Multiple sensors applied to monitorland subsidence in Central Taiwan

Hung, Wei Chia; Wang, C.; Hwang, Cheinway; Chen, Y. A.; Chiu, Hsiang Chih; Lin, Shih-Yuan

doi:10.5194/piahs-372-385-2015

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…thus, suitable for distinguishing between various factors that determine subsidence over a compacting aquifer and that act at different depth intervals 145 . To measure the compaction of layers at different depths within a single borehole, an extensometer can include an array of spider magnets anchored at each depth, the readings of which refer to the top or bottom of the borehole 146 .…”

Section: Sea Surface Geoidmentioning

confidence: 99%

Measuring, modelling and projecting coastal land subsidence

Shirzaei

Freymueller

Törnqvist

et al. 2020

Nat Rev Earth Environ

159

120

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A large proportion of the world's population lives on low-elevation (<10 m) land near the sea 1,2 , much of which is subject to subsidence due to natural and anthropogenic processes 3 . As of 2005, ~40 million people and assets worth 5% of global gross domestic product were exposed to a 1-in-100-year coastal flooding hazard 4 . By 2070, the exposed population is expected to grow more than threefold, and the value of property exposed is expected to increase to ~9% of the projected gross domestic product, with the USA, Japan and the Netherlands having the most exposure 4 . However, these estimates often rely only on projections of global average sea-level rise and do not account for vertical land motion (VLM), in terms of subsidence (downward VLM) or uplift (upward VLM) of the land surface. A different estimate of exposure could result when VLM is taken into account, particularly considering recent findings that the elevation of many coastal lowlands has, to date, been considerably overestimated 5 .The recent increase in global mean sea level (GMSL) has led to a present-day rate of rise of ~3.35 mm per year (ref. 6 ); GMSL rise since 1900 is mostly attributed to accelerated ice-mass loss of glaciers and ice sheets, plus the thermal expansion of ocean water 7 . However, the relative sea level (RSL), defined here as the elevation difference between the sea surface and the solid Earth 8 , excluding the dynamic sediment surface 9 , is of particular relevance for assessing the effects of sea-level change at any given location. RSL change is defined as the sum of geocentric sea-level change plus VLM 8 . Note that the sediment-accretion rate, which has sometimes been invoked as a term in the RSL equation 10 , merely affects local water depth, not RSL. VLM is driven by natural processes, such as glacial isostatic adjustment (GIA) [11][12][13] , tectonics and earthquakes 14,15 , and sediment consolidation, including natural compaction owing to sediment deposition (loading) [16][17][18][19] , as well as anthropogenic effects caused by peat oxidation following drainage [20][21][22][23][24] and the compaction of aquifer systems and hydrocarbon reservoirs accompanying the extraction of subsurface fluids 20,25,26 (fig. 1).These drivers can be divided into shallow processes affecting depths of less than ~25 m (for example, compaction of Holocene sediments) and deep processes (such as tectonics and compaction of pre-Holocene strata) 27 . VLM can be much greater than nearby geocentric sea-level rise alone and, in turn, GMSL rise, which is estimated, in part, based on tide-gauge records. Thus, knowing how much, where and why coastal land subsides and how its rate varies over time is essential to evaluating hazards associated with sea-level rise and estimating GMSL rise.

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Section: Sea Surface Geoidmentioning

confidence: 99%

Measuring, modelling and projecting coastal land subsidence

Shirzaei

Freymueller

Törnqvist

et al. 2020

Nat Rev Earth Environ

159

120

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“…On the contrary, if the major compaction occurs at a shallow stratum, agricultural water is the main source of water use. (Hung et al., 2015: 388)In 2002, the WRA published a report which revealed that land subsidence of 4 centimetres per year was observed along the planned, high-speed routes in Yunlin County. Politicians immediately held a press conference in which they maintained that the land subsidence would pose potential risk to the high-speed rail infrastructure.…”

Section: Securing the Subterranean Volumes: Modern Geological Knowledmentioning

confidence: 99%

“…On the contrary, if the major compaction occurs at a shallow stratum, agricultural water is the main source of water use. (Hung et al., 2015: 388)…”

Section: Securing the Subterranean Volumes: Modern Geological Knowledmentioning

confidence: 99%

“…The focus on the unruly inter-material relations resonates with assemblage thinking which contends that the properties of a whole have emergent properties that develop from the interactions between its parts. From this perspective, although the engineers firmly claim that the compaction monitoring well can effectively make sense of the subterranean volumes (Hung et al., 2015), the heterogeneity in soil compositions and inter-material relations routinely pose challenges for geoscientists. The disagreement between engineers and scientists also indicates that political technologies of the subterranean spaces fail to control the relations between disparate materials.…”

Section: (Re)assembling the Subterranean Volumes: A Representation Ofmentioning

confidence: 99%

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Securing the subterranean volumes: Geometrics, land subsidence and the materialities of things

Wang

2020

Environ Plan D

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In 2011, thousands of Taiwanese farmers gathered in Yunlin County to protest against a government environmental management programme which attempted to address the land subsidence that has threatened Taiwan’s High-Speed Rail infrastructure. New environmental monitoring technologies have been developed to deal with the land subsidence but these have, simultaneously, provoked contestation. The dispute indicates that the horizontalism inherent in traditional studies of geopolitics fails to account for the politics of verticality. Indeed, recent work on volumetric politics opens up new horizons for thinking about the exercise of power through three dimensions; the geopolitics of the underground have remained untheorised. Moreover, the existing literature on volume also fails to account for the chaotic state of the material world. From the perspective of assemblage thinking, I outline three characteristics which shape the ‘geopolitics of land subsidence’. From this standpoint, this paper argues for a geographical approach to subterranean politics which puts more emphasis on volume, emergence and matter. With reference to ethnographical fieldwork conducted in scientific laboratories and in Yunlin County, I demonstrate how subterranean materials continuously frustrate the state’s volumetric practices. By problematising the geopolitics of land subsidence, this paper also advances the understanding of political geology, which is seeking to ‘decolonise’ and ‘pluralise geological thought’.

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