Mapping Trajectories of Coastal Land Reclamation in Nine Deltaic Megacities using Google Earth Engine

Abstract

Increasing demand for land resources at the coast has exerted immense pressure on vulnerable environments. Population and economic growth in coastal cities have combined to produce a scarcity of suitable space for development, the response to which has frequently been the reclamation of land from the sea, most prominently in China. Urbanization is a key driver of such changes and a detailed investigation of coastal land reclamation at the city scale is required. This study analyzed remote sensing imagery for the period 1990 to 2018 to explore the trajectories of coastal land reclamation in nine major urban agglomerations across the three largest deltas in China using the JRC Global Surface Water (Yearly Water Classification History, v1.1) (GSW) dataset on the Google Earth Engine platform. The results are considered in the context of major national policy reforms over the last three decades. The analysis reveals that total land reclaimed among nine selected cities had exceeded 2800 km2 since 1984, 82% of which occurred after 2000, a year following the enactment of China’s agricultural ‘red line’ policy. Shanghai exhibited the greatest overall area of land extension, followed by Ningbo and Tianjin, especially in the period following the privatization of property rights in 2004. In analyzing annual trends, we identified the developmental stages of a typical coastal reclamation project and how these vary between cities. Scrutiny of the results revealed voids in nighttime light satellite data (2014–2018) in some localities. Although these voids appeared to be characterized by construction, they were occupied by vacant buildings, and were therefore examples of so-called “ghost cities.” In China, as elsewhere, continual land reclamation needs to be considered in relation to, inter alia, sea level rise and land subsidence that pose significant challenges to the vision of sustainable urban development in these three deltaic megacities.

The Case for a Critical Zone Science Approach to Research on Estuarine and Coastal Wetlands in the Anthropocene

“…The markedly reduced fluvial sediment loads have, as expected, resulted in recession of the Yangtze delta (Luo et al (2017), although impacts on the wider estuarine environment have not always been as anticipated (Zhu et al 2019). Indeed, accretion of mudflats has actually increased in many localities around the Yangtze estuary due to lower annual discharge and reduced flood frequencies (Hu et al 2019), a situation that has been further promoted through land reclamation (Sengupta et al 2019).…”

Remote Sensing Applications in Monitoring of Protected Areas

“…The improved capacity of data science and infrastructure, e.g., cloud computing, Google Earth Engine (GEE) and big Earth data approaches, facilitates data sharing and the integration and modeling processes [87][88][89]. For example, the capacity and service from GEE open opportunities for explorations that benefit from decades of data acquisition from remote sensing [90][91][92][93][94][95][96].…”

Hydrogeology of Reclaimed Floodplain in A Permafrost Area, Yakutsk, Russia

“…Construction activities on this site started in 2013. The total area of the reclaimed land is 0.67 km 2 , and the thickness of the fill mass ranges from 4 to 15 m. The surface of the fill ground has elevations of 97-98 m to protect against flooding. strategic planning of future development in floodplain environments.…”

“…The most common method of land reclamation in seasonally flooded areas is hydraulic filling. Major hydraulic fill projects have been undertaken in the Netherlands, Denmark, Dubai, China, Singapore, and Japan [1,2]. In Russia, several neighborhoods in St. Petersburg were built on the land reclaimed by hydraulic filling; smaller-scale projects were also undertaken in Omsk, Nizhny Novgorod, Arkhangelsk, Perm, and Kazan [3][4][5][6][7][8].…”