Abstract
Estuaries have been sites of intensive human activities during the past century. Tracing the evolution of subaqueous topography in estuaries on a decadal timescale enables us to understand the effects of human activities on estuaries. Bathymetric data from 1955 to 2010 show that land reclamation decreased the subaqueous area of Lingding Bay, in the Pearl River estuary, by ~170 km2 and decreased its water volume by 615 × 106 m3, representing a net decrease of 11.2 × 106 m3 per year and indicating the deposition of approximately 14.5 Mt/yr of sediment in Lingding Bay during that period. Whereas Lingding Bay was mainly governed by natural processes with slight net deposition before 1980, subsequent dredging and large port engineering projects changed the subaqueous topography of the bay by shallowing its shoals and deepening its troughs. Between 2012 and 2013, continuous dredging and a surge of sand excavation resulted in local changes in water depth of ± 5 m/yr, far exceeding the magnitude of natural topographic evolution in Lingding Bay. Reclamation, dredging, and navigation-channel projects removed 8.4 Mt/yr of sediment from Lingding Bay, representing 29% of the sediment input to the bay, and these activities have increased recently.
Highlights
Estuaries have been sites of intensive human activities during the past century
The subaqueous topography of Lingding Bay was strongly affected by human activities from 1955 to 2010
As a result of land reclamation, the area covered by water in the Lingding Bay study area decreased from 1010 km[2] to 833 km[2], and the area of tidal flat decreased from 215 km[2] to 159 km[2] over this period
Summary
Estuaries have been sites of intensive human activities during the past century. Tracing the evolution of subaqueous topography in estuaries on a decadal timescale enables us to understand the effects of human activities on estuaries. The five great rivers of East and Southeast Asia—the Yellow (Huanghe), Yangtze (Changjiang), Pearl (Zhujiang), Red (Song Hong), and Mekong—are key regions for studies of the impact of human activities on deltas. As these five rivers have been increasingly affected by damming, the amount of terrigenous material transported from this region to the western Pacific has dropped from ~2,000 Mt/yr to ~600 Mt/yr over the last millennium[6]. More than 14,000 reservoirs have been built in the Pearl River drainage basin, trapping large amounts of sediment and causing a drastic decrease in sediment transport[20,21,22,23,24]
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