Sinking coastal cities

Abstract

Abstract. In many coastal and delta cities land subsidence now exceeds absolute sea level rise up to a factor of ten. A major cause for severe land subsidence is excessive groundwater extraction related to rapid urbanization and population growth. Without action, parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other coastal cities will sink below sea level. Land subsidence increases flood vulnerability (frequency, inundation depth and duration of floods), with floods causing major economic damage and loss of lives. In addition, differential land movement causes significant economic losses in the form of structural damage and high maintenance costs for (infra)structure. The total damage worldwide is estimated at billions of dollars annually.As subsidence is often spatially variable and can be caused by multiple processes, an assessment of subsidence in delta cities needs to answer questions such as: what are the main causes? What is the current subsidence rate and what are future scenarios (and interaction with other major environmental issues)? Where are the vulnerable areas? What are the impacts and risks? How can adverse impacts be mitigated or compensated for? Who is involved and responsible to act?In this study a quick-assessment of subsidence is performed on the following mega-cities: Jakarta, Ho Chi Minh City, Dhaka, New Orleans and Bangkok. Results of these case studies will be presented and compared, and a (generic) approach how to deal with subsidence in current and future subsidence-prone areas is provided.

Coastal sea level rise with warming above 2 °C

“…Guangzhou may be globally the most economically vulnerable city to rising sea levels by the middle of the 21st century, with estimated losses of $254 million per year under a sea level rise of 0.2 m (4); however, other cities in India, Bangladesh, and Southeast Asia (Table 2 and Table S2) will likely have larger populations at risk by that date (29,30). In several coastal cities, current land subsidence exceeds observed sea level rise (15,28,31,32). Economic development in urban areas of megacities drives the growing demand for groundwater, therefore increasing subsidence rates, with 2025 projected (15,28) 2 m), and the western Netherlands (0.07 m).…”

“…In several coastal cities, current land subsidence exceeds observed sea level rise (15,28,31,32). Economic development in urban areas of megacities drives the growing demand for groundwater, therefore increasing subsidence rates, with 2025 projected (15,28) 2 m), and the western Netherlands (0.07 m). The costs of local rising sea levels for coastal cities will be much larger than those due to socioeconomic changes, and could amount to US $ 1 trillion per year in the absence of appropriate adaptation measures (4).…”

“…The costs of local rising sea levels for coastal cities will be much larger than those due to socioeconomic changes, and could amount to US $ 1 trillion per year in the absence of appropriate adaptation measures (4). Subsidence projected for Jakarta by 2100 varies between 2.3 m and 3.0 m, depending on groundwater management scenario (28). Hence, individual city actions allow for mitigation of, or must provide adaptation to, subsidence; this contrasts with climatedriven sea level rise, which is a global problem that requires global solutions.…”

Retos y oportunidades para el aprovechamiento y manejo ambiental del ex lago de Texcoco

“…Este tipo de sistema inyecta agua debidamente tratada al subsuelo según la NOM-014-CONAGUA-2003 y la NOM-015-CONAGUA-2007 a través de pozos perforados ex profeso (Mendoza-Archundia, 2012). Otras megaciudades, como la de Tokio, han logrado detener su hundimiento evitando la extracción de aguas subterráneas, mostrando que el problema de la subsidencia tiene solución mediante la recuperación de los acuíferos, la planeación territorial y el uso de materiales de construcción más ligeros (Erkens et al, 2014a(Erkens et al, , 2014b.…”

Predicting Dynamic Coastal Delta Change in Response to Sea-Level Rise

“…For example, the Amazon delta in Brazil is located in a region with a higher-than-global-mean SLR and coastal impacts are therefore expected to be more severe, while the Ganges delta in India and Bangladesh is located in a region with a lower-than-global-mean SLR and coastal impacts of climate-change driven SLR are therefore expected to be less severe. It is, however, important to note that the aforementioned coastal impacts are only related to SLR and not to land subsidence [32,33], which is substantial in the Ganges delta region and will be discussed in more detail in Section 4. Despite being shaped by different degrees of fluvial input and marine reworking, our results indicate a similar ability to dynamically respond to SLR for the aforementioned deltas thus rendering them unable to mitigate the regional differences in SLR.…”