large-Scale Land Subsidence Monitoring in the Hebei Plain

Large-scale land subsidence has threatened the safety of the Hebei Plain in China. For tens of thousands of square kilometers of the Hebei Plain, large-scale subsidence monitoring is still one of the most difficult problems to be solved. In this paper, we employed the small baseline subset (SBAS) and NSBAS technique to monitor the land subsidence in the Hebei Plain (45,000 km2). The 166 Sentinel-1A data of adjacent-track 40 and 142 collected from May 2017 to May 2019 were used to generate the average deformation velocity and deformation time-series. A novel data fusion flow for the generation of land subsidence velocity of adjacent-track is presented and tested, named as the fusion of time-series interferometric synthetic aperture radar (TS-InSAR) results of adjacent-track using synthetic aperture radar amplitude images (FTASA). A cross-comparison analysis between the two tracks results and two TS-InSAR results was carried out. In addition, the deformation results were validated by leveling measurements and benchmarks on bedrock results, reaching a precision 9 mm/year. Twenty-six typical subsidence bowls were identified in Handan, Xingtai, Shijiazhuang, Hengshui, Cangzhou, and Baoding. An average annual subsidence velocity over −79 mm/year was observed in Gaoyang County of Baoding City. Through the cause analysis of the typical subsidence bowls, the results showed that the shallow and deep groundwater funnels, three different land use types over the building construction, industrial area, and dense residential area, and faults had high spatial correlation related to land subsidence bowls.

Land subsidence estimation using DinSAR method ALOS PALSAR image in Padang City West Sumatra, Indonesia

Land subsidence is a phenomenon that occurs in big cities around the world and in Indonesia. Padang as one of the largest cities in West Sumatera also facing land subsidence due to natural phenomena and human induced. Padang City is located at the west coast of Sumatera Island which is the junction point of three active plates that cause frequent earthquakes. Main goals of this research are to know the distribution of area affected by land subsidence, to know the estimated value of land subsidence and to know the value of the velocity of land subsidence in Padang area using DInSAR method. The data used in this study is ALOS PALSAR Image Level 1.1 of Padang city during 2007 to 2010 was obtained through JMRSL CERES Chiba University, Japan and collected through Alaska Satellite Facility website. Differential Interferometric Synthetic Aperture Radar (DInSAR) is a technique considered to be one of the most efficient technique for detecting land subsidence. The DInSAR method is used in mapping altitude changes developed into a land-subsidence map each year. The mapping results show the distribution of the areas affected by the maximum land subsidence in Padang area of West Sumatera are Padang Utara, Nanggalo, and Padang Barat Subdistricts. The land subsidence insignificant occurred is Padang Selatan and Lubuk Begalung Subdistricts. The estimated value of the land subsidence distribution in Padang area using DInSAR method has decreased significantly after the earthquake of September 30, 2009 in Padang Utara, Nanggalo and West Padang Subdistricts is around 0 - 32.70 cm, and the value of land subsidence velocity is around 0.13 - 12 cm/year. One of the expected effects of land subsidence can be increased in the area susceptible for flooding in Padang city.

Land subsidence induced by underground coal mining at Quang Ninh, Vietnam: persistent scatterer interferometric synthetic aperture radar observation using Sentinel-1 data

ABSTRACT Land subsidence occurs in Ha Long and Cam Pha cities due to human activities in which the underground coal mining exploitation plays a crucial responsibility. For mapping the spatial distribution of this phenomenon and monitoring its evolution over the time, the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) approach was applied to 56 Sentinel-1A images, captured from June 2015 to June 2019. This approach allows monitoring ground displacement by continuously measuring the position of objects that persistently scatter radar beams. This interferometric synthetic aperture radar (InSAR) technique extracts deformation signals and it can be applied to areas where the discontinuous land subsidence is occurring. The mean land subsidence velocity map shows that two principal areas in Ha Long city including Ha Lam, Ha Trung, Ha Khanh, and Ha Tu wards, and Cam Pha city, specifically Mong Duong ward have been subsided in recent years with the maximum velocity of 14.5 mm year−1 and a cumulative displacement ranging from 30 to 50 mm in the Line Of Sight (LOS) direction over 4 years. Field investigation recognized the direct impact of this phenomenon on houses, infrastructures, and natural features located above the underground coal mining utilities. This hazard has a close relationship with the exploiting process of coal seams, which alternately lay inside the sedimentary layers of the Hon Gai formation.

Ground Deformation of Wuhan, China, Revealed by Multi-Temporal InSAR Analysis

Wuhan, the largest city in central China, has experienced rapid urban development leading to land subsidence as well as environmental concerns in recent years. Although a few studies have analyzed the land subsidence of Wuhan based on ALOS-1, Envisat, and Sentinel-1 datasets, the research on long-term land subsidence is still lacking. In this study, we employed multi-temporal InSAR to investigate and reveal the spatiotemporal evolution of land subsidence over Wuhan with ALOS-1, Envisat, and Sentinel-1 images from 2007–2010, 2008–2010, 2015–2019, respectively. The results detected by InSAR were cross-validated by two independent SAR datasets, and leveling observations were applied to the calibration of InSAR-derived measurements. The correlation coefficient between the leveling and InSAR has reached 0.89. The study detected six main land subsidence zones during the monitoring period, with the maximum land subsidence velocity of −46 mm/a during the 2015–2019 analysis. Both the magnitude and the extent of the land subsidence have reduced since 2017. The causes of land subsidence are discussed in terms of urban construction, Yangtze river water level changes, and subsurface water level changes. Our results provide insight for understanding the causes of land subsidence in Wuhan and serve as reference for city management for reducing the land subsidence in Wuhan and mitigating the potential hazards.

An approach for multi-dimensional land subsidence velocity estimation using time-series Sentinel-1 SAR datasets by applying persistent scatterer interferometry technique

The time-series interferometric synthetic aperture radar (InSAR) techniques has the potential of estimating the land subsidence at a high accuracy of nearly in millimeter scale. The major limitation of the present InSAR methods like persistent scatterer interferometry (PSI) is that they measure land deformation velocities only in the direction of the radar line of sight (LOS). Hence, the real prospects of the deformation velocity, i.e. the horizontal and vertical components of velocity remain uncertain. This study is focusing on retrieving PSI based multi-dimensional land deformation velocity along horizontal and vertical directions in an urban region by using ascending and descending pass Sentinel-1 datasets. The area for this study is Lucknow city in Uttar Pradesh state of India. The estimated LOS velocity vectors from ascending and descending pass time-series datasets are utilized for retrieving multidimensional subsidence velocity. Further, the retrieved time-series land subsidence is correlated to the groundwater level variation during the considered time span.

Estimation of groundwater abstraction induced land subsidence by SBAS technique

The groundwater over pumping induced land subsidence is one of the major geological hazards in the alluvial aquifers. The objective of this study is to assess the rate of land subsidence in Kolkata metropolitan area, India. Land subsidence can be estimated with high precision by Small Baseline Subset (SBAS) analysis. The advantages of this method are generation of a mean deformation map. The ENVISAT ASAR data acquired at six different periods over the study site were processed by SBAS technique. The decline in the piezometric head from the year 2003 to 2010 was about 6 m. Land subsidence velocity was ~8 mm/year at Salt Lake City and Science City (near the eastern metropolitan bypass). The major cause for land subsidence is over pumping of groundwater from the confined aquifers in these areas. There is a reasonable comparison between the maximum region of land subsidence and low value piezometric head contours confirming that the over extraction of the confined aquifer of this region is responsible for land subsidence. It is necessary to control the groundwater pumping so as to arrest the declining trend of piezometric head of study area for managing the problem of land subsidence. Hence, the possible remedial measures that can be taken are reducing groundwater pumping in the study region.

Multi-scale geotechnical features of dredger fills and subsidence risk evaluation in reclaimed land using BN

Shanghai has the largest newly reclaimed area in China’s coastal regions, and dredger fills are universally distributed in reclaimed lands there. Multi-scale geotechnical properties of dredger fills in region-scale (>1 km2), site-scale (1 m2–1 km2), mesoscale (1 cm2–1 m2), and microscale (1 µm2–1 cm2) were studied mainly through cone penetration investigation, borehole investigation, and microscopic inspections. Dredger impact craters, soil structures, and soil textures were investigated qualitatively and quantitatively to identify the dredger fills. Ultimate land subsidence since 1 July 2018 and land subsidence velocity characterized by the land subsidence from 1 July 2018 to 1 January 2019 were evaluated in Shanghai’s typical reclaimed regions. Afterwards, Bayesian network including sixteen variables was proposed for land subsidence risk assessment. Surface subsidence, land subsidence velocity, and comprehensive land subsidence were the most sensitive to data point location and average initial void ratio of underlying strata. These three risk variables were also highly correlated to the thickness of the dredger fill layer and the reclamation time. This finding indicates that variances of the four independent variables (i.e., data point location, average initial void of underlying strata, land reclamation time, and thickness of dredger fill layer) significantly decide variances of the three risk levels.

Risk assessment of land subsidence at Tianjin coastal area in China

Risk assessment and zoning are very important to risk management. In this study, a land subsidence risk assessment index was proposed based on the Disaster Risk Index. The cumulative subsidence volume, the land subsidence velocity, and the groundwater exploitation intensity were collected, analyzed, and put together to create a land subsidence hazard evaluation map in Tianjin coastal area. The population density, Gross Domestic Product per square kilometer, and construction land proportion were adopted as indexes to create the vulnerability map. In addition, the capability of land subsidence prevention and reduction was also assessed. Finally, the land subsidence risk map was created by combing the hazard, vulnerability, and the capability of land subsidence prevention and reduction map. Specifically, the land subsidence risk was classified into five levels, i.e., very high, high, medium, low, and very low. The result of this research could provide a solid basis for the sustainable development as well as disaster prevention policy-making of Tianjin city.

D-InSAR Technique for Land Subsidence Monitoring

The land subsidence has been a global disastrous problem, and the conventional geodetic technique is highly incompetent in the large-scale and serious land deformation monitoring. The D-InSAR technique has been widely applied and deeply researched in the field of the land deformation monitoring. This article first puts forward one of the methods known as time series radar interferometry based on permanent scatterers technique, and then, applies the time series analysis method into D-InSAR. This paper takes the phase difference of two nearer permanent scatterers in an interferogram as research object; therefore, the atmospheric delay impact can be eliminated. In the research, there are several steps including preprocessing radar images, selecting the PS points, combination of PS points, computing the variance of the phase difference for two PS points, integer least-squares adjustment, obtaining land subsidence velocity and so forth. The land subsidence data and the distribution map obtained in this paper by adapting this method to the experiment of Tianjin area subsidence monitoring have been proved to be satisfactory. The method for eliminating the atmospheric delay impact accurately has been realized by combining the time seriesmethod with PS technique. At the same time, it was confirmed that the time series for InSAR is a feasible and effective method for monitoring land deformation. Moreover, it can be concluded from the result obtained in the paper that the selection of PS points is so important that it is worthy studying further on.

Land subsidence caused by groundwater exploitation in the Hangzhou-Jiaxing-Huzhou Plain, China

Hangzhou-Jiaxing-Huzhou Plain in northern Zhejiang Province, located between the Yangtze and Qiantang Rivers, is one of the regions where economic development is most rapid in China. Geological and hydrogeological surveys reveal a multi-layered aquifer system beneath the plain, which includes Holocene phreatic water layers and Pleistocene confined aquifers. Based on the historical records of groundwater extraction, groundwater levels, and ground settlement from 1964 to 2000, it is shown that ground subsidence has resulted from the continuously increasing extraction of groundwater from deep confined aquifers, and that the evolution of land subsidence can be characterized by a multifractal model. Based on this model, a set of empirical power-law relations have been established between: the land subsi- dence velocity and the annual groundwater extraction; groundwater drawdown and the annual land subsidence velocity; and the amount of land subsidence and the associated area of land. A set of indices are proposed for evaluating dynamic evolution of groundwater exploitation and land subsidence for the Hang-Jia-Hu Plain, from which the critical degree of evolution of land subsidence in the near future can be estimated using data on groundwater exploitation and water level changes.