Effects of Human Activities on Submarine Topography in Lingding Bay of the Pearl River Estuary During the Last Decade

Abstract:

Estuaries have been the site of intensive human activities. During the past century, decreased fluvial water and sediment discharge, increasing land reclamation, changing climate, and rising sea level have had an ever-increasing impact on river deltas, particularly those deltas bordering Southeast Asia. Using six stages of navigational and bathymetric chart data from 1906 to 2013 and 2 years (2012,2013) single-beam bathymetric data, together with more than 50 years of fluvial discharge data, we document the impact of human activities on the Pearl River Delta and its estuary at Lingding Bay. Between 1906 and 2010, land reclamation decreased the bay’s water area by ~300 km² (>17%), mostly at the expense of the shrinking intertidal and shallow subtidal mudflats. Before 1980, the estuary was mainly governed by natural processes with slight net deposition, whereas after 1980 dredging in the estuary and large port engineering projects changed the estuarine topography by shallowing the shoals and deepening the troughs. From 1955 to 2010, the water volume of Lingding Bay decreased by 536 × 10⁶ m³ for a net decrease of 9.7 × 10⁶ m³ a year, which indicates that approximately 9.7 Mt/yr of sediment was deposited in Lingding Bay during that period. In 2012 and 2013, large-scale human activities within Lingding Bay included continued dredging plus a surge of sand excavation that changed local water depths by ±5 m/yr, far exceeding the range of natural topographic evolution in the estuary. The impacts of various human activities have significantly changed submarine topography in Lingding Bay of the complex Pearl River Estuary. With continuing economic expansion in the Pearl River Delta, Lingding Bay should continue to shrink in both area and water volume.