Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary
Sedimentation is an important mechanism to mitigate the shrinking of tidal flat and to restore its ecological function by means of sand or mud nourishment. To explore the sedimentation of cohesive sediments, a seabed tripod observation system was deployed at the subtidal region of the Hengsha Shoal...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2023-01-01
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| Series: | Frontiers in Marine Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmars.2022.1045335/full |
| _version_ | 1797955321931497472 |
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| author | Qi Shen Qin Zhu Shuguang Liu Sha Lou Hualin Wu Zhenchang Zhu Bin Xu Rui Yuan |
| author_facet | Qi Shen Qin Zhu Shuguang Liu Sha Lou Hualin Wu Zhenchang Zhu Bin Xu Rui Yuan |
| author_sort | Qi Shen |
| collection | DOAJ |
| description | Sedimentation is an important mechanism to mitigate the shrinking of tidal flat and to restore its ecological function by means of sand or mud nourishment. To explore the sedimentation of cohesive sediments, a seabed tripod observation system was deployed at the subtidal region of the Hengsha Shoal adjacent to the turbidity maximum zone of the Yangtze Estuary for 11 days. The results showed that the fine sediment with the median grain size around 8 mm occupied the whole water column. The seabed was in relative equilibrium state with the fluctuation of bed level smaller than 16 mm during the moderate wind condition while the seabed experienced a rapid erosion of 38mm and a successive intensive accretion of 68mm during the process of wind wave and swell. The bottom hydrodynamic at 0.3mab during the bed accretion was stronger than that during the bed erosion. The deposition process of cohesive sediments can be better described by the simultaneous deposition paradigm than that by the exclusive deposition paradigm according to the direct data-model comparison of the bed level changes, especially during the impact of fluid mud. Three possible reasons for the better performance of the simultaneous deposition paradigm were proposed. The first possibility is that the fine suspended sediments do maintain a continuous contact with the sediment bed since the direct bed level changes during our observation period has been well reproduced by the simultaneous deposition paradigm. The second possibility is the SSC-induced turbulence damping which facilitates the fine sediment settling in the form of cohesive sediment flocs, indicating the settling of sediments can’t be judged by the critical shear stress for deposition just based on the single particle grain size. The last possibility is the fluid mud-induced overestimated bed shear stress by using turbulent velocity fluctuation above the fluid mud-water interface, which produces excess sediment erosion waiting to be compensated by the simultaneous deposition paradigm. For practical modeling purposes, modeling under the simultaneous deposition paradigm can give satisfactory results for the sedimentation of cohesive sediment especially during the impact of wave or swell. |
| first_indexed | 2024-04-10T23:31:16Z |
| format | Article |
| id | doaj.art-f6d1c9bcde8d4cadb0a540d67b1b4000 |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-04-10T23:31:16Z |
| publishDate | 2023-01-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-f6d1c9bcde8d4cadb0a540d67b1b40002023-01-12T06:42:25ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452023-01-01910.3389/fmars.2022.10453351045335Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuaryQi Shen0Qin Zhu1Shuguang Liu2Sha Lou3Hualin Wu4Zhenchang Zhu5Bin Xu6Rui Yuan7Key Laboratory of Estuarine and Coastal Project, Ministry of Transport, Shanghai Estuarine and Coastal Science Research Center, Shanghai, ChinaResearch Centre of Ecology & Environment for Coastal Areas and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, ChinaDepartment of Hydraulic Engineering, Tongji University, Shanghai, ChinaDepartment of Hydraulic Engineering, Tongji University, Shanghai, ChinaKey Laboratory of Estuarine and Coastal Project, Ministry of Transport, Shanghai Estuarine and Coastal Science Research Center, Shanghai, ChinaResearch Centre of Ecology & Environment for Coastal Areas and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, ChinaKey Laboratory of Estuarine and Coastal Project, Ministry of Transport, Shanghai Estuarine and Coastal Science Research Center, Shanghai, ChinaDepartment of Ocean Science and Engineering, Shanghai Maritime University, Shanghai, ChinaSedimentation is an important mechanism to mitigate the shrinking of tidal flat and to restore its ecological function by means of sand or mud nourishment. To explore the sedimentation of cohesive sediments, a seabed tripod observation system was deployed at the subtidal region of the Hengsha Shoal adjacent to the turbidity maximum zone of the Yangtze Estuary for 11 days. The results showed that the fine sediment with the median grain size around 8 mm occupied the whole water column. The seabed was in relative equilibrium state with the fluctuation of bed level smaller than 16 mm during the moderate wind condition while the seabed experienced a rapid erosion of 38mm and a successive intensive accretion of 68mm during the process of wind wave and swell. The bottom hydrodynamic at 0.3mab during the bed accretion was stronger than that during the bed erosion. The deposition process of cohesive sediments can be better described by the simultaneous deposition paradigm than that by the exclusive deposition paradigm according to the direct data-model comparison of the bed level changes, especially during the impact of fluid mud. Three possible reasons for the better performance of the simultaneous deposition paradigm were proposed. The first possibility is that the fine suspended sediments do maintain a continuous contact with the sediment bed since the direct bed level changes during our observation period has been well reproduced by the simultaneous deposition paradigm. The second possibility is the SSC-induced turbulence damping which facilitates the fine sediment settling in the form of cohesive sediment flocs, indicating the settling of sediments can’t be judged by the critical shear stress for deposition just based on the single particle grain size. The last possibility is the fluid mud-induced overestimated bed shear stress by using turbulent velocity fluctuation above the fluid mud-water interface, which produces excess sediment erosion waiting to be compensated by the simultaneous deposition paradigm. For practical modeling purposes, modeling under the simultaneous deposition paradigm can give satisfactory results for the sedimentation of cohesive sediment especially during the impact of wave or swell.https://www.frontiersin.org/articles/10.3389/fmars.2022.1045335/fullsedimentationcohesive sedimentswave and swellhigh turbidity estuarysubtidal flat |
| spellingShingle | Qi Shen Qin Zhu Shuguang Liu Sha Lou Hualin Wu Zhenchang Zhu Bin Xu Rui Yuan Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary Frontiers in Marine Science sedimentation cohesive sediments wave and swell high turbidity estuary subtidal flat |
| title | Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary |
| title_full | Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary |
| title_fullStr | Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary |
| title_full_unstemmed | Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary |
| title_short | Sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary |
| title_sort | sedimentation of cohesive sediments at the subtidal flat affected by wind wave in high turbidity estuary |
| topic | sedimentation cohesive sediments wave and swell high turbidity estuary subtidal flat |
| url | https://www.frontiersin.org/articles/10.3389/fmars.2022.1045335/full |
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