ALBERT

Beschreibung: The Sacramento-San Joaquin Delta is at the heart of California's water supply system that provides water for irrigation and human consumption. It is also home to subsiding organic soils, decreasing native aquatic species populations, water quality degradation, vulnerable levees (levees are equivalent to dikes) and decreasing agricultural viability. There has been substantial progress in the interdisciplinary understanding and quantification of the nature and effects of subsidence and its mitigation. Because of the need for a drained rootzone, farming of crops such as vegetables, trees, vines, corn and alfalfa, results in an ongoing unsustainable cycle of continuing peat oxidation and deepening of drainage ditches to compensate for elevation loss. Despite substantial evidence for the increasing risks to the State's economy and water supply, the unsustainability of the status quo, and evidence for the benefits of alternatives, there has been limited progress in converting to land uses that can reduce, stop and reverse subsidence. Our overall approach has been to measure land-surface elevation changes; understand, quantify and model subsidence and greenhouse gas emissions from drained organic soil, and evaluate alternate land uses. Subsidence rates vary from less than 0.5 to over 2 cm yr−1, depending primarily on depth to groundwater and soil organic matter content. The primary cause of subsidence is the oxidation of organic matter, which has resulted in elevations of −3 to −9 m on about 100 000 ha. Using the results from micrometeorological measurements and modelling, we estimate that organic-matter oxidation causes an annual emission of over 2×106 t of CO2-equivalent which represents about 21 % of the State's plant-based agricultural emissions. Rewetting of the peat soils is emerging as a viable solution. Rice and wetlands stop and (in the case of wetlands) reverse the effects of subsidence and result in a net greenhouse-gas emission reduction benefit. Wetlands accrete about 3 cm of soil per year, can break the unsustainable subsidence/drainage cycle, reverse the trajectory of increasing hydraulic pressures on levees, reduce the probability of levee failure and seepage onto islands (islands are equivalent to polders), and may provide material for biofuels and animal feed. The recent implementation of a methodology for quantification of the GHG benefit is facilitating land use conversion and participation in the carbon market.

Beschreibung: Taiwan is an oceanic nation with an area of approximately 36 000 km2. The Central Mountain Range was formed by the Eurasian and Philippine plates and stretches along the entire island from north to south, along the entire island, thus forming a natural line of demarcation for rivers on the eastern and western sides of the island. Pingtung Plain is formed by Quaternary alluvial fan material from the three main rivers. The aquifers comprise very coarse permeable sands and gravels under phreatic conditions in the north and less permeable sands under confined or even artesian conditions in the southern part of Pingtung Plain. The natural groundwater source is mainly from direct rainfall percolation and infiltration from the three main rivers, with their catchments lying partly outside the plain. The uncontrolled development of groundwater resources has led to undesirable effects, especially in the south, where aquaculture is concentrated. These effects are land subsidence, saline water intrusion, and lowering of water tables. It is thus one of the important key strategies in the solution of land subsidence, water resource development and flood control for sustainable development named Benefited Water Reuse from Storm Water in Pingtung, Taiwan. A serious of studies for this issue has been carried out. The feasibility study phase of the Artificial Recharge of Groundwater Project (ARGP) for Pingtung, Taiwan, was then implemented in 1997 using a MODFLOW simulation and an optimal model. Through the managed aquifer recharge model, the aquifer storage increases and the inundation scale decreases with land subsidence of the coastal area, as aimed at by the purpose of the controlled groundwater level. Infiltration mechanism simulation of artificial groundwater recharge, with the TOUGH2 model, was used to simulate the high infiltration behaviour in sequence in 2010. Both publications have been confirmed and approved by the Central Government and then approved by the environmental impact assessment. The ARGP was then implemented in May 2018 and operated for one wet season for the first phase with 50 ha and a total of 300 ha from May to October 2018. The sedimentation over the top of the recharge basin forms the clogging mechanism which has been analysed. The operation experience can further provide the mechanism process for research reference. The project, once implemented, can improve and mitigate land subsidence as well as formulate water banks for adapting and managing aquifer recharge.

Beschreibung: In the Southern Kanto Gas Field, natural gas dissolved in water has been produced for over 80 years. In order to produce the natural gas dissolved in water, formation water must be pumped from a reservoir in the gas field. The production of formation water is considered to be one of the causes of land subsidence. Because brine injection into shallow formations is expected to be effective to mitigate land subsidence, our association is planning to conduct the pilot test study. In this test, the production and injection of brine are going to be performed, and we will observe a deformation of the shallow formation and a change of ground level and the bottom hole pressure. As a result of these tests, if the land subsidence mitigation effect by injection into shallow formation is confirmed, it is expected that it will be connected to increased production and to reservoir management in consideration of land subsidence mitigation in the future.

Beschreibung: In order to analyze land subsidence caused by the dewatering of a deep foundation pit in Shanghai, numerical analysis, field testing, automatic monitoring and other technologies are applied to research land subsidence control technologies, covering the whole process during the design, construction and operation of foundation pit dewatering systems. The key technologies are applied to a typical metro station foundation pit in Shanghai, such as the integrated design of foundation pit dewatering and a waterproof curtain, information control, groundwater artificial recharge, etc. The measured data of groundwater level, pore water pressure and land subsidence show a good effect on land subsidence prevention and control.

Beschreibung: Land subsidence in the Netherlands is an ongoing process. An increasing number of people and economic assets are exposed to subsidence and damage costs are soaring. In some areas tipping points have already been reached, where current land-use can no longer be maintained without considerable costs. A specific policy focusing on subsidence is lacking. Dealing with the societal impacts of subsidence is mainly the (implicit) responsibility of the public authorities that regulate the drivers of subsidence. As the societal impacts continue to occur and are increasing, discussions arise on the exact drivers of subsidence and responsibilities for the impacts on society. Our study aims to analyse whether and to what extent public decision-making, which controls land subsidence due to groundwater-table lowering and extraction of hydrocarbons and its societal impacts, is organised effectively to reduce these societal impacts, and how the legal framework can be improved to achieve that. By studying the respective legal frameworks of these drivers, we map legal solutions for mitigation of subsidence itself or adaptation to its societal impacts – both eventually aimed at reducing the societal impacts of subsidence. In this paper, we focus on the legal framework of one of these drivers: groundwater-table lowering.

Beschreibung: The Ebro Delta is a highly vulnerable Mediterranean coastal ecosystems located on the northern Mediterranean coast of Spain. Determining its subsidence rate and sources is a key issue for the present and future management of this area. Differential Interferometry Synthetic Aperture Radar (DInSAR) compared with the contribution to subsidence of the compaction of delta's sediments and the lithosphere's deformation, indicated a general Ebro Delta subsidence ranging from

Beschreibung: Shanghai has a long history of exploitation and utilization of groundwater in order to meet the needs of industrial production and residential water. As a result, serious land subsidence disasters were induced. Land subsidence poses a huge security threat to the low-altitude coastal city of Shanghai. The development of land subsidence in Shanghai is closely related to the exploitation of underground water. In order to control land subsidence disasters, Shanghai has taken three key measures, i.e., the amount of compressed groundwater exploitation, the adjustment of groundwater exploitation level, and the implementation of artificial groundwater recharge, which have become the most effective measures for land subsidence control. However, as the groundwater levels of various aquifers in the region rise sharply, land subsidence is effectively controlled, and the measures of groundwater exploitation and recharge need to be dynamically adjusted to adapt to the current situation. In this context, from the perspective of history, the paper analyzes the long-term groundwater exploitation and recharge process and the development characteristics of land subsidence in Shanghai and studies the evolution process of land subsidence in different stages. From the perspective of land subsidence prevention and control, the paper analyzes the management measures of groundwater exploitation and recharge and the great achievements. The research results can provide a basis for land subsidence control and comprehensive groundwater management in the new period and can also provide a demonstration and reference for groundwater resource management in similar areas.

Beschreibung: Aguascalientes valley, located in the central part of México, is affected for a land subsidence process triggered by groundwater withdrawal since the 1980's. Currently, the occurrence and the reactivation of surface faults and earth fissures due to differential subsidence, is the main concern for government bureaus dealing with urban planning, because of the damages that these terrain discontinuities are able to cause in constructions and infrastructure. The deformation and rupture process produces an active linear discontinuity with a variable width of influence, where the constructions and infrastructure are prone to get damage. Therefore, the determination of this width of influence is critical for urban planning and hazard determination. In this work, the results of a geophysical seismic survey carried out in six surface discontinuities located in the subsidence area of the Aguascalientes Valley, are presented and discussed. The study included acquisition of seismic tomography profiles measured perpendicularly to the discontinuities, in order to obtain the P-wave velocity sections. The resulted P-wave velocity models show a low-velocity anomaly within the fracture trace with widths from 50 to 100 m. This anomaly is interpreted as a mechanically disturbed zone due to the activity of the surface fault, this is, due to the presence of fracturing caused to the adjacent material by the differential subsidence. The results suggest that the material in the disturbed zone, is experiencing a increase in secondary porosity, caused by the deformation and rupture process, and the subsequent generation of small fissures and voids. The results of this study have practical implications because the methodology allows defining the influence zone of an active discontinuity, and therefore, to establish a restricted width along the surface discontinuity. The definition of this restraint zone is a first step to produce a subsidence hazard zoning including not only the discontinuity trace but its width of influence.

Beschreibung: Since the development of the coastal areas near present-day Houston, Texas, USA, subsidence has been a significant public policy concern. Subsidence in this area is caused by the extraction of groundwater from the Coastal Lowlands aquifer system, locally referred to as the Gulf Coast Aquifer. Concerns associated with subsidence in the Houston area include coastal inundation from storm surge, inland flooding, and critical infrastructure damage. The Houston area receives about 126 cm of precipitation each year, making flooding a critical issue in the region. The Houston area is the 4th largest city in the United States with a population of about 6.89 million (2017) and has a total water demand of about 4 Mm3 per day (2017). In the 1950s the City of Houston began the development of several reservoirs to provide water for the rapidly growing city. In 1975, following decades of subsidence totaling over 3 m, the Harris-Galveston Subsidence District (District) began regulating the use of groundwater and shifting the primary water supply for the region from groundwater to treated surface water to cease on-going and prevent future subsidence. Leveraging the alternative resources developed by the City of Houston in the 1950s, the District's regulatory framework focuses on spatial prioritization and the systematic conversion to alternative source waters. The District's regulatory plan includes three planning areas. Currently, the regional water authorities and the City of Houston are developing nearly five billion dollars (USD) in infrastructure to produce and deliver an additional 1.2 Mm3 per day of treated surface water to Houston and the surrounding communities. Resource development, public engagement, and political foresight have resulted in a reasonable approach to shift source waters and implement a plan to dramatically reduce and stop subsidence in the region. Figure 2 presents subsidence rates (2017) by regulatory area. Results show that the implementation of the regulatory program has substantially slowed subsidence in Areas 1 and 2, where full conversion has taken place. Planning the future water needs of the Houston area resulted in a robust and effective collaboration between the regulated community and the District. Analysis of historical source water use, aquifer response, and subsidence in the Houston area shows that the reasonable management of groundwater use in the Houston region is vital for the long-term prevention of subsidence and increases the resilience of the entire region.

Beschreibung: Since 1960s, Artificial Recharge has been adopted to control the geological disaster of land subsidence in Shanghai. The water source to recharge to the confined aquifer meet the Standard for Drinking Water Quality which comes from the Huangpu River or Yangtze River. Thinking the difference between the primary environment of deep confined aquifer and the surface water, the recharge will exert an impact on the quality of groundwater in the deep confined aquifer, as well as to obtain satisfactory effects of land subsidence prevention.This paper focused on the change rules of the elements such as Cl based on long term tracking and monitoring data from one artificial recharge testing field. And research the solute transport characteristics in deep confined aquifer during artificial recharge. On the bases of these analysis, this paper presented the degree and scope of influence to deep confined aquifer in the process of artificial recharge.

Beschreibung: Accurately assessing the impact of groundwater exploitation on land subsidence can provide scientific support for decision-makers. This article establishes a groundwater–subsidence model in a typical area using the land subsidence characteristics of Tongzhou, China, and subsequently classifies a land subsidence early warning zone based on the land subsidence rate. Results show that land subsidence occurred throughout the whole Tongzhou District. The land subsidence that developed to the west of Liuzhuang, Tongzhou city and Taihu was the most serious The maximum annual subsidence rate reached 120 mm a−1 under the current groundwater extraction conditions, and the early warning level for land subsidence reached its highest level. If the pumping of groundwater was reduced by 50 % in the second and the fourth aquifers and by 60 % in the third aquifer, the land subsidence early warning level would be largely reduced and would meet the requirements for land subsidence control.

Beschreibung: For the levee strengthening project Krachtige IJsseldijken Krimpenerwaard (KIJK) a study has been done to examine all buildings along 10 km of levee. These buildings are an important factor in the design stage, because of its sensitivity to deformations due to the natural compaction of the soft deposits (creep) and the potential effects of the levee strengthening. This paper covers the quantification of building settlement due to natural subsidence using InSAR. Research is performed in the city archives to establish the characteristics of the buildings, such as the foundation type. Although the city archive is well organised, it is not complete. The building data density is substantially improved using InSAR information. This enhanced data set is a key factor in establishing an consistent assessment of the risk of damage for the different levee strengthening alternatives.

Beschreibung: In the Province of Flevoland, the Netherlands, land subsidence poses a problem to agriculture and water management. The peat layers in the soil are susceptible to compression and oxidation causing further subsidence. Applying subirrigation through the tile drain system to maintain saturation of the peat may be a measure to slow down subsidence. A study was therefore carried out at two sites, Nagele and Zeewolde, to assess the impact of subirrigation in the peat on the seasonal variation in soil moisture content, and corresponding redox conditions. Bacterial community analysis was carried out to verify the hydrochemical observations. Subirrigation proved to be an efficient measure to maintain a high water level in the peat soil as long as the permeability in the upper part of the peat was sufficient to allow transmission of water into the inter-drain area and when the peat layer extended enough below the minimum regional water level to prevent drainage to the sand layer underneath. The peat showed dual porosity and water levels could well be maintained by subirrigation at the Nagele site. At the Zeewolde site, the variability in the thin peat layer allowed drainage to occur in the sand layer, preventing subirrigation to maintain high water levels. However, at both sites the peat layer remained close to saturation throughout the summer, which may be caused by the fine-grained mineral layer isolating the peat from water extraction via evapotranspiration. Nitrate concentrations of up to 100 mg L−1 were observed were high (〉50 mg L−1) in the oxic mineral top layer but were low in the peat (0.3 mg L−1) at both Nagele and Zeewolde sites. Sulphate concentrations also showed a decrease with depth in the peat at Nagele, indicating a transition from sub-oxic above 1.5 m depth to anoxic conditions at 3.5 m depth. The hydrochemical observations in the soil moisture in the peat at Nagele confirmed that conditions were sub-oxic in the upper part of the peat (0.7 m below soil surface) to anoxic at greater depth (3.5 m). Soil microbe analyses showed few nitrification bacteria in the peat, whereas communities specialised in denitrification and ammonification were present, as well as sulphate reducing bacteria and methanogenic species. This confirmed the sub-oxic to anoxic conditions in the peat deduced from the hydrochemical observations. At Zeewolde, conditions remained sub-oxic throughout the profile.

Beschreibung: To analyze the generation of different ground fissure disasters, two typical ground fissures were selected. With geological survey and exploration data, the spatial characteristics of the Songzhuang and Gaoliying fissures were investigated. The different occurrence factors for the Songzhuang and Gaoliying fissures were analyzed based on geological structure and groundwater. The conclusions contain are as follows. The affected body of the Songzhuang fissure exhibits obvious tensile deformation, and it is not contact with buried faults. The fracture-affected body of the Gaoliying fissure shows obvious vertical dislocation and shear, and this is compounded with buried faults. The distribution characteristic of the Songzhuang fissure was controlled by the tectonics and the normal fault, while the buried fault not only control the distribution feature of the Gaoliying fissure but also controlled its deformation characteristic. A buried fault is the geological background for the formation of the Gaoliying fissure. The long-term exploitation of groundwater has caused the horizontal deformation of the soil and the rigid rotation of stratum in the subsidence edge. Both of them are the reason for the tensile deformation. Due to the activities of buried faults and differential subsidence in small areas, the affected bodies of the Gaoliying fissure showed vertical dislocation and shear deformation.

Beschreibung: In spite of subsidence being a well-studied geological phenomenon in Mexico City, its effects and risks for urban infrastructure and inhabitants have been neglected. Damage in the short, medium and long term implies maintenance and important mitigation costs. There are not systematic studies that address methodologies for the estimation of physical vulnerability of the geological media to fracture. In this work, factors conditioning the deformation and susceptibility to fracturing are analyzed using a deterministic approach. The identified physical variables were mapped, measured and integrated into a database that allowed for an adequate correlation of the parameters that condition fractures spatial distribution. A methodology for estimating a vulnerability index to fracturing (VIF) useful for decision making is proposed in this work.

Beschreibung: We report preliminary results of physical experiments of rupture occurrence and propagation associated with land subsidence driven by groundwater pumping and compare our analogue model results with corresponding previously reported numerical results. In particular, we aim to test the development of tensile stresses above a bedrock ridge that forms the base of an aquifer system. The experiment reproduces the main deformation and ruptures observed in field cases and in the numerical analysis.

Beschreibung: With the rapid growth of data volume and the development of artificial intelligence technology, deep-learning methods are a new way to model land subsidence. We utilized a long short-term memory (LSTM) model, a deep-learning-based time-series processing method to model the land subsidence under multiple influencing factors. Land subsidence has non-linear and time dependency characteristics, which the LSTM model takes into account. This paper modelled the time variation in land subsidence for 38 months from 2011 to 2015. The input variables included the change in land subsidence detected by InSAR technology, the change in confined groundwater level, the thickness of the compressible layer and the permeability coefficient. The results show that the LSTM model performed well in areas where the subsidence is slight but poorly in places with severe subsidence.

Beschreibung: Accurate monitoring of shallow subsidence in cultivated peatlands is a great challenge. Peat compaction by loading and peat oxidation by groundwater level lowering are two important processes contributing to shallow subsidence in cultivated peatlands, causing an overall increase in soil wetness over time and hence a lower soil-bearing capacity and agricultural production. Peat oxidation also causes emission of CO2 and other greenhouse gasses. Rigorous monitoring techniques are urgently needed to spatially and temporally map the amount and rate of subsidence and to monitor effects of measures to reduce subsidence and its negative impacts on livestock farming and agriculture. Monitoring shallow subsidence in peatlands is particularly challenging, because subsidence is a slow and spatially complex process, with average rates in the order of mm yr−1 but with higher rates possibly occurring on shorter timescales. The desired monitoring system must be able to capture this temporal and spatial variability, and preferably the contribution of different processes to total subsidence. The system needs to be applicable (technically- and financially-speaking) at regional scales, without severely impacting daily farming activities. To help design and test a subsidence monitoring system for cultivated peatland areas, four methods to measure subsidence are applied and assessed in a cultivated peatland in Overijssel (NL), namely spirit levelling, extensometery, LiDAR, and InSAR. In this paper, we focus on the levelling and extensometery methods and measurements. Subsidence was measured since October 2018 at eight livestock farms once every three months by levelling. In the same period, extensometers have measured vertical movement of (sub)surface levels hourly at two livestock farms. In addition, phreatic groundwater levels are continuously monitored. Preliminary results show vertical movements (up and down) in the order of centimeters on the timescale of weeks. These movements seem to be related to groundwater level fluctuations, but also evapotranspiration is expected to contribute to additional subsidence during the summer period. Because long term net subsidence is a slow process, additional data collection is needed to assess the different methods and the temporal and spatial fluctuations in subsidence on longer timescales. This is vital information to design the optimal method for monitoring subsidence in cultivated peatlands on large spatial scales, and to help in selecting effective measures to reduce subsidence and greenhouse gas emission in peatlands.

Beschreibung: Land subsidence can be caused by underground mining activities. Interferometric Synthetic Aperture Radar (InSAR) has became an economic, effective and accurate technique for land deformation survey and monitoring. In mining areas, there may be several factors to overcome for the succsessful application of InSAR, such as temporal decorrelation and detectable deformation gradient, that limit the ability of InSAR to monitoring rapid land subsidence. In this paper, images obtained by the Sentinel-1 satellite with 6 or 12 d revisiting time are used to improve the ability to detect a deformation gradient, and reduce the influence of temporal decorrelation. By combining Small Baseline Subsets (SBAS) and Interferometric Point Target Analysis (IPTA) methods, using the Nanhu mining area in Tangshan as an example, the spatial continuous results of land subsidence in this mining area are obtained with a 70 cm per year maximum rate, which clearly characterizes the deformation field and its deformation process. The results show that InSAR is a useful way to monitor land subsidence in a mining area and provides further data for environment mine restoration.

Beschreibung: Houston, Texas, is one of the earliest urban areas to employ Global Positioning System (GPS) technology for land subsidence and fault monitoring. As of 2020, the University of Houston and the Harris-Galveston Subsidence District have integrated over 230 permanent GPS stations into their routine GPS data processing for regional subsidence and fault monitoring. This article summarizes the GPS geodetic infrastructure in the Greater Houston region. The infrastructure is comprised of two components: a dense GPS network (HoustonNet) and a stable regional reference frame (Houston20). Houston20 is realized by 25 long-history (〉8 years) continuous GPS stations located outside the subsiding area and is aligned in origin and scale with the International GNSS Reference Frame 2014 (IGS14). The stability of the regional reference frame is below 1 mm yr−1 in all three directions. GPS-derived ground deformation rates (2010–2019) within the Greater Houston region are also presented in this article.

Beschreibung: The regular monitoring of the relative position of a sequence of radioactive bullets shot through the well of a vertical borehole can provide in-situ measurements of deep rock compaction. Developed in the '70s, this technology has experienced a growing interest in the '90s, but in recent years, its use and relevance in land subsidence management above producing hydrocarbon reservoirs have been often debated. The present communication analyses the state of the art of the radioactive marker technique and provides a critical review on the role that these measurements might play in the future evolution of land subsidence monitoring and modelling.

Beschreibung: Sinkholes are alarming and dangerous events, they have a worldwide occurrence, and are imposing a potential risk to urban communities and the widely developed built environment. Losses due to catastrophic sinkhole collapse, foundation, pavement and structural repairs, occur more often, due to the increased pressure to develop even on sinkhole prone land, and the aging of existing water supply infrastructure in the majority of cities. Remote sensing earth observation methods have proved to be valuable tools during the last two decades in long-term sinkhole hazard assessment. Satellite air borne and ground earth observation methods have primarily facilitated the wide detection of continuous displacement on the earth's crust. National sinkholes catalogues are necessary for town planers decision makers, and government authorities. In many instances the ground collapse is the result of water ingress from old poorly maintained leaking pipelines, or extensive dewatering activities. In the current study a comprehensive review of the current literature is presented in order to show experiences from South Africa and present recent mapping using PSInSAR methodology in Centurion South Africa.

Beschreibung: Advanced Differential Interferometric Synthetic Aperture Radar (A-DInSAR) techniques and 3-D groundwater flow and geomechanical models are integrated to improve our knowledge about the Tertiary detritic aquifer of Madrid (TDAM). In particular, the attention is focused on the Manzanares-Jarama well field, located to the northwest of Madrid, which experienced five cycles of extensive groundwater withdrawal followed by natural recovery, to cope with the droughts occurred in summer 1995, 1999, 2002, 2006, and 2009. Piezometric records and A-DInSAR data acquired by ERS-1/2 and ENVISAT satellites during the periods 1992–2000 and 2002–2010, respectively, have been used to calibrate the groundwater flow and the geomechanical models. A time-lag of about one month between the hydraulic head changes and the displacements of the land surface has been detected by a joint wavelet analysis of A-DInSAR and piezometer head time series. Overall, the results show the effectiveness of the proposed integrated approach composed of A-DInSAR and 3-D geomechanical model to characterize the aquifer-system response during and after the groundwater withdrawal.

Beschreibung: It is of great significance to reveal the mechanism of land subsidence to further find out the mechanism of leakage flow in multi-layer aquifer systems and the water-release compression of weak aquifers. In this paper, conditions of groundwater leakage flow are expounded, and the initial hydraulic gradient calculation formula in the aquitards are deduced. The data of Tianzhu Land Subsidence Monitoring Station are selected to preliminarily discuss the leakage flow mechanism of the multi-layer groundwater system and water-release compression of weak aquifers. The results show that, firstly the weak aquifer layers in the shallow strata above 91.32 m in Tianzhu Land Subsidence Station are all in the state of unidirectional drainage consolidation, and the water heads in the upper strata are higher than those in the lower strata. However, the hydraulic gradient between the two adjacent aquifers is smaller than the initial hydraulic gradient in the weak aquifer layer, so no leakage recharge effect is generated. Secondly, the water level of the two adjacent aquifers in the deep formation below 91.32 m shows a continuous downward trend, among which the weak aquifer is drained and consolidated on both sides, and the pore water head in the middle of the weak aquifer is the lowest. Although the strata has a large amount of compression, no leakage recharge phenomenon occurs. Thirdly, in a multi-layer aquifer system, when the head difference between adjacent aquifers is small and there is a thick viscous layer between them, it is difficult for the upper aquifer to overcome the shear strength of the bound water in the weak aquifer below, leaking recharge barely occurs.

Beschreibung: Layover occurs as a consequence of the slant range scale distortion in Synthetic Aperture Radar (SAR) data and it is commonly observed in the images acquired over urban areas. There may be two or more Persistent Scatterers (PSs) in one pixel. Moreover, these PSs do not have amplitude stability and spatial coherence. The threshold method used in the Persistent Scatterer Interferometric (PSI) SAR technique cannot identify the PS with two scatterers in urban, the accuracy of urban land subsidence is reduced. To solve this problem, we used Fast Fourier Transform (FFT) convert PSs in frequency domain during PS identification process of PSI, by observing their characteristics in the frequency domain, the layover scatterers can be identified and separated. The results of simulation experiment show that by analyzing the peak distribution characteristics of PSs in the elevation direction under the relatively even space baseline, PSI with FFT can identify single scatterers and layover scatterers. After separating the layover scatterers, the reliability of PSs identification are improved. For the real data experiment, we use 31 Sentinel-1A IW images covering Beijing from 2014 to 2016 as data sources. The results show that the proposed method can effectively identify layover scatterers which cannot be identified by the threshold method in urban, reducing the effect of layover scatterers, improving the accuracy of urban land subsidence monitoring.

Beschreibung: There are many factors causing land subsidence, and groundwater extraction is one of the most important causes of subsidence. A set of coupled partial differential equations are derived in this study by using the poro-elasticity theory and linear stress-strain constitutive relation to describe the one-dimensional consolidation in a saturated porous medium subjected to pore water pressure change due to groundwater table depression. Simultaneously, the closed-form analytical solutions for excess pore water pressure and total settlement are obtained. To illustrate the consolidation behavior of the poroelastic medium, the saturated layer of clay sandwiched between two sand layers is simulated, and the dimensionless pore water pressure changes with depths and the dimensionless total settlement as function of time in the clay layer are examined. The results show that the greater the water level change in the upper and lower sand layers, the greater the pore water pressure change and the total settlement of the clay layer, and the more time it takes to reach the steady state. If the amount of groundwater replenishment is increased, the soil layer will rebound.

Beschreibung: The report displays the characteristics of sedimentary environments, consolidation and consolidation settlements of the late Pleistocene–Holocene deposits in the Mekong Delta (MD) and Ho Chi Minh City (HCMC), Vietnam. The report furthermore discusses the influences of sedimentary environments on the consolidation properties and the resulting complex and large consolidation settlements. They cause land subsidence and uneven settlements of foundations in HCMC and the MD. They have especially combined with the unsuitable plans, land use like land fill in the lower land, rivers and ponds in the delta and increase in sea level by the global climatic change. As a result, it is very difficult to improve waterlogged areas in HCMC and the MD by the rain and tide waters. It is also not easy to propose a standard strategy for the management, planning and construction of these areas.

Beschreibung: Total subsidence in deltaic areas is the cumulative effect of a range of driving mechanisms, both natural and anthropogenic. The populous and low-lying Vietnamese Mekong delta is facing accelerating subsidence rates and effective mitigation strategies are urgently needed to save-guard the future sustainability of the delta. This paper gathers results from existing measurements and estimates of subsidence in the Mekong delta and presents new, delta-wide datasets of PSI observations of vertical velocity from 2014–2019. We describe the practical application of this new data in ongoing projects in Vietnam and outline a planned approach to determine depth-dependent subsidence rates, using this new dataset in combination with field surveys and physics-based numerical models, to advance towards improved quantitation of the contributions of individual subsidence mechanisms.

Beschreibung: Agricultural land use on peatlands inevitably causes ongoing land surface subsidence resulting in a reduction of productivity. In addition, oxidation of the peat substrate associated with subsidence is responsible for greenhouse gas emission with the ensuing consequence for global climatic stability. A concept of “paludiculture”, the utilisation of wet or rewetted peatlands for agriculture, has been proposed in European countries to avoid further subsidence and greenhouse gas emission. However, few studies have documented a long-term record of subsidence through agriculture in wet peatlands such as paddy fields for rice cultivation. In this study, we measured the subsidence rates of peatland in rice paddy use and compared them to the rates in peatland with upland crop cultivation. The average subsidence between 2006 and 2016 for the paddy plots was 3.6±1.9 cm (± SE) and significantly less than that of 25.6±1.7 cm for the upland plots, and the subsidence reduced linearly as the period of paddy use increased. These results suggest that paddy use of peatlands can effectively reduce subsidence. Our results will encourage the use of peatlands with a wet environment as one of the valid options for future peatland management in terms of mitigation of land subsidence and peat loss.

Beschreibung: Widespread thawing of permafrost in the northern Eurasian continent causes severe problems for infrastructure and global climate. We test the potential of Sentinel-1 SAR imagery to enhance detection of permafrost surface changes in the Siberian lowlands of the northern Eurasian continent at the Yamal peninsula site. We used InSAR time-series technique to detect seasonal surface movements related to permafrost active layer changes. The satellite InSAR time-series analysis has detected continuous movements, subsidence in three zones, which have occurred during the time period from 2017 to 2018. Observed subsidence zones show up to 180 mm yr−1 rates of seasonal active layers changes. These seasonal ground displacement patterns align well with lithology and linked to anthropogenic impact on the permafrost surface changes in the area. The results show that Sentinel-1 mission is of great importance for the longer-term monitoring of active layer thickening in permafrost regions. The combined analyses of the obtained InSAR time series with additional field observations may support regular process monitoring as part of a global warming risk assessment.

Beschreibung: Satellite-based InSAR (Interferometric Synthetic Aperture Radar) provides an effective way to measure large-scale land surface motions. Currently, the atmospheric phase delay is one of the most critical issues in InSAR deformation monitoring. Generic Atmospheric Correction Online Service (GACOS) is a free, globally available and easy-to-implement tool to generate high-resolution zenith total delay maps, which could be used for InSAR atmospheric delay correction. The mean velocity could then be estimated by stacking multiple GACOS-corrected interferograms. We applied the proposed GACOS-corrected InSAR stacking method in the North China Plain and analysed its performance. Within the 549 interferograms, more than 85 % gained positive correction performances. The correlation between the phase-dZTD indicator and the performance reached 0.89, demonstrating a significant relationship. Deformation maps revealed by InSAR stacking with and without GACOS corrections showed that GACOS could mainly remove the topography-related and long wavelength signals.

Beschreibung: In the region of Maastricht, both in the Netherlands and in Belgium, about 400 room and pillar mines have been excavated in weak Upper-Cretaceous limestones. Pillar instability has resulted in a number of large-scale collapses and serious surface subsidence with faulting and sinkhole formation. The Heidegroeve used to be a very stable mine for more than 50 years, until pillars started to fracture and spall unexpectedly in the summer of 1987. The collapse of the abandoned mine occurred in June 1988, and was initially detected when faults and sinkholes had formed at the surface. Originally it was postulated that just creep deformation inside this mine was the main cause. However, a stability analysis revealed that all pillars inside the collapse area showed sufficient safety factors and should still be intact, while the weakest part, with several pillars of insufficient strength, had been fractured but is still standing. In the vicinity of the collapse area mines have been excavated at a lower level. Therefore it was postulated that the collapse of the Heidegroeve was related to an unknown and inaccessible continuation of these mine workings underneath. Indeed, recent, rather adventurous fieldwork revealed a downward collapse-induced fault giving access to open galleries and collapse structures about 3.5 m below the Heidegroeve. Inside the collapse area of the Heidegroeve itself, accessible through openings between the debris fragments, severe tilting of gallery floors was observed, which was probably brought about by punching of pillars of the lower mine. This case study with an unusual result shows that great care must always be taken in the analysis of the stability of mines and the assessment of the risk of surface subsidence.

Beschreibung: Pingtung coastal plain, located at the active convergent boundary between Philippine Sea Plate and Eurasian Plate, is one of the most active areas regarding tectonic deformation in Taiwan. Groundwater over-pumping for aquaculture along the coast area of Pingtung plain induced a serious land subsidence problem for decades. How much land subsidence contributed by tectonic activity and groundwater pumping is a crucial issue for tectonic study and groundwater management in this area. This study collected the data in different fields and proposed a conceptual model to calculate the quantities of land subsidence caused by natural (tectonic) and human (pumping) factors. The data from the Global Positioning System (GPS) are used to illustrate the total subsidence concerning vertical displacement. A system called the multi-level compaction monitoring well (MCMW) is able to measure the vertical compaction in different depths from the earth surface to the depth of 200 m. Two GPS stations, named CLON and FALI, close to two MCMWs, named Jiadong and Fangliao, are adopted for analysis The data during 2007 and 2016 taken from MCMWs and groundwater observation wells indicate that the compaction in the shallow depth should be mainly caused by groundwater over-pumping due to their high correlation coefficients (from 0.58–0.95). The difference of the vertical deformation between GPS and MCMW indicates that there is deformation beyond the depth within 200 m. From the data and literature, the further vertical deformation should be due to tectonic activity associated with tectonic escape and extrusion of the Taiwan orogen with average vertical deformation from −3.0 to −4.4 mm. Therefore, the quantities of land subsidence contributed by local groundwater over-pumping and regional tectonic activities are successfully separated. The method and concept proposed in this study can be used in land subsidence quantification due to both tectonic activity and groundwater over-pumping.

Beschreibung: Monitoring of mining areas and associanted dam stability, has become increasingly important as the awareness of safety and environmental protection is rising. An appropriate monitoring scheme is necessitated to legally activate, reactivate, or terminate mining operations. The project Integrated Mining Impact Monitoring (i2Mon) aims to identify and analyze mining-induced impact, in particular its ground deformation. The monitoring system comprises terrestrial measurement and remote sensing: levelling, GPS, LiDAR scanning, UAV survey, and SAR interferometry. For interpretation and prediction, modelling will be used to simulate local displacements by different factors. The final goal is to launch an interactive GIS-based platform as an early warning and decision making system for mining industry. Currently, the project is proceeding from a preparatory phase. This paper focuses on spaceborne SAR interferometry, whereby we can cost-effectively monitor ground movement at millimeter level over a large area. We introduce the prototype of our InSAR monitoring system. The test result from Sentinel-1 images shows the surface movement during 2018 at a deactivating open-pit coal mine in Germany. We discuss the current status, ongoing works, planned test sites in Poland, and how we integrate data from different sensors and approaches.

Beschreibung: The fast railway line B is a high-speed railway passenger passageway in Beijing, with a total length of 40.75 km. In the plain area, the railway passes through the land subsidence area of Beijing from south to north, which poses a certain threat to the normal operation of a high-speed railway. Using layered monitoring data for the period 2009–2014 from station A, this paper analyses dynamic changes in the annual subsidence rate and the rate and percentage of soil deformation at different depths, as well as the compression deformation law of soil with different lithology and depth with the change of the water level. The results show that (1) since 2012, the proportion of shallow-layer (≤82 m) compression and settlement contribution has gradually decreased, while the proportion of deep-layer (〉 82 m) compression has significantly increased; (2) during the deformation process of layered soil, the amount of compression is closely related to the change of groundwater level; and (3) the shallow, middle and deep strata show obvious viscoelastic–plastic deformation characteristics on the whole.

Beschreibung: We have delineated ten years of urban subsidence derived from continuous GPS stations operated by the Crustal Movement Observational Network of China (CMONOC) within and adjacent to the municipality of Tianjin. A method for obtaining accurate site velocities with respect to a stable regional reference frame is described. CMONOC stations in Jizhou (JIXN) and Baodi (TJBD) districts recorded minor subsidence of approximately 1 to 2 mm yr−1 during the period from 2010 to 2019. One station in Wuqing (TJWQ) district and one station in Binhai (TJBH) district recorded steady subsidence of approximately 5 and 2 cm yr−1 from 2010 to 2019, respectively. One station in Cangzhou (HECX) of Hebei Province, adjacent to Tianjin, recorded steady subsidence of approximately 2.4 cm yr−1 during 2010–2014 and more rapid subsidence of 4 cm yr−1 since 2015. TJWQ recorded the most rapid land subsidence and the most significant seasonal ground oscillations (uplift and subsidence) among these five stations. This study indicates that subsidence rates in Tianjin vary significantly in space and time. Particular attention should be paid, therefore, to extrapolate or infer a rate of subsidence for an area on the basis of a subsidence rate obtained from previous GPS observations or proximal GPS sites. The subsidence time series presented in this study provide reliable “ground truth” and constraints for calibrating or validating subsidence estimations from numerical modeling and repeated surveys using other remote sensing techniques, such as Interferometric Synthetic Aperture Radar (InSAR).

Beschreibung: Over 1992–2018, groundwater overexploitation had caused large-scale land subsidence in the Choshui River Alluvial Fan (CRAF) in Taiwan. The Taiwan High Speed Railway (THSR) passes through an area of severe subsidence in CRAF, and the subsidence poses a serious threat to its operation. How to effectively monitor land subsidence here has become a major issue in Taiwan. In this paper, we introduce a multiple-sensor monitoring system for land subsidence, including 50 continuous operation reference stations (CORS), multi temporal InSAR (MT-InSAR), a 1000 km levelling network, 34 multi-layer compaction monitoring wells and 116 groundwater monitoring wells. This system can monitor the extent of land subsidence and provide data for studying the mechanism of land subsidence. We use the Internet of Things (IoT) technology to control and manage the sensors and develop a bigdata processing procedure to analyse the monitoring data for the system of sensors. The procedure makes the land subsidence monitoring more efficient and intelligent.

Beschreibung: With the rapid growth of economy in coastal megacities, the construction of supertall buildings with deep pile foundations adjacent to tunnels in soft soil is inevitable. The additional subsidence of tunnel and long-term subsidence of soft soil was appeared caused by the supertall building load transferred through pile foundation. In this paper, a typical case in Shanghai where deep piles of supertall building group adjacent to a metro tunnel was selected, and the long-term monitoring data of tunnel deformation was collected and analysed. The layered subsidence of surrounding soft soil was analysed by using the monitoring data of extensometers in a land subsidence monitoring station near the study area. The results of data analysis showed that the construction of supertall building had a significant impact on the adjacent tunnel subsidence. Moreover, with the increase of the load transferred from building structure to pile foundation, the adjacent tunnel appeared sustained uneven subsidence. And the subsidence of tunnel in the study area mainly depended on the deformation of underlying soil.

Beschreibung: Amsterdam currently has a huge task of assessing and potentially upgrading its quay walls along the historic canals. Before replacement can take place, Amsterdam needs to determine the potential impact the replacement can have on the nearby buildings. The rate of vertical deformation of the adjacent buildings is used as indicator of potential foundation problems. To determine that rate, the current practice is to monitor the buildings by levelling for two years at least. This study shows that application of satellite measurements using Permanent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) could reduce the monitoring period to a few months. The paper describes the statistical procedure that has been applied to levelling and satellite measurements to verify their reliability and determine the rate of vertical deformation of the buildings. The procedure was applied in three case studies. The rates of deformation observed in the InSAR measurements are in good agreement with the rates of deformation observed in the levelling in two of the case studies. The locally optimized InSAR data set with observations in the period 2014–2019 provides an almost 100 % coverage of reliable data points for all buildings in the case studies. More experience will need to be gained in the interpretation of InSAR measurements with respect to vulnerability of the buildings. Also, the procedure may be extended to include analysis of non-linear trends such as second order trends and seasonal effects.

Beschreibung: The analysis of the vertical movements of the soil in the Po River plane of the Emilia-Romagna Region (Italy) was updated through an interferometric analysis referred to the 2011–2016 time-span. This activity is a continuation of previous studies on the state of knowledge of vertical soil movements in the same area, analyzed firstly by levelling and GNSS and more recently by SAR interferometry for the periods 1992–2000, 2002–2006, 2006–2011, on behalf of the Emilia-Romagna Region. The survey area analysed was approximately 13 300 km2, which corresponds to the territory of the regional plain. The interferometric dataset was calibrated through the use of velocity time series of several permanent GNSS stations. Among the 36 stations analysed, 22 were included in the study area: 16 were used for the calibration and 6 as check points). The velocities required for the calibration of the SAR analysis were calculated in the period following the important seismic events that struck the territory of the Emilia Romagna Region in May 2012. The interferometric analysis was carried out by TRE ALTAMIRA using the SqueeSAR™ technology. In particular, in order to update the interferometric dataset to 2016, it was necessary to perform a joint processing of the available RADARSAT-1 data and of the data acquired by the RADARSAT-2 satellite using a specific operating mode of the SqueeSAR™ algorithm known as stitching; this approach allowed the joint processing of images acquired in the same geometry by these two satellites. The study of the time series of the GNSS permanent stations used to provide the velocity datum to the interferometric analysis, is described, and the results of the SqueeSAR™ interferometric processing are reported. Statistical analyses on the spatial distribution and the type of scatterers have been performed during the screening and validation procedures of the dataset, and for the identification and removal of the outliers. Finally, the resulting map is described in order to analyse the measured soil movements with respect to the results obtained in past analyses, and the possible geological and human-induced causes, which could have produced them.

Beschreibung: Cardona area presents surface rising and subsidence active movements. In 1999 a series of sinkholes appeared due to the infiltration of Cardener River water into the mine tunnels, damaging surface infrastructures. Since then, high precision GNSS/GPS was used annually to position a network of 40 points spread over the area. GNSS/GPS work is carried out with the Fast-Static (FS) method. Additionally the surface movements have been monitored with satellite Differential Interferometry Synthetic Aperture Radar (DInSAR). Results indicate that the movement has a complex spatial distribution although consistent along time. Some areas show surface rising during the last two decades, while other areas show subsidence. The use of the two techniques allowed to determine the most plausible causes of these movements generated by a set of interwoven natural and human-induced complex processes.

Beschreibung: The backbone of the Amsterdam Ordnance Datum (NAP) is a network of about 400 primary subsurface markers. Relative movements between the primary subsurface markers are measured with spirit levelling once in 10–20 years. However, little is known about absolute vertical movements of the primary network. This information is indispensable for the interpretation of water level measurements at the tide gauges along the Dutch coast. It may be provided by gravity measurements. Here we present a time-series analysis of more than twenty years of gravity measurements at the stations Westerbork, Epen, Zundert, and Radio Kootwijk. It reveals that only station Epen shows a statistically significant movement of -0.252±0.066 µGal yr−1, which corresponds to an uplift of 1.3±0.5 mm yr−1. For the other stations, the trends are statistically not different from zero at a significance level of 0.05. Corrections for water table variations are found to be indispensable; peak-to-peak amplitudes range from 4 µGal (Westerbork) to 28 µGal (Radio Kootwijk). Depsite some fundamental objections, corrections for instrumental offsets reduce the data scatter. First experiments with 7 years of soil moisture data acquired at station Radio Kootwijk reveal that the gravity signal of soil moisture variations has a standard deviation of 2.2 µGal, which is comparable to the noise standard deviation of measured gravity.

Beschreibung: A previous study of the Ca Mau province in Vietnam (Karlsrud et al., 2017a) suggested that ongoing groundwater pumping, which by 2012 had caused a drawdown of the water level in aquifers of up to 20 m, caused subsidence of the order 2–4 cm yr−1, and could have reached over 40 cm already. Earlier InSAR studies also suggested ongoing subsidence rates of that order. If the groundwater pumping continues, the total subsidence could reach well over 1 m within the next few decades. The predicted climate driven sea level rise, to be of the order of 60 cm by 2100, will further add to the severe effect of the subsidence. As most of the Ca Mau province lies only 0.5 to 1.5 m a.s.l. (above sea level), the consequences would rapidly become very serious for the livelihood of people in the region. Increased saltwater intrusion into canals and tributaries in the province, and beginning salination of some of the aquifers from which groundwater is pumped, is already observed. In 2017, for the first time, a physical system for subsidence monitoring was installed at three selected locations in the Ca Mau province. At each location a deep benchmark to a depth of 100 m was installed, each with 3 piezometers at depths ranging from 15 to 60 m. An InSAR corner reflector was also installed at each site. The paper presents data collected from these new monitoring stations up until the middle 2019. When including estimated subsidence stemming from the soil levels deeper than 100 m, the total present rate of subsidence at the three new monitoring stations range from 17 to 44 mm yr−1. New and previous data show an almost linear decrease in water level within the aquifers from which groundwater is pumped. The data show some seasonal variations in subsidence rates, which is also reflected in variations in pore pressures in the sediments. Such variations are probably related to seasonal variations in levels of groundwater pumping. It is feared that many of the other provinces south of Ho Chi Minh city, face similar subsidence problems. The monitoring program should be extended to verify that. Measures to reduce groundwater and subsidence are urgently needed.

Beschreibung: Land subsidence caused by large-scale engineering construction may damage the surrounding infrastructures and cause huge economic losses in inner-city environments. In this study, we used PS-InSAR technology on 68 TerraSAR-X images to acquire deformation in the Beijing Plain between February 2010 and December 2018. Then, we calculated the additional stress derived from building loads using the method proposed by Boussinesq in the Central Business District (CBD). We found that the depth of influence of additional stresses induced by building loads was 80 m and that spatial distribution pattern of the land subsidence rate agreed well with the additional stress. We found that the influence range of ground subsidence caused by metro construction is 200 m at Ciqikou station by analyzing the subsidence rate profile perpendicular to subway line No. 7 and that the maximum land subsidence rate is 23.2 mm yr−1. Time series analysis of PS around Ciqikou station shows that land subsidence caused by excavation activities mainly occurs in the period of metro construction. Ground deformation rate decreases gradually after 372 d of subway operation. The results of both cases show that large-scale engineering construction will lead to significant land subsidence which should be considered in future urbanization.

Beschreibung: Relative sea-level rise (RSLR), i.e. sea-level rise due to climate changes combined with land subsidence, is one of the processes that is most severely threatening the coastal systems around the world. The Venice coastland forms the major low-lying area in Italy and encompasses a variety of environments, such as farmlands, estuaries, deltas, lagoons and urbanized areas. Valuable ecosystems, historical heritages and economic activities are located in this area. Since most of the territory lies at a ground elevation below or slightly above the mean sea-level, also a few mm yr−1 of land subsidence can seriously impacts on the Venice coastal system. In this study, we present an analysis of the vulnerability to RSLR considering an uneven land subsidence distribution, with an application on the Venice coastland. The analysis is delineated at the regional scale by an index-based model and a proper coupling of various thematic layers, such as high spatial resolution land subsidence data retrieved by satellite SAR interferometry, ongoing and projected sea-level rise trends, and morpho-physiographic setting of the coastland.

Beschreibung: Land subsidence in the Netherlands, mainly occurring in its western and northern peat and clay soils, causes significant damage to houses and infrastructure, estimated at EUR 17 billion until 2050, through differential settlement of shallow foundations, negative skin friction and fungal decay of timber piles. Various studies and reports both in The Netherlands and abroad have addressed the potential economic impacts of subsidence on houses: yet, these studies lack spatially detailed data and instead rely on generic assumptions on expected damage restoration costs. By using a hedonic pricing model, this study examines the impact of subsidence on housing prices in the Dutch cities of Rotterdam and Gouda. In contrast to earlier studies, subsidence and its impact on property values are examined at house level. We test for the effect of subsidence with data related to (i) general (uniform) subsidence (mm yr−1), (ii) differential subsidence of a building and (iii) subsidence of the surrounding area in relation to the house. Results show that uniform subsidence has the largest impact on property values with approximately −6 %, while “differential” and “surrounding” subsidence show respectively −2 % and no effect. These results could prove useful to policymakers, homeowners and housing corporations by generating a better understanding of the impact of subsidence on property values and subsequently to create awareness and spur investments in measures to mitigate damage. It should be noted that these results are specific to the research area are therefore not immediately scalable to other cities as local conditions differ.

Beschreibung: Groundwater has been a major source of agricultural, municipal, and domestic water supply since the early 1920s in the Coachella Valley, California, USA. Land subsidence, resulting from aquifer-system compaction and groundwater-level declines, has been a concern of the Coachella Valley Water District (CVWD) since the mid-1990s. As a result, the CVWD has implemented several projects to address groundwater overdraft that fall under three categories – groundwater substitution, conservation, and managed aquifer-recharge (MAR). The implementation of three projects in particular – replacing groundwater extraction with surface water from the Colorado River and recycled water (Mid-Valley Pipeline project), reducing water usage by tiered-rate costs, and increasing groundwater recharge at the Thomas E. Levy Groundwater Replenishment Facility – are potentially linked to markedly improved groundwater levels and subsidence conditions, including in some of the historically most overdrafted areas in the southern Coachella Valley. Groundwater-level and subsidence monitoring have tracked the effect these projects have had on the aquifer system. Prior to about 2010, water levels persistently declined, and some had reached historically low levels by 2010. Since about 2010, however, groundwater levels have stabilized or partially recovered, and subsidence has stopped or slowed substantially almost everywhere it previously had been observed; uplift was observed in some areas. Furthermore, results of Interferometric Synthetic Aperture Radar analyses for 1995–2017 indicate that as much as about 0.6 m of subsidence occurred; nearly all of which occurred prior to 2010. Continued monitoring of water levels and subsidence is necessary to inform the CVWD about future mitigation measures. The water management strategies implemented by the CVWD can inform managers of other overdrafted and subsidence-prone basins as they seek solutions to reduce overdraft and subsidence.

Beschreibung: Subsidence can result from the collapse of underground cavities. The impact of the movements on existing structures and infrastructures is generally dramatic. Geosynthetic sheets (RG) can be used to reduce their impact. This paper focuses on the use of large-scale physical modelling to study the subsidence mechanisms and to estimate the RG efficiency for cohesive or granular soil layers. The results have shown that the RG reduced the ground movement even under important overload. The deformation of the RG and the surface settlement depend both on the soil type and overload intensity. The experimental results are compared to analytical solutions proposed to design the RG for cohesive and granular soils. Stress distribution on the RG was investigated. The analytical and experimental results are rather similar, that shows the relevance of the analytical models to predict the behaviour of reinforced soil layers.

Beschreibung: Water authorities responsible for water quantity and water quality management may strongly influence the magnitude of greenhouse gas emissions from the surface waters and the adjacent peat areas within their territories. Climate smart water management (reducing influx of organic matter and improving water quality) is therefore a potentially strong mitigation tool. We hypothesize that climate smart water management has a stronger mitigation potential than reducing emissions from the operational management of a Water Authority. Based on literature data on greenhouse gas emissions from ditches and agricultural peatlands, we present a case study of a Dutch Water Authority – Amstel, Gooi and Vecht (operated by Waternet). We estimate that greenhouse gas emissions from the 195 km2 large peat area within its territory are 470 kt CO2-eq per year. An additional 231 kt CO2-eq yr−1 is emitted from the water bodies within the 102 km2 large water area territory. Both emissions are considerably higher than the estimated climate footprint of the operational management of the water board (∼62 kt CO2-eq per year in 2017). While Waternet strives to have a net zero emission of greenhouse gases related to its operational management by 2020, we postulate that measures (to be taken before 2030) such as the prevention of organic matter and nutrients entering surface waters, the removal of organic carbon from ditches and higher groundwater levels in agricultural peatlands, may reduce greenhouse gas emissions in ditches and agricultural peat meadows with 26 and 27 kt CO2-eq per year, respectively. Measures that are taken to reduce greenhouse gas emissions in water bodies are expected to have a positive impact on water quality as well.

Beschreibung: Two earth fissures appeared in Murcia province (southeastern Spain) after the flood occurred because of a heavy downpour on 28 September 2012. In this area, located within the Guadalentín Valley, up to 212 L m−2 was reported that day. More than 200 agricultural exploitations were destroyed by the flooding, with a devastating effect on many infrastructures, such as a main A-7 highway bridge that collapsed in this event. The earth fissures appeared after this flooding in the towns of Puerto Lumbreras and Totana. The first fissure showed a straight-line direction approximately parallel to the main geological structures of the Guadalentín Valley. The total length of the fissure was 400 m and was 2 to 3 m in depth. The soil in the fissure is classified as a low-plasticity silt with some sand and clay, ML, according to the Unified Soil Classification System. From the sieve and hydrometer tests, the percentage of silt in these samples was between 48 % and 68 %, the clay content between 12 % and 30 % and the sand content between 2 % and 40 %. The plasticity index was smaller than 9.2 for all the samples. To evaluate the piping and internal erosion susceptibility of the soil, pinhole, crumb and geochemical tests were done on the collected samples. A result of non-dispersive soil was obtained from crumb and pinhole tests. Nevertheless, the pH, sodium adsorption ratio and exchangeable sodium percentage tests showed that some samples could be affected by the dispersion of the soil. Also, the collapsible potential of the soil was studied, showing negative results for all the samples except for that collected at the southern end of the fissure, which showed a medium to high potential. Concerning the Totana fissure, it appeared with different branches and holes instead of as a rectilinear pattern. The total length of the fissure was 190 m, with the soil characterized as a silty soil. Lastly, INSAR data, GPS, GPR and land subsidence maps were used to study the possible origin of these fissures.

Beschreibung: Though global awareness of land subsidence has increased over recent years, subsidence remains an ongoing and largely unsolved problem, which is exemplified by frequent discoveries of apparently new subsiding areas. This means that for many of these areas there is a continuous and growing need to provide guidance to decision makers on how to tackle this global problem. This paper presents a comprehensive, step-by-step approach to address land subsidence, illustrated by best practise examples from around the world. The approach places emphasis on the long-term sustainability of resources, whose development is related to the subsidence problems. We identified 6 steps, collectively referred to as the 6M approach, that are crucial to tackle subsidence: Measuring, understanding Mechanisms, Modelling, Money, Measures and Monitoring. This paper offers guidance for implementing the 6M approach, and the lessons learned from the real-life examples provide valuable information and inspiration for decision makers and experts to address subsidence. The focus is on subsidence in deltaic and coastal areas where subsidence contributes to relative sea level rise. It is expected that the 6M approach will contribute to lowering the threshold to act on subsidence. The 6M approach is also used as a guiding principle for the thematic subdivision of TISOLS, providing a meaningful linkage between subsidence science and the societal response to subsidence problems.

Beschreibung: This study was undertaken in order to accurately analyze the land subsidence that is caused by the change in the seepage and stress fields during the pumping and recharge of groundwater. Based on Biot's consolidation theory and groundwater seepage theory (combined with theory regarding the nonlinear rheology of soil), the constitutive relationship of soil was extended to viscoelastic plastic; concurrently, considering the dynamic changes in hydraulic parameters and soil mechanical parameters, a three-dimensional fully coupled model of groundwater seepage and soil deformation was established. Using the groundwater recycling pumping and recharge test conducted by Land Subsidence Monitoring and Early Warning Center in Cangzhou City as an example, the site was divided into four loose porous aquifers. A constantly circulating pumping–recharge flow was simulated numerically, and numerical simulation was carried out on the third and fourth confined aquifers. The influence of groundwater seepage on soil deformation was analyzed, and the variation in hydraulic parameters and soil mechanical parameters were studied under the influence of the abovementioned cyclic pumping and recharge. The results show that soil deformation lags behind the change in the groundwater level, and that permanent residual deformation of soil is produced by water level fluctuations during groundwater pumping–recharge cycles. The effective porosity, the permeability coefficient and the Poisson ratio are positively correlated with the water level fluctuation in groundwater pumping–recharge cycles, whereas the modulus of deformation is negatively correlated with the water level fluctuation in groundwater during this process. All parameters change, and this change is permanent. The simulated results are in good agreement with the measured values.

Beschreibung: The Netherlands is subject to anthropogenically induced deep-source and shallow subsidence. Deep sources are related to the extraction of hydrocarbons or salt mining activities, whereas shallow subsidence comprise compaction, shrinkage and oxidation of clay and peat under progressive lowering groundwater levels. At TNO – Geological Survey of the Netherlands, deep-source and shallow subsidence are presently investigated separately. Forward and inverse modelling techniques are generally deployed to forecast subsidence caused by deep sources, whereas shallow subsidence is predicted using the high-resolution geological 3-D subsurface model GeoTOP. A new approach is proposed which encompasses forward and inverse modelling techniques and GeoTOP. Such combination will yield a powerful shallow subsidence forecasting model, which would be a critical step forward in analyzing shallow subsidence in the Netherlands on a regional scale. In the present contribution, we sketch the setup of this new approach that combines subsidence measurements, GeoTOP subsurface data, and data assimilation of subsidence with the help of state-of-the-art forward and inverse modelling techniques. The setup uses ensemble technology to catch uncertainties of parameters, different model choices, and implicit correlations. With such a setup, forecasts can be faithfully accompanied with a quality measure that enables to judge its relevance and confidence range.

Beschreibung: Climatic conditions and vegetation cover influence water flux in a slope which affect the pore water pressure and self weight, hence its stability. High evapotranspiration and low precipitation rates during summer cause dry soil with low soil moisture (SM) that leads to soil shrinkage, which leads to cracking and reduced shear strength, which consequently decreases the stability of slopes. Soil re-wetting increases slope weight and exerts an additional driving force on the slope. Using Earth observation (EO) data facilitates frequent, large-scale monitoring to identify the vulnerable areas along the slopes to avoid instability. Here we study the displacement of a vegetated dike subject to SM variations under varying climatic conditions. Results show that the SM and magnitude of total displacement at a desired location are highly positively correlated without time lag. This proof-of-concept study shows that near surface displacement due to interaction with the atmosphere has a strong relation with the water availability in the slope and therefore the Factor of Safety (FoS).

Beschreibung: From the analysis of GPS monitoring data collected above gas fields in the Adriatic Sea, in a few cases subsidence responses have been observed not to directly correlate with the production trend. Such behavior, already described in the literature, may be due to several physical phenomena, ranging from simple delayed aquifer depletion to a much more complex time-dependent mechanical response of subsurface geomaterials to fluid withdrawal. In order to accurately reproduce it and therefore to be able to provide reliable forecasts, in the last years Eni has enriched its 3D finite element geomechanical modeling workflow by adopting an advanced constitutive model (Vermeer and Neher, 1999), which also considers the viscous component of the deformation. While the numerical implementation of such methodology has already been validated at laboratory scale and tested on synthetic hydrocarbon fields, the work herein presents its first application to a real gas field in the Adriatic Sea where the phenomenon has been observed. The results show that the model is capable to reproduce very accurately both GPS data and other available measurements. It is worth remarking that initial runs, characterized by the use of model parameter values directly obtained from the interpretation of mechanical laboratory tests, already provided very good results and only minor tuning operations have been required to perfect the model outcomes. Ongoing R&D projects are focused on a regional scale characterization of the Adriatic Sea basin in the framework of the Vermeer and Neher model approach.

Beschreibung: Local and regional governments in The Netherlands are increasingly faced with the question how to adjust and optimize groundwater table conditions in urban areas to minimize ongoing subsidence and its consequences. To help addressing this question, a model was developed that includes soft-soil deformation by creep. In this paper, a study is presented in which the model was used to investigate and intercompare the effectiveness of measures that (a) prevent anomalous water table drop during a drought, (b) suppress the seasonal variability of the water table, and (c) involve a permanent rise of the mean water table.

Beschreibung: Regional subsidence due to fluid depletion includes the interaction among multiple physical processes. Specifically, rock compaction is governed by coupled hydro-mechanical feedbacks involving fluid flow, effective stress change and pore collapse. Although poroelastic models are often used to explain the delay between depletion and subsidence, recent evidence indicates that inelastic effects could alter the rock microstructure, thus exacerbating coupling effects. Here, a constitutive law built within the framework of Breakage Mechanics is proposed to account for the inherent connection between rock microstructure, hydraulic conductivity, and pore compaction. Furthermore, it is embedded into a 1-D hydromechanical coupled finite element analysis (FEA) to explore the effects of micro-structure rearrangement on the development of reservoir compaction. Numerical examples with the proposed model are compared with simulations under constant hydraulic conductivity to illustrate the model capability to capture the non-linear processes of reservoir compaction induced by fluid depletion.

Beschreibung: Interpretation of land subsidence time-series to understand the evolution of the phenomenon and the existing relationships between triggers and measured displacements is a great challenge. Continuous wavelet transform (CWT) is a powerful signal processing method mainly suitable for the analysis of individual nonstationary time-series. CWT expands time-series into the time-frequency space allowing identification of localized nonstationary periodicities. Complementarily, Cross Wavelet Transform (XWT) and Wavelet Coherence (WTC) methods allow the comparison of two time-series that may be expected to be related in order to identify regions in the time-frequency domain that exhibit large common cross-power and wavelet coherence, respectively, and therefore are evocative of causality. In this work we use CWT, XWT and WTC to analyze piezometric and InSAR (interferometric synthetic aperture radar) time-series from the Tertiary aquifer of Madrid (Spain) to illustrate their capabilities for interpreting land subsidence and piezometric time-series information.

Beschreibung: Multiple processes contributing to natural land subsidence in a shallow coastal aquifer near Ravenna (Italy) were identified by analysing the relationships among different data set time series (water table level, rainfall, land reclamation drainage, sea level, etc.) and establishing the correlations with vertical ground motion observed at a high-resolution settlement gauge. Our study highlights the presence of three deformation components related to different processes controlling land subsidence: elastic, delayed-elastic, and irreversible (plastic) components. The elastic and delayed-elastic components are closely related to water table fluctuations that change the effective stress in two portions of the coastal aquifer at a daily (in the sandy unconfined portion) and seasonal time scales (in the layered clay-rich semi-confined prodelta portion), respectively. The irreversible component represents the trend in the land subsidence time series and is due to primary consolidation (pore pressure dissipation) of the fine-grained prodelta levels above where the settlement gauge is located. The amplitudes of the elastic component can be up to 0.2–0.3 mm whereas the amplitude of the delayed-elastic component reaches 0.89 mm. The primary consolidation rate of deformation is 0.9 mm yr−1 and constrains the likely age of prodelta sediments deposition to 1300–2800 years before present. The delayed-elastic subsidence rate has similar magnitude to that due to primary consolidation and is connected to poroelastic effects in the prodelta sequence following seasonal variations in water table. Our findings are important for planning land subsidence management and monitoring strategies especially where the surface aquifer structure is heterogeneous due to different depositional settings. The natural land subsidence rate in the Holocene sediments of the shallow coastal aquifer of Ravenna (North eastern Italy) that we measured in this study accounts for 10 %–20 % of the total current land subsidence rate observed in this portion of Ravenna coastal area (10–20 mm yr−1).

Beschreibung: The Dutch height system, called Normaal Amsterdams Peil (NAP), is realized purely trough leveling between designated benchmarks. In a cycle of 10 years secondary NAP benchmarks, generally located in buildings and civil engineering structures, are surveyed to provide actual and reliable heights. However, leveling campaigns are very labor-intensive and take a lot a of time, resulting in high costs. Furthermore, the planning of secondary leveling is based on limited prior knowledge. Instead of yearly leveling of each bench mark within a region, the strategy could be optimized such that deforming areas are visited more often and stable areas less. Trends estimated from historical NAP data could be used, but these provide insufficient information about stability and reliability of published heights. Therefore we propose to use a nationwide deformation map derived from InSAR satellite data to optimize the planning of the secondary leveling campaigns. By using InSAR deformations combined with information of the NAP benchmarks such as measurement date, type and location, a planning tool has been developed. The first targeted leveling of NAP benchmarks using this tool is planned for 2020.

Beschreibung: In this work, an innovative methodology to generate the automatic ground motion areas mapping is presented. The methodology is based on the analysis of the Synthetic Aperture Radar (SAR)-based displacement time series. The procedure includes two modules developed using the ModelBuilder tool (ArcGis). These modules allow to identify the ground motion areas (GMA) using only one dataset and the persistent GMA (PGMA) considering the different monitored periods and datasets. These areas represent clusters of targets characterized by the same displacement time series trend. The procedure was tested using different sensors such as ERS-1/2, ENVISAT, COSMO-SkyMed and Sentinel-1 covering the periods, 1992–2000, 2003–2010, 2012–2016 and 2014–2017, respectively, over an area of about 500 km2 in the Venetian-Friulian coastal Plain (NE Italy). The resulting mapping allows to detect priority areas where to address further in situ investigations such as to verify the presence of localized buried landforms.

Beschreibung: The assessment of the impact of mining-induced seismicity on the natural environment and infrastructure is often limited to the analysis of terrain surface vibrations. However, similar seismic phenomena, like earthquakes, may also imply dislocations and deformations of the rock mass. Such ground movements may occur in areas which are not directly under the influence of the mining. The study of the displacement field caused by mining-induced seismicity is usually carried out with the use of geodetic methods. Classical geodetic measurements provide discrete information about observed ground movements. As a result, they generally do not provide spatially and temporally relevant estimates of the total range and values of ground movements for specific periods of interest. Moreover, mining-induced seismicity causes a severe threat to buildings. That is why, regarding the complexity of the mechanism of occurrence of mining-induced seismicity and their impact on ground movements, this problem remains a substantial research issue. The presented research aimed to analyse the ground movements caused by mining-induced seismicity. The ground displacements were established based on data from Sentinel-1 satellites applying differential interferometric synthetic aperture radar (DInSAR). The results of the investigation in the copper mining area of the Lower Silesia region of Poland revealed that the observed subsidence caused by mining-induced seismicity usually has a shape of a regular ellipse. The radius of these ground movements does not exceed approximately 2–3 km from the mining-induced tremor's epicenter, and the total subsidence reaches ca. 10–20 cm. More than 50 % of the total subsidence is observed on the surface within a few days after the mining tremor occurrence. Furthermore, the deformations of the surface occur when the energy of mining-induced tremor reaches values of the order of 105 J or higher. The presented research can contribute to better identification and evaluation of the mechanism of the rock mass deformation process caused by mining-induced seismicity. In addition, the use of satellite radar interferometry improves the quality of monitoring of these dynamic phenomena significantly. The data retrieved using this method allow for quasi-continuous monitoring of the local subsidence bowls caused by mining-induced seismicity.

Beschreibung: Land subsidence is an anthropogenic hazard triggered by different causes, one of them is groundwater overexploitation over aquifer systems composed for granular compressible sedimentary fill. One of the effects of this phenomenon is the generation and reactivation of ground failures, becoming risk points for aquifer pollution through the fast infiltration of contaminated water. A system of failures and fractures has developed in the Aguascalientes valley since 1980's when groundwater overexploitation became intensive. Currently, the entire valley present regional subsidence and several ground failures have developed; many of them crossing surficial water flows and sewage pipes, thus, inducing filtering of domestic wastewater to the subsoil and increasing the environmental hazard for the aquifer system. In this work, we present the results of a study to assess the surficial water infiltrations through a subsidence related ground failure crossing a small stream, which carries domestic wastewater. Additionally, we investigate the acquisition method of Electrical Resistivity Tomography (ERT) and the electrode placement more suitable to detect the flow of contaminated water through the studied ground failure. To find out the potential leakage, we use electric geophysical methods, applying Schlumberger, Wenner and dipole-dipole arrangements with electrode separations from 2.5 to 10 m in order to explore a depth from 9 to 30 m. The obtained results showed that the Schlumberger configuration appears to be more helpful to detect changes in the stratigraphy toward depth, while dipole-dipole and Wenner are more suitable to detect lateral variations such as the vertical wastewater leakage in the first 6 to 8 m depth. Resulted resistivity models showed that in the first 10 m depth, the contaminant flow follow with a vertical path through the ground failure, then, the it becomes horizontal, flowing through the more permeable soil strata. Therefore, for the studied sites, the filtration of domestic wastewater through ground failure does not represent an immediate hazard to the aquifer system. Nevertheless, ground failures crossing damaged wastewater pipes or contaminated surficial water flows in Aguascalientes Valley, could induce the infiltration of polluted water to the near surface strata, favoring a potential aquifer pollution in a long term.

Beschreibung: In shield tunnel boring machine constructions, backfill pressure affects surface settlement and the stability of other underground structures nearby. Therefore, it is essential to pre-calculate backfill pressure in the design stage. This study examines and compares the seven internationally known backfill pressure calculation theories and calculates and analyzes the backfill pressures in six virtual ground conditions. The calculated backfill pressure increased as the ground cover increased, but the increase rate decreased. Also, this study performs a numerical analysis to identify the impact on ground settlement and tunnel crown settlement. In the end, settlement was more impacted by face pressure than backfill pressure in the unsaturated and saturated ground conditions. Also, as the ground cover increased, the impact of backfill pressure decreased, and as the applied face pressure decreased, the impact of backfill pressure increased.

Beschreibung: Land subsidence is a worldwide geohazard caused by various factors, and its direct impact is loss of elevation, which is especially severe in coastal areas due to sea level rise. Quantifying contributions of compressed strata is significant for evaluating the subsidence. In this paper, we used distributed fiber optic sensing (DFOS) with Brillouin scattering to monitor the strain distribution along optical cables embedded in a borehole located in Tianjin, China. The novel technique revealed that the land subsidence rate was 21.2 mm a−1 from 2017 to 2019. The strata contributed to the subsidence have been identified in the range of 3 to 35 m. The results showed good agreement with those obtained by a group of extensometers. We demonstrated that DFOS could be a supplement to land subsidence monitoring technologies in coastal areas.

Beschreibung: The use of numerical models for land subsidence prediction above producing hydrocarbon reservoirs has become a common and well-established practice since the early '90s. Usually, uncertainties in the deep rock behavior, which can affect the forecast capability of the models, have been taken into account by running multiple simulations with different constitutive laws and mechanical properties. Then, the most uncertain parameters were calibrated to reproduce available subsidence measurements. The objective of this work is to propose a novel methodological approach for land subsidence prediction and uncertainty quantification by integrating the available monitoring information in numerical models using ad hoc Data Assimilation techniques. The proposed approach allows to: (i) train the model with the available data and improve its accuracy as new information comes in, (ii) quantify the prediction uncertainty by providing confidence intervals and probability measures instead of deterministic outcomes, and (iii) identify the most appropriate rock constitutive model and geomechanical parameters. The methodology is tested in synthetic models of production from hydrocarbon reservoirs. The numerical experiments show that the proposed approach is a promising way to improve the effectiveness and reliability of land subsidence models.

Beschreibung: Understanding the causes and mechanisms of land subsidence is crucial, especially in densely populated coastal plains. In this work, we calculated subsidence rates (SR) in the Po coastal plain, averaged over the last 5.6 and 120 kyr, providing information about land movements on intermediate (103–105 years) time scales. The calculation of SR relied upon core-based correlation of two lagoon horizons over tens of km. Subsidence in the last 120 kyr appears to be controlled mainly by the location of buried tectonic structures, which in turn controlled sedimentation rates and location of highly compressible depositional facies. Numerical modelling shows that subsidence in the last 5.6 kyr is mainly due to compaction of the Late Pleistocene and Holocene deposits (uppermost 30 m).

Beschreibung: Land subsidence caused by overexploitation of aquifers manifests with an increasing frequency in several regions of Greece. The first signs of land subsidence have been identified since 1965 at the west side of Thessaloniki (broader Kalochori village region), in the form of a progressive marine invasion. Since then several areas have been investigated and proved to be affected mainly by the overexploitation of the aquifers. The Multidisciplinary nature of the subsidence mechanism combining the geological, hydrogeological and morphological setting of the areas with the human activities and the land use data makes their study complicated and require the intervention of multiple scientific specialties. Furthermore, at several sites, beside ground truth data, the land subsidence trends and extends have been also identified via multi-temporal InSAR techniques, such as PSI and SBAS techniques. Among the sites to be presented in the current paper is the wider area of Kalochori village in the eastern part of Thessaloniki plain, the east and west Thessaly plain in central Greece and the region extending to the west–southwest of the Amyntaio opencast coalmine in West Macedonia.

Beschreibung: Our association plans to construct in situ formation deformation monitoring wells for shallow formation. In the pilot test, production and injection will be conducted to make the formation deform. Based on the result of the pilot test, we will investigate whether the compaction behavior was perfectly elastic or not. In addition, we plan to conduct coring and core tests to obtain rock properties. In the future, we would like to select the suitable constitutive equation for this gas field based on the obtained data and construct a prediction methodology to control subsidence. Once the land subsidence control technology is established in this study, it is expected that reservoir management for production will be performed.

Beschreibung: Over the past decade, several coastal communities in southeast Florida have experienced a significant increase in flooding frequency, which has caused significant disturbance to property, commerce, and overall quality of life. The increased flooding frequency reflects the contribution of global, regional, and local processes that affect elevation difference between coastal communities and rising sea level. In a recent project, funded by the state of Florida, we monitor coastal subsidence in southeast Florida using GPS and InSAR observations, in order to evaluate the contribution of local subsidence to the increased coastal flooding hazard. Preliminary results reveal that subsidence occurs in localized patches (

Beschreibung: The paper discuses one of the most complicated cases in tunnel construction practice in the water-saturated fine-grained deposits in Moscow. Due to the imperfectness of enclosing engineering structures, groundwater and water-saturated soils broke through to the tunnel at the time of its construction. This resulted in the formation of decompaction zones in the enclosing ground massif as well as in deformation of buildings and land surface subsidence. After the end of construction, settling of land surface near tunnel has almost stopped; however, groundwater seepage to the tunnel still continues despite numerous percolation-control measures. As a result, the decision was made to arrange the permanently operating drainage, which could have sustain the groundwater level at the required depth. The possible settling of the land surface has been calculated for the area near the tunnel due to the soil compaction upon the water drawdown. The calculation is based on the principle of linear deformability of soils and on the Terzaghi law about the stresses of two kinds in a ground massif. The results obtained prove that the settlement values will not exceed the critical values adopted by standard regulatory documents. It appears virtually impossible to take account in calculations the transformation of ground massif parameters at the sites of soil breakthrough to the tunnel. Therefore, it is necessary to keep continuous observations over the deformation of buildings and the land subsidence in the tunnel zone. Monitoring and permanent drainage should ensure the safe operation of the tunnel.

Beschreibung: The fate of coastal marshlands in the near future will strongly depend on their capability to maintain their elevation above a rising mean sea level. Together with the deposition of inorganic sediments during high tides, organic soil production by halophytic vegetation, and organic matter decomposition, land subsidence due to natural soil compression is a major factor controlling the actual elevation of salt-marsh platforms. Due to their high porosity and compressibility, the marsh sedimentary body undergoes large compression because of the load of overlying more recent deposits. The characterization of the geotechnical properties of these deposits is therefore of paramount importance to quantify consolidation versus accretion and relative sea level rise. However, undisturbed sampling of this loose material is extremely challenging and lab tests on in-situ collected samples are not properly representative of in-situ conditions due to the scale effects in highly heterogeneous silty soils such as those of the Venice lagoon. To overcome this limitation, an in-situ loading test was carried out in the Lazzaretto Nuovo salt-marsh in the Venice Lagoon, Italy. The load is obtained by a number of plastic tanks that are filled with seawater, reaching a cumulative load of 40 kN applied on a 2.5×1.8 m2 surface. Specific instrumentations were deployed before positioning the tanks to measure soil vertical displacement at various depths below the load (0, 10, and 50 cm) and distances (0, 40, and 80 cm) from the load centre. Moreover, six pressure transducers were used to record overpressure dissipation over time. The collected datasets will be interpreted through a 3-D flow-deformation model that, once calibrated, provides reliable estimates of the compressibility values for each monitored depth interval.

Beschreibung: Land subsidence, as a surface response to the development, utilization and evolution of underground space, has become a global and multidisciplinary complex geological environment problem. Since the 1960s, land subsidence has been developing rapidly in the Beijing Plain area. Against the backdrop of the integration of Beijing, Tianjin and Hebei in addition to “southern water” (South-to-North Water Diversion Project, SNWDP) entering Beijing, the systematic study of the evolution mechanism of land subsidence is of great significance for the sustainable development of the regional economy. Firstly, this study used ENVISAT ASAR and RADARSAT-2 data to obtain surface deformation information for the Beijing Plain area from 2004 to 2015 and then verified the results. Secondly, the study area was divided into units using a 960 m×960 m grid, and the ground settlement rate of each grid unit from 2004 to 2015 was obtained. Finally, the Mann–Kendall test was performed on the grid to obtain the mutation information for each grid unit. Combined with hydrogeology and basic geological conditions, we have attempted to analyze the causes of the mutations in the grid. The results show that 2347 grid cells were mutated in a single year, with most of these distributed across the Yongding River alluvial fan and the middle and lower parts of the Chaobai River alluvial fan. A total of 1128 grid cells were mutated in multiple years, with the majority of these cells mainly distributed across the upper-middle area of the alluvial fan, near the emergency water source and at the edge of the groundwater funnel. This study aims to provide favorable technical support and a scientific basis for urban construction in Beijing.

Beschreibung: In the coal mining districts of the Netherlands, Belgium and Germany, we identified 662 previously unidentified depressions at the land surface using LIDAR data. Their density decreases westwards along with deepening of the Carboniferous coal layers, while not changing in dimensions. The timing of their formation based on historical maps and landowner reports, suggests that they mostly formed during the period 1920–1970, the peak of mining activity. Based on their position, density and age, we link the formation of depressions to the coal-mining activities in South Limburg, Germany and Belgium. Our working hypothesis tentatively explains the origin, mechanism of formation and timing of these local subsidence features.

Beschreibung: Coastal subsidence owing to compaction of Holocene strata and deeper-rooted components affects large delta plains such as the Tabasco delta in southern Mexico (Gulf coast). For this system, GNSS3-PPP ground-truthed LiDAR imagery of high-resolution dated beach-ridge series reveals considerable differential subsidence on either side of the present Usumacinta-Grijalva River mouth. Collected field-data allows for quantification of differential subsidence over several time windows and reconstruction of relative sea-level rise back to 5000 years ago. Observed differential subsidence of 1–1.5 m is regarded to be syn-sedimentary delta-subsurface compaction of buried strata in response to the accumulating overburden of the prograding beach-ridge complex.

Beschreibung: Land subsidence affects highly developed urban areas in central Mexico, where inhabitants rely on groundwater for about 60 % of water supply and most of the cities are located in volcanic valleys filled with fine and coarse grained sediments. Compaction associated to groundwater depletion in areas with subsoil contacts sediments-rock have caused differential subsidence, ground fracturing and eventually the reactivation of pre-existing faults, depending on the local geological setting. Remote sensing monitoring methods of land deformation have proved to be useful tools to assess this geological hazard for urban planning. We used L-band ScanSAR data from the ALOS-2 PALSAR-2 mission to produce a regional land subsidence map over an area of about 350 km × 350 km over central Mexico. Our results indicate with a remarkable spatial coverage widespread land subsidence over the major cities, which is ranging from more than 30 cm yr−1 in Mexico City to 5–10 cm yr−1 in other locations.

Beschreibung: With the development of economy, land reclamation by dredger fill has become an effective measure to alleviate the shortage of land resources. However, the accompanying subsidence has always been a challenge to the safe use of soil in dredger fill area. In this study, Chongming East Shoal, China, where dredger filling activities are going on in recent years was selected as the study area. SBAS-InSAR was applied to monitor the variation of land subsidence and deformation in the recent two years. Furthermore, a total of 25 undisturbed soil samples including dredger fill and underlying soil were collected from 5 boreholes (maximum depth 55 m), and the land at each borehole had different a formation time. The physical properties and compressibility were tested by laboratory tests. Results show that for the current state, fast to slow subsidence velocity was observed in the reclamation area close to the coastline, which is controlled by building load and geological features of soil layers. The building load is the main factor affecting the land subsidence and special attention should be paid. It is the poor drainage condition of the soil layer in the offshore area resulting in slow subsidence. Consolidation degree and final settlement of soil can be obtained from monitoring data of land subsidence. Based on the settlement-time curve obtained by SBAS-InSAR, the estimated final settlement of typical settlement area is −27.03 to −38.96 mm, and the corresponding consolidation degree is 58.95 % on average. It still takes a long time to achieve stability. In conclusion, land subsidence is essentially the macro-accumulation of drainage consolidation of all the soil layers, so it is controlled by soil structure and engineering geological properties of both dredger fill and underlying soil layer. The research combined with field investigation, laboratory testing can provide a mechanism explanation for monitoring results. Future research will focus on longer monitoring time and a higher sampling frequency to enrich and improve the research.

Beschreibung: The purpose of this investigation is to develop a semi-analytical procedure for quantifying aquifer and aquitard properties from a single extensometer record in lieu of the time-consuming development of more complex numerical models to quantify and constrain these parameter values. Despite a limited 12-year record and the fact that water levels both decline and increase on an annual basis, estimates of both aquifer and aquitard parameters have been reasonably estimated at the Lorenzi extensometer site in Las Vegas Valley, Nevada when compared to the estimates developed numerically. The key factors that allow for accurate estimates of elastic and inelastic skeletal specific storage and hydraulic conductivity of the aquitards and elastic specific storage and hydraulic conductivity of the intervening aquifers is the presence of pumping cycles at multiple frequencies, and measured heads at all the aquifer units covered in the extensometer record and the inherent assumption that the aquitards have identical hydrologic characteristics and are homogeneous and isotropic. This latter assumption is also a usual limitation in numerical modelling of these settings because of the complex temporal head relationships occurring within the aquitards that are rarely, if ever, measured.

Beschreibung: Detecting and mapping subsidence is currently supported by interferometric synthetic aperture radar (InSAR) products. However, several factors, such as band-dependent processing, noise presence, and strong subsidence limit the use of InSAR for assessing differential subsidence, which can lead to ground instability and damage to infrastructure. In this work, we propose an approach for measuring and mapping differential subsidence using InSAR products. We consider synthetic aperture radar (SAR) data availability, data coverage over time and space, and the region's subsidence rates to evaluate the need of post-processing, and only then we interpret the results. We illustrate our approach with two case-examples in Central Mexico, where we process SAR data from the Japanese ALOS (L-band), the German TerraSAR-X (X-band), the Italian COSMO-SkyMed (X-band) and the European Sentinel-1 (C-band) satellites. We find good agreement between our results on differential subsidence and field data of existing faulting and find potential to map yet-to-develop faults.

Beschreibung: Large-scale land subsidence often occurs after large-scale land formation caused by dredger fill, which affects the sustainable development of the region. In order to prevent and control land subsidence in the area with dredger fill, the characteristics of land subsidence and its main influencing factors need to be studied. A typical region was examined using geological survey data, land-level monitoring and comparative analysis, to provide insight regarding the variability of dredger-fill characteristics and impacts on land subsidence. The geological survey results provided the information about burial distribution characteristics of dredger fill and its underlying soil layers. The land-level monitoring results were analyzed to characterize the spatial–temporal distribution of land subsidence. The comparative analysis of land subsidence with the formation time, soil properties, thicknesses of dredger fill and the lower soft soil layer provided information about the different impacts. The monitoring results show that the land subsidence of dredger fill areas was substantially larger than that of adjacent areas. The later the filling was formed, the thicker the filling is, and the more clay-rich the soil property and the thicker the soft soil layer is, the larger the land subsidence is. Finally, the future trend of land subsidence in the study area are given and some suggestions on the prevention and control of land subsidence are also given.

Beschreibung: In Chiba prefecture in Japan, it has been reported land subsidence for many decades. One of the causes of land subsidence is considered gas production. To reduce and control land subsidence, we applied PDCA method in a certain new development area. As a result, we could maintain successfully the land subsidence less than the target value, 20 mm yr−1 at the present moment.

Beschreibung: The natural wetlands of coastal Louisiana are experiencing rapid subsidence rates averaging 9±1 mm yr−1. Recent measurements based on GPS data and CRMS surface elevation tables (SETs) have shown that most of the subsidence is shallow and occurs in the uppermost 5 meters. Sources of subsidence and the origin of their spatial variability are strongly debated. Here we use CRMS SETs together with historic maps of coastal Louisiana to explore two hypotheses: (i) shallow subsidence is a result of accommodation created by (long-term) deep subsidence processes and self-weight consolidation, and (ii) changes in marsh hydrology (groundwater and surface water flows) have led to a recent increase in shallow subsidence. First, we find that, although self-weight consolidation would result in generally high observed shallow subsidence rates, it does not explain the rates nor the spatial variability of the CRMS SET data. Second, based on historic maps, we find that shallow subsidence rates are significantly higher for CRMS sites where shipping canals have reduced their distance to the marsh edge. This is potentially a result from increased sediment deposition, but CRMS data also show altered groundwater levels near the marsh edge. We find some indication that prolonged periods of low water could have led to increases in effective stresses that explain some of the rapid rates of shallow subsidence observed along Louisiana's coastline.

Beschreibung: In the Aguascalientes valley, middle Mexico, the demand of groundwater from the local aquifer system was suddenly increased after the late 1970s. Since then, several related problems have been occurring or become critical such as land subsidence, ground fissuring, and low-magnitude earthquakes. The most recent data of vertical deformation from PSInSAR, groundwater levels, and earthquakes, has provided critical information regarding the relationship amongst all these processes. In particular, that related to land subsidence, earth fissuring and seismicity. Regarding this, more satellite imagery and data from GPS stations are being revised as a possibility of a more generalized vertical deformation derived with low-magnitude seismicity. A particular seismic event recorded on 6 April 2019 has revealed critical information on the close association between vertical displacements occurred in active faults and low-magnitude seismic events.

Beschreibung: Sinkhole activity in west-central Florida is a major hazard for people and property. Increasing frequency of sinkhole collapse is often related to an accelerated use of groundwater and land resources. In this work, we use radar interferometry acquired over a selected region in Hernando County in west-central Florida to observe small localized deformation possibly caused by sinkhole activity. The data used for the study consist of acquisitions from one TerraSAR-X frame covering a time span of approximately 1.7 years with spatial resolution of 0.25 by 0.60 m. We applied the Persistent Scatterer Interferometry (PSI) technique using the Stanford Method for Persistent Scatterers (StaMPS). Results reveal several areas of localized subsidence at rates ranging from −3.7 to −4.9 mm yr−1. Ground truthing and background verification of the subsiding locations confirmed the relationship of the subsidence with sinkhole presence.

Beschreibung: Sinkholes are common geohazards, frequently responsible for sudden catastrophic ground collapse. Thus, effective monitoring would allow for further understanding of the mechanism of occurrence of sinkholes and lead to the development of a potential early warning system to provide an alarm or a warning of incipient col-lapse. In the current study, fiber Bragg gratings (FBGs) were used to instrument reduced scale models, simulating a sinkhole event. The tests were conducted by embedding optic fiber sensors in the soil and inducing failure until critical conditions were reached. FBG sensors were manufactured in a single optic fiber cable. The measurements of small horizontal strains were recorded simultaneously and in various positions. Failure mechanism was found to relate to the backfill density, and compaction.

Beschreibung: At the start of gas production its effects on land subsidence are not certain. There are uncertainties in mechanisms, models and parameters. Examples are non-linear deformation of reservoir rock, fault transmissibility, behaviour of overlaying salt and aquifer activity. Looking back at historical cases in the Netherlands, a factor two or three difference between initial prediction and final outcome is quite common. As the Dutch regulator, SSM is tasked with assuring proper management by operators of the risks associated with land subsidence from natural gas production in The Netherlands. Large initial uncertainties can only be tolerated if operators can demonstrate that timely actions can still be taken when predefined subsidence limits are at risk of being exceeded now or in the future. The applied regulatory approach is illustrated by the case history of gas production induced subsidence in the Dutch Wadden Sea area. This environmentally highly sensitive UNESCO World Heritage Site is a natural gas province. Extensive legal, technical and organisational frameworks are in place to prevent damage to its natural values. Initial uncertainties in the predicted subsidence (rate) were later exacerbated by the detection of strong non-linear effects in the observed subsidence behaviour, leading to new concerns. It was realised that – depending on the underlying physical cause(s) – there will be a different impact on future subsidence. To assure proper management of the additional uncertainty by the operator, several improvements in the regulatory approach have been implemented. Possible underlying mechanisms had to be studied in depth and improved data analysis techniques were requested to narrow down uncertainties as time progresses. The approach involves intensified field monitoring, scenario's covering the full range of uncertainties and a particle filter approach to handle uncertainties in predictions and measurements. Spatial-temporal double differences, production data and the full covariance matrix are used to confront scenario predictions against measurements and to assess their relative probability. The regulator is actively involved in assuring this integrated control loop of predictions, monitoring, updating, mitigation measures and the closing of knowledge gaps. The regulator involvement is supported in the Mining law and by appropriate conditions in the production plan assent. With the approach it can be confidently assured that subsidence (rate) will remain within the allowed range.

Beschreibung: Land subsidence in areas with weak soils affects a large part of the Netherlands and causes many problems. To solve them diverse and specialized knowledge of possible measures to prevent, mitigate or reverse land subsidence is needed. This knowledge is fragmented over many agencies, companies and individuals. Here we show how data and knowledge are related and we stress the importance of implicit knowledge for knowledge transfer on land subsidence. It is demonstrated that land subsidence in the Netherlands is a “wicked problem”. This makes its solution cumbersome. However, we show that self-learning digital environments can help considerably in knowledge acquisition, storage and retrieval. We give an inventory of research questions that have still to be answered to make an digital environment really effective for a wicked problem like land subsidence.

Beschreibung: Land subsidence is a serious geo-hazard in Beijing Plain, which has threatened the safety of the operation of the metropolis. This study focuses on the land subsidence in the Chaobai River alluvial fan, where is the main groundwater supply region. The vertical and the East-West deformation from June 2015 to December 2017 was derived based on the SAR imaging geometry deduction. Then, the spatial variation characteristics of the deformation were analysed and the relations with the impact factors were carried out. Results show that the nugget effect (i.e., random to total spatial variance ratio) values of the vertical and the East-West deformation at regional scale were 13 % and 49 %, respectively. This indicates that the distribution of the vertical deformation is dominated by regional influencing factors, while both regional and local-scale impact factors are important for the distribution of the East–West deformation. In the southern part of the study area, the extraction of groundwater is the dominant factor affecting the spatial distribution of the vertical displacement, while the dominant factor of East-West deformation is not obvious. This study can enrich the understanding of land subsidence distribution and will help us better understand the causes of land subsidence.

Beschreibung: A tool is presented that allows efficient and largely automated production of predictive land subsidence maps on a national scale in the Netherlands. The tool, based on Python scripts, is named Atlantis and calculates the subsidence induced by phreatic groundwater level management in Holocene soft-soil areas through peat oxidation and consolidation. Process formulation, input datasets and data handling procedures are elucidated. Maps produced with Atlantis will soon be available online.

Beschreibung: A critical issue concerning geomechanical safety for UGS (underground gas storage) in compartmentalized reservoirs is fault reactivation. Indeed, the displacement (land subsidence, land upheaval) and the stress fields caused by the seasonal injection and production of CH4 into and from deep reservoirs is peculiar. The need of improving our understanding of compartmentalized reservoir behavior and to define safe bounds for the pressure fluctuation in order to prevent undesired land movements and induced seismicity is becoming even more important. This also in view of the expected energy transition when large amount of green energy will potentially be stored and recovered through UGS of compressed air or hydrogen. In this framework, an in-depth modelling investigation has been carried out for the typical UGS geological setting and operations in The Netherlands. The specific goals of the study are the following: (i) explaining the possible mechanisms responsible for seismic events unexpectedly recorded during UGS phases; (ii) understanding which are the critical factors (e.g. the geological configuration, the geomechanical properties, and the reservoir operations) that increase the probability of fault reactivation during the various UGS stages; and (iii) advancing possible guidelines for safe UGS operations. This contribution summarizes the main outcomes obtained by the modelling simulations: the combinations of factors causing fault reactivation during primary production (PP) are also more prone to generate fault failure during cushion gas injection (CG) and UGS. In fact, fault activation during PP leads to a stress redistribution and a new (deformed) “equilibrated” configuration that is newly loaded, in the opposite direction, when the pressure variation changes the sign because of CG and/or UGS. Finally, the various combinations have been ranked to highlight the conditions where the fault system is most likely reactivated during CG and UGS operations: the initial stress regime of the system, the geomechanical properties of the fault, and dislocation of the reservoir compartments are the major influencing drivers to fault instability.

Beschreibung: Mining induced subsidence in the Netherlands is often associated with small gas fields (less than 5 km diameter), or discrete sources (converging salt caverns). As most of the areas experiencing this subsidence are close to sea level, and the effects of gas exploitation in Groningen may be considered a national trauma, there is strong emphasis on control and regulation of the related mining activities and their effects at the surface. The relatively small subsidence (often less than 10 cm), combined with inherent prediction uncertainty involving geological parameters, introduces a monitoring challenge to both mining companies and the regulator. A large initial uncertainty can be reduced during production by a carefully designed monitoring strategy, including evaluation of the results and clear communication on the effects on the uncertainty of the prognosis. In the same process, one may quantify remaining uncertainties and the limitations on predictability. In this contribution, we discuss the nature of some specific uncertainties associated with small source subsidence, and the effects on the regulatory process. The description is based on a realistic assessment of the expected accuracy of subsidence predictions. This allows for a clean comparison between different measurement techniques, and may help prevent overly optimistic claims on predictability. A description of uncertainty in terms of scenarios and parameter sensitivity studies should be used in communicating the expected level of subsidence control to water management boards and the general public.

Beschreibung: This study examines how cone penetration test (CPT) parameters, such as cone tip resistance and friction sleeve resistance, can be used to assess the compressibility of fine-grained soils across the Netherlands based on a database of 286 paired CPTs and oedometer tests from across the country. This is done with the aim of refining and simplifying the parameterisation of the Koppejan consolidation coefficients, a procedure which can yield significant error and is prone to misinterpretation. It was found that there is significant potential in using gradient boosting methods to obtain a relationship between the CPT parameters and the Koppejan parameters, with further investigation required into the noise within the dataset and the acquisition of additional high-quality samples. The use of such methods will offer a means of reducing the influence of human error or misinterpretation on the prediction of settlement and provide further confidence in the use of machine learning methods in engineering practice.

Beschreibung: Underground Gas Storage (UGS) has become one of the most widely used practices to cope with seasonal peaks in energy consumption. The planning of any new UGS facility, or its upgrading to increase the working gas volume and reservoir performance, must be supported by an evaluation of possible induced effects on the environment. From a geomechanical point of view, storage activity results in a cyclic change in stress and deformation in the reservoir rock and the surrounding formations. The main environmental issues to be accounted for when natural fluid pore pressure is planned to be exceeded are the following: (a) the differential displacements at the land surface possibly mining the integrity of ground structure; (b) the integrity of the reservoir and caprock; (c) the possible reactivation of faults, if the target reservoir is located in a faulted basin; and (d) the vertical upheaval and land subsidence that can impact on the surface drainage network in low lying coastal areas. We present an original methodology for evaluating the geomechanical safety of UGS activities using an approach derived from what is traditionally applied in the structural design of buildings. A safety factor, a margin of security against risks, is defined for each of the geomechanical issues listed above. First, a 3D FE-IE numerical model is developed to reproduce the stress and displacement due to the UGS program under evaluation. Then the reservoir pressure is increased until the “failure” condition is reached allowing to evaluate how far the project designed condition is from the above limit. The proposed approach is applied to Romagna, a depleted gas reservoir in Northern Italy converted to UGS, with the aim of investigating the safety of the project to increase the reservoir pressure up to 120 % pi, where pi is the original reservoir pressure before the start of primary production. The 3D geomechanical model has been developed using recent 3D seismic data, land displacements by InSAR, lab tests on reservoir and caprock samples, in-situ Modular Formation Dynamic Tester (MDT) stress tests, and large background information acquired from other UGS reservoirs located in the same sedimentary basin. The analysis outcome has revealed that the investigated scenario is safe, with safety factor larger than 1, in the range from 1.2 to 4. The most critical condition (the smallest safety factor) has been obtained in relation to the mechanical integrity of the reservoir formation, under very conservative conditions (cohesion = 0, friction angle = 30∘).

Beschreibung: The combination of groundwater withdrawal, hydrocarbon extraction, salt-dome movement and faulting have caused widespread subsidence in the Houston-Galveston region (HGR). Subsidence results from primary consolidation consisting of inelastic (nonrecoverable) and elastic (recoverable) compaction caused by subsurface fluid withdrawal and secondary consolidation (creep) over time caused by overburden pressure. Subsidence in the HGR is monitored using borehole extensometers that were installed at 13 locations across Harris and Galveston counties between 1962 and 1980. By 1977, withdrawals from the Chicot and Evangeline aquifers resulted in groundwater-level declines of about 114 and 115 m relative to predevelopment water levels, respectively in parts of Harris County. By 1979, as much as 3 m of land subsidence was estimated to have occurred in localized areas of the HGR. Land subsidence can be hazardous in populated areas because it exacerbates the effects of storm surge and impedes storm-water runoff by decreasing land-surface elevations in areas where water accumulates. To assess aquifer compaction in response to changes in groundwater levels, a bulk land-surface subsidence rate is assumed to be the sum of the primary consolidation rate and the negligibly variable component of overburden pressure referred to as the “pseudo-constant secondary consolidation rate.” From 1931 to 1976, groundwater levels decreased as groundwater withdrawal rates increased from 0.57 to 4.3 million m3 d−1, causing pressure heads in aquitards the Chicot and Evangeline aquifers to continually decline. In response to reductions in groundwater withdrawal rates from 4.3 to 3.0 million m3 d−1 between 1976 and 2001, groundwater levels rebounded, decreasing inelastic compaction rates in some parts of the HGR from as much as about 40 mm yr−1 in the early 1980s to negligible amounts by 2000. Inelastic consolidation from about 1937 to 2000 contributed to land-surface subsidence and its associated effects. Land-surfaces have rebounded in localized areas of the HGR where groundwater levels rebounded significantly. Pseudo-constant secondary consolidation rates were computed at each of the 13 extensometers and ranged from 0.48 to 8.49 mm yr−1 in areas where groundwater levels in the two aquifers were stabilizing. This secondary consolidation subsidence is beyond the control of any groundwater-level management schemes because it is caused by geohistorical overburden pressure on the two aquifers.