A study of the surficial suspended sediment concentration in response to typhoons in the Yangtze Estuary
2019, 2019 (2):
Suspended sediment concentration (SSC) is an important index to measure water quality, and its variations have major influences on seabed erosion/accretion, biological primary productivity, and restoration/loss of land resources. To study the influence of typhoons on the SSC in the Yangtze Estuary, we used surficial SSC data collected at six gauging stations-namely Xuliujing, Qinglonggang, Gaoqiao, Hengsha, Sheshan, and Luchaogang-over the period from 2010 to 2014, as well as continuous data on wind speeds and wave heights over long time scales. The results indicated that wave heights and wind speeds during typhoons were on average 2.2 times and 1.7 times higher, respectively, than those before a typhoon occurred. The mean surficial SSC at the gauging stations also doubled, increasing from 0.32 kg/m3 before typhoons to 0.69 kg/m3 during typhoons. The SSC measured during typhoons was found to be 4 times larger than values observed during calm weather. The typhoons' influences on SSC, moreover, varied across different sections of the Yangtze Estuary. Influences measured at the Sheshan and Luchaogang stations in the outer estuary were the most significant, and the SSC at the two stations increased by 167.1% and 143.7%, respectively. However, the sensitivity of SSC to the typhoons was relatively minor in the inner estuary, where winds' influences were accordingly minimal. Based on long time scale data, the increase of SSC was moderate for wind scales 1-4, and the increase of SSC became evident above a wind scale of 5. Changes in wind speeds and wave heights, resulting from typhoons, were the most dominant factors attributing to the varation in surficial SSC. During typhoon season, the change of surficial SSC caused by typhoons is much greater than the change of surficial SSC due to tidal and runoff effects. This study is beneficial to the protection of coastal engineering during typhoons and has important implications for the study of interdisciplinary fields.
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