Abstract
Human activities such as the rapid development of marine aquaculture in the central Jiangsu coast have had a marked impact on the tidal flat morphology. This research focuses on characterizing the spatial expansion of laver cultivation and its influence on the sedimentary evolution of tidal flats in the central Jiangsu coast. First, seasonal digital elevation models (DEMs) were established using 160 satellite images with medium resolution. Then, laver aquaculture regions were extracted from 50 time-series satellite images to calculate the area and analyze the spatial distribution and expansion of these areas. Finally, seasonal and intra-annual sedimentary evolution patterns of both aquaculture and non-aquaculture regions were determined using the constructed DEMs. Our results show that aquaculture regions have gradually expanded to the north and peripheral domains of the entire sand ridge since 1999 and by 2013, the seaward margins of each sandbank developed into dense cultivation regions. Additionally, the aquaculture regions increased from 11.99 km2 to 295.28 km2. The seasonal sedimentary evolution patterns indicate that deposition occurs during the winter and erosion during the summer. Thus, the aquaculture regions experience deposition in certain elevation intervals during the laver growing period and in the non-growing period, alluvial elevation intervals in the aquaculture regions are eroded and erosive ones are deposited in order to maintain the balance between scouring and silting. The sedimentary evolution of each sandbank is heterogeneous due to their different locations and the difference in sediment transport. The intra-annual evolution pattern is characterized by deposition in the high tidal flats and erosion in low ones. Hydrodynamic conditions and laver cultivation dominate partial sedimentary evolution, which gradually shapes the beach surface.
Highlights
Tidal flats are broad areas between the mean high tide and mean low tide levels [1], which are the most promising areas for ocean exploitation [2]
The purpose of this study is to investigate the sedimentary evolution of tidal flats in response to laver cultivation using a time series strategy that employs satellite remote sensing images
From the perspective of spatial expansion, laver aquaculture regions were distributed only in the Jiangjiasha sandbank and the southern coast in 1999, which covered only 11.99 km2 initially calculated from satellite images
Summary
Tidal flats are broad areas between the mean high tide and mean low tide levels [1], which are the most promising areas for ocean exploitation [2]. They provide developmental space for fisheries, agricultural land and harbor construction, as well as serve ecological and environmental functions [3,4]. Due to natural factors and increasingly intensive human activities, tidal flats are dynamically affected and facing grim challenges [6,7]. Understanding the changes in the topography of the mudflat can provide fundamental information and scientific evidence for environmental management, tidal-flat protection, coastal development and economic exploitation [15]
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