Abstract
Hangzhou Bay (HZB) is the largest macro-tidal bay in China, where suspended sediment concentrations are significantly modulated by tidal oscillations. This makes it an ideal area for the study of the impact of tide on temporal–spatial variation in suspended sediment. The GaoFen-4 (GF-4) satellite is the first high-resolution geosynchronous orbiting satellite of China. It exhibits the unique advantages of capturing minute variations and finer details of total suspended matter (TSM) due to the enhancement in spatial resolution (50 m) and observation time interval (20 s). In this study, TSM concentration of the HZB was retrieved based on the GF-4 satellite. The spatial distribution and minute variations of TSM concentration under the ebb tide from 7:30 to 7:40 a.m. on 28 August 2017, were analyzed. The results showed that the average TSM concentration inside HZB was (371.8 ± 1.8) mg/L. There was a linearly increasing trend of TSM concentration at ebb tide, with an increment of (3.96 ± 0.31) (mg/L)/min, and a more significant increase was observed in the high TSM areas. This increase in TSM concentration was associated with both the bottom topography and tide processes. The tidal potential energy generated by the tidal range and the strong shear stress generated by the high current velocity both led to the re-suspension of the sedimentary particles, which affected the variation of TSM concentration. In addition, the influence of bottom topography changed the intensity of re-suspension and also affected the distribution of TSM concentration in HZB.
Highlights
The average Total suspended matter (TSM) concentration inside Hangzhou Bay (HZB) ((371.8 ± 1.8) mg/L) was significantly higher than that at the mouth of HZB ((109.6 ± 3.0) mg/L), and there were four high TSM concentration zones and two low TSM concentration zones inside HZB at ebb tide, which was basically consistent with the results of previous studies [24,25]
The tidal potential energy generated by the tidal range and the strong shear stress generated by the high current velocity both lead the sediment to be disturbed and resuspended in the water, which may be the main reason for the increase of TSM concentration in HZB [5,23]
Based on the study of remote sensing of TSM concentration in HZB using GF-4 satellite data and the analysis of TSM concentration variation, the following conclusions were drawn in this paper: (1) The average TSM concentration in HZB was (371.8 ± 1.8) mg/L during the study period
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Suspended sediments can affect the water quality, ecosystem, and bottom geomorphologic evolution in estuaries and bays [1,2]. They are an important indicator of the sediment transport and resuspension process [3,4]. The exchanges of particles such as sediment can be influenced by the tide in estuaries and bays [5].
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