Long-term flood-hazard modeling for coastal areas using InSAR measurements and a hydrodynamic model: The case study of Lingang New City, Shanghai

In this paper, we study long-term coastal flood risk of Lingang New City, Shanghai, considering 100- and 1000-year coastal flood return periods, local seal-level rise projections, and long-term ground subsidence projections. TanDEM-X satellite data acquired in 2012 were used to generate a high-resolution topography map, and multi-sensor InSAR displacement time-series were used to obtain ground deformation rates between 2007 and 2017. Both data sets were then used to project ground deformation rates for the 2030s and 2050s. A 2-D flood inundation model (FloodMap-Inertial) was employed to predict coastal flood inundation for both scenarios. The results suggest that the sea-level rise, along with land subsidence, could result in minor but non-linear impacts on coastal inundation over time. The flood risk will primarily be determined by future exposure and vulnerability of population and property in the floodplain. Although the flood risk estimates show some uncertainties, particularly for long-term predictions, the methodology presented here could be applied to other coastal areas where sea level rise and land subsidence are evolving in the context of climate change and urbanization

Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR tomography

This book focuses on remote sensing for urban deformation monitoring. In particular, it highlights how deformation monitoring in urban areas can be carried out using Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions show the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. Some of them show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This book is dedicated to the technical and scientific community interested in urban applications. It is useful for choosing the appropriate technique and gaining an assessment of the expected performance. The book will also be useful to researchers, as it provides information on the state-of-the-art and new trends in this fiel

Monitoring land subsidence of airport using InSAR time-series techniques with atmospheric and orbital error corrections

Land subsidence is one of the common geological hazards worldwide and mostly caused by human activities including the construction of massive infrastructures. Large infrastructure such as airport is susceptible to land subsidence due to several factors. Therefore, monitoring of the land subsidence at airport is crucial in order to prevent undesirable loss of property and life. Remote sensing technique, especially Interferometric Synthetic Aperture Radar (InSAR) has been successfully applied to measure the surface deformation over the past few decades although atmospheric artefact and orbital errors are still a concerning issue in this measurement technique. Multi-temporal InSAR, an extension of InSAR technique, uses large sets of SAR scenes to investigate the temporal evolution of surface deformation and mitigate errors found in a single interferogram. This study investigates the long-term land subsidence of the Kuala Lumpur International Airport (KLIA), Malaysia and Singapore Changi Airport (SCA), Singapore by using two multi-temporal InSAR techniques like Small Baseline Subset (SBAS) and Multiscale InSAR Time Series (MInTS). General InSAR processing was conducted to generate interferogram using ALOS PALSAR data from 2007 until 2011. Atmospheric and orbital corrections were carried out for all interferograms using weather model, namely European Centre for Medium Range Weather Forecasting (ECMWF) and Network De-Ramping technique respectively before estimating the time series land subsidence. The results show variation of subsidence with respect to corrections (atmospheric and orbital) as well as difference between multi-temporal InSAR techniques (SBAS and MInTS) used. After applying both corrections, a subsidence ranging from 2 to 17 mm/yr was found at all the selected areas at the KLIA. Meanwhile, for SCA, a subsidence of about less than 10 mm/yr was found. Furthermore, a comparison between two techniques (SBAS and MInTS) show a difference rate of subsidence of about less than 1 mm/yr for both study area. SBAS technique shows more linear result as compared to the MInTS technique which shows slightly scattering pattern but both techniques show a similar trend of surface deformation in both study sites. No drastic deformation was observed in these two study sites and slight deformation was detected which about less than 20mm/yr for both study areas probably occurred due to several reasons including conversion of the land use from agricultural land, land reclamation process and also poor construction. This study proved that InSAR time series surface deformation measurement techniques are useful as well as capable to monitor deformation of large infrastructure such as airport and as an alternative to costly conventional ground measurement for infrastructure monitoring

Assessing the accuracy of ALOS/PALSAR-2 and Sentinel-1 radar images in estimating the land subsidence of coastal areas: a case study in Alexandria city, Egypt

Recently, the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique is widely used for quantifying the land surface deformation, which is very important to assess the potential impact on social and economic activities. Radar satellites operate in different wavelengths and each provides different levels of vertical displacement accuracy. In this study, the accuracies of Sentinel-1 (C-band) and ALOS/PALSAR-2 (L-band) were investigated in terms of estimating the land subsidence rate along the study area of Alexandria City, Egypt. A total of nine Sentinel-1 and 11 ALOS/PALSAR-2 scenes were used for such assessment. The small baseline subset (SBAS) processing scheme, which detects the land deformation with a high spatial and temporal coverage, was performed. The results show that the threshold coherence values of the generated interferograms from ALOS-2 data are highly concentrated between 0.2 and 0.3, while a higher threshold value of 0.4 shows no coherent pixels for about 80% of Alexandria’s urban area. However, the coherence values of Sentinel-1 interferograms ranged between 0.3 and 1, with most of the urban area in Alexandria showing coherent pixels at a 0.4 value. In addition, both data types produced different residual topography values of almost 0 m with a standard deviation of 13.5 m for Sentinel-1 and −20.5 m with a standard deviation of 33.24 m for ALOS-2 using the same digital elevation model (DEM) and wavelet number. Consequently, the final deformation was estimated using high coherent pixels with a threshold of 0.4 for Sentinel-1, which is comparable to a threshold of about 0.8 when using ALOS-2 data. The cumulative vertical displacement along the study area from 2017 to 2020 reached −60 mm with an average of −12.5 mm and mean displacement rate of −1.73 mm/year. Accordingly, the Alexandrian coastal plain and city center are found to be relatively stable, with land subsidence rates ranging from 0 to −5 mm/year. The maximum subsidence rate reached −20 mm/year and was found along the boundary of Mariout Lakes and former Abu Qir Lagoon. Finally, the affected buildings recorded during the field survey were plotted on the final land subsidence maps and show high consistency with the DInSAR results. For future developmental urban plans in Alexandria City, it is recommended to expand towards the western desert fringes instead of the south where the present-day ground lies on top of the former wetland areas.Published versio

A GeoNode-based platform for an effective exploitation of advanced DInSAR measurements

This work presents the development of an efficient tool for managing, visualizing, analysing, and integrating with other data sources, the deformation time-series obtained by applying the advanced differential interferometric synthetic aperture radar (DInSAR) techniques. To implement such a tool we extend the functionalities of GeoNode, which is a web-based platform providing an open source framework based on the Open Geospatial Consortium (OGC) standards, that allows development of Geospatial Information Systems (GIS) and Spatial Data Infrastructures (SDI). In particular, our efforts have been dedicated to enable the GeoNode platform to effectively analyze and visualize the spatio/temporal characteristics of the DInSAR deformation time-series and their related products. Moreover, the implemented multi-thread based new functionalities allow us to efficiently upload and update large data volumes of the available DInSAR results into a dedicated geodatabase. The examples we present, based on Sentinel-1 DInSAR results relevant to Italy, demonstrate the effectiveness of the extended version of the GeoNode platform

Sedimentation and consolidation behaviour of fly ash-based geopolymer stabilised dredged mud

Ports conduct maintenance and capital dredging campaigns to maintain channel depths, improve navigational safety of vessels, and to cater for larger ships with deeper draughts. Most of the soft dredged material derived from these dredging campaigns is beneficially used as a fill material for land reclamation purposes. Port authorities undertake land reclamation works to address land scarcity and environmental constraints that are associated with dredged material placement alternatives. Land reclaimed with soft dredged mud has geotechnical challenges of slow self-weight consolidation, high compressibility and low bearing capacity. To overcome these geotechnical challenges and to alleviate risk of structures settlement, dredged material stabilisation techniques such as chemical admixtures, electrokinetic, stone columns, prefabricated vertical drains (PVDs), and surcharging are implemented. For these existing dredged material stabilisation methods to be applicable, the land reclamation fill material must have settled, consolidated and gained sufficient strength and stiffness to be traversed by ground improvement plant and workforce. By then, the reclaimed (the man-made) ground becomes similar to a naturally formed soft ground that civil and geotechnical engineers have no control on its soft soil formation processes. On dredging and land reclamation with soft dredged mud slurry project site, dredge cutters and drag heads rip and disintegrate marine sediment turning it into high water content dredged mud slurry. Then, the dredged mud slurry is pumped into land reclamation containment ponds to settle and self-weight consolidate to form soft land reclamation fill material. The dredged mud slurry takes several hours from the moment it is placed into containment ponds to the commencement of the land reclamation fill material formation. This time slot is sufficient for an early geotechnical intervention to stabilise the dredged mud while it is still in its slurry stage, prior to the formation of the soft land reclamation fill material. Stabilising the soft dredged mud slurry provides an opportunity to manipulate its sedimentation behaviour that controls microstructure, consolidation and compressibility characteristics of the resulting land reclamation fill material. This research study has investigated feasibility of stabilising 400% water content dredged mud slurry that is derived from Port of Townsville, Queensland Australia, using fly ash-based geopolymer binder at 6%, 12% and 18% by weight. The fly ash-based geopolymer binder is chosen for its tolerance to high water content nature of the dredged mud slurry, binding attributes, cost effectiveness, and environmental benefits. The study examined the influence of the fly ash-based geopolymer stabilisation on the sedimentation and consolidation behaviours, mineralogy and microstructure of the fly ash-based geopolymer stabilised dredged mud. Settling column tests were conducted to investigate the sedimentation behaviour of untreated and fly ash-based geopolymer stabilised dredged mud slurries. Standard one-dimensional consolidation (Oedometer) tests were used to evaluate the compressibility and consolidation characteristics of the untreated and the fly ash-based geopolymer stabilised dredged mud sediments. X-ray diffractometer (XRD) and scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) techniques were deployed to analyse the mineralogy and microstructure of the untreated and the fly ash-based geopolymer stabilised dredged mud. The study found it is feasible to stabilise high water content dredged mud slurry with fly ash-based geopolymer binder. Fly ash-based geopolymer gel coating dredged mud particles in the slurry was found to be the main stabilisation mechanism. It is noted the geopolymer gel coating dredged mud particles in the slurry has exacerbated flocculation of the stabilised dredged mud slurry, extended its flocculation duration, reduced settling time and shorten overall sedimentation duration. The SEM with EDS analysis showed the fly ash-based geopolymer stabilisation has altered the microstructure of stabilised dredged mud, changed its particles arrangement and reduced its desiccation shrinkage cracks. Subsequently, the fly ash-based geopolymer stabilisation has improved the compressibility and consolidation properties of the stabilised dredged mud by reducing its coefficient of volume compressibility (mᵥ) and increasing its coefficient of consolidation (cᵥ) and permeability coefficient (k). However, the XRD analysis found no correlation between the fly ash-based geopolymer stabilisation and the mineralogy of the fly ash-based geopolymer stabilised dredged mud

Land Surface Monitoring Based on Satellite Imagery

This book focuses attention on significant novel approaches developed to monitor land surface by exploiting satellite data in the infrared and visible ranges. Unlike in situ measurements, satellite data provide global coverage and higher temporal resolution, with very accurate retrievals of land parameters. This is fundamental in the study of climate change and global warming. The authors offer an overview of different methodologies to retrieve land surface parameters— evapotranspiration, emissivity contrast and water deficit indices, land subsidence, leaf area index, vegetation height, and crop coefficient—all of which play a significant role in the study of land cover, land use, monitoring of vegetation and soil water stress, as well as early warning and detection of forest fires and drought

Book of short Abstracts of the 11th International Symposium on Digital Earth

The Booklet is a collection of accepted short abstracts of the ISDE11 Symposium

ALOS-2/PALSAR-2 Calibration, Validation, Science and Applications

Twelve edited original papers on the latest and state-of-art results of topics ranging from calibration, validation, and science to a wide range of applications using ALOS-2/PALSAR-2. We hope you will find them useful for your future research