Study on High-Resolution Suspended Sediment Distribution under the Influence of Coastal Zone Engineering in the Yangtze River Mouth, China

Lina Cai,Juan Bu,Xiaojun Yan,Songyu Chen,Yan Bai

doi:10.3390/rs14030486

Abstract

In this study, we analyzed the influence of coastal zone engineering on suspended sediment concentration (SSC) in the Yangtze River mouth based on HY-1C and Chinese GaoFen (GF) satellite data. The results show that: (1) SSC in the Yangtze River mouth is mainly in the range of 200–1300 mg/L, which changes due to natural factors as well as coastal zone engineering; (2) The sand blocking engineering effectively protects the channel from siltation, and SSC in the central line of the channel is 100–300 mg/L lower than that near the dikes in the north and south; (3) Qingcaosha Reservoir plays a stabilizing role in the hydrodynamic force, promoting the deposition of suspended matter, so that the water in the reservoir is clear. SSC inside the Qingcaosha Reservoir, located in the center of the estuary, is 100–500 mg/L lower than the high SSC water outside the reservoir; (4) The bridges interact with the current, facilitating the transport of local sediment, resulting in the increase in SSC downstream of these bridges, and obvious vortexes appear with the length up to nearly 2400 m; and (5) Corresponding protection and development suggestions were put forward as follows. A linear array of wind power plants can be built near and parallel to dikes and leading jetties; to increase the depth of the southeast end of the reservoir; and the location of the bridge should be selected in the place of river where siltation is easy. This study aimed to study the SSC distribution under the complex impact of coastal zone engineering with satellite and to provide possible improvement suggestions.

Highlights

As the longest river in Asia, the Yangtze River is approximately 6300 km long and its annual runoff and sediment volume rank the fifth and fourth in the world, respectively [1].The Yangtze River carries 3.84 × 108 tons of sediment to the sea every year [2], bringing a huge amount of suspended sediment (SS) to the Yangtze River mouth.SS plays a crucial role in the ecology and topography development of the estuary
At the beginning of the flooding period, the current flows from the west of Hangzhou Bay to the east of the bay (Figure 3a), whereas at the beginning of ebbing period (Figure 3f), the currents flow in the opposite direction compared with the flooding period
The suspended sediment concentration (SSC) in the Yangtze River mouth is high, ranging from 200 to 1300 mg/L, and the high-value area is concentrated in the isobathic line of 10 m, which gradually increases from west to east

Summary

Introduction

As the longest river in Asia, the Yangtze River is approximately 6300 km long and its annual runoff and sediment volume rank the fifth and fourth in the world, respectively [1].The Yangtze River carries 3.84 × 108 tons of sediment to the sea every year (from 1950 to2011) [2], bringing a huge amount of suspended sediment (SS) to the Yangtze River mouth.SS plays a crucial role in the ecology and topography development of the estuary. Sediment transport is closely related to many kinds of estuarine engineering [5,6,7,8], including the construction of artificial islands, tunnel construction, and dredging projects—projects which complicate the dynamics of sediment in estuaries [9]. Considering all these factors, it is of paramount significance to study the distribution and transport of SS in the Yangtze River mouth for environmental protection, construction evaluation, and later engineering instruction

Objectives

Results

Discussion

Conclusion