Abstract:

This study examines spatial and temporal changes in the continental coastline and the intertidal zone from the Xiuzhen estuary to the Lianxing estuary in Jiangsu province from 1984 to 2016. This work employed an improved water-line method based on 61 multi-source remote-sensing images, as well as tide and measured slope data. The coastline is a combination of the mean high-tide line and artificial coastline. The mean high-tide line was derived from elevation data contained in the waterlines through the improved water-line method. Water lines were extracted from remote sensing images using object-oriented classification, band operation, etc. Then, tides at the tide stations at image acquisition times were predicted using the T-Tide program. The predicted tides were assigned to water lines and intertidal slopes were calculated. Finally, mean high-tide and low-tide lines were determined from measured and calculated slopes. The quantitative analysis of the coastline, mean low tide line, and intertidal zone yielded the following main conclusions. From 1984 to 2016, Jiangsu's coastline advanced mainly towards the sea because of coastal development. The natural shoreline decreased from 458.24 to 166.74 km, while the artificial shoreline increased from 163.66 to 598.74 km. The length of Jiangsu’s continental coastline also increased from 621.90 to 765.48 km. During this period, the positions and lengths of different segments of the coastline changed. The deposited coast, which advanced toward the sea at an annual rate of 83.03 m, was 127.62 km long. The reclaimed coast, which advanced towards the sea at an annual rate of 87.63 m, was 401.21 km. The erosional coast, which receded at an annual rate of 10. 81 m, was 71.17 km long. The eroded reclaimed coast, which receded at an annual rate of 8.64 m, was 25.95 km long. The area of Jiangsu underwent a net increase of 104332 hm², primarily due to reclamation, with reclaimed land representing 98520 hm². Erosion mainly occurred in the abandoned Yellow River Delta, but during 2008-2016, it extended southward from the Xinyang to the Doulong harbor. The slopes of the intertidal zone became steeper due to reclamation and shoreline erosion, changing from 1.4‰ to 1.9‰. The abandoned Yellow River Delta experienced the most severe change in slope, with its mean slope in the range of 3‰-14‰. The mean slope of the radial sandbank of the onshore coast, which had the gentlest slope, increased from 0.9‰ to 1.5‰. The intertidal area decreased by 38% from 271747 to 168645 km², while the mean width of the intertidal zone decreased by 39% from 5064 m to 3096 m.

Key words: Jiangsu province, coastline, intertidal zone, spatial and temporal change, remote sensing