Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System

Erosion of cohesive sediments is a ubiquitous phenomenon in estuarine and intertidal environments. Several methods have been proposed to determine the surface erosion threshold (τc0), which are still debatable because of the numerous and uncertain definitions. Based on erosion microcosm experiments,...

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Autores principales:	Hun Jun Ha, Ho Kyung Ha
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	erosion threshold intertidal flat cohesive sediment methods microcosm system Science Q General. Including nature conservation, geographical distribution QH1-199.5
Acceso en línea:	https://doaj.org/article/007b2a21f79c4d3cb5520ec39eeb3888
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spelling	oai:doaj.org-article:007b2a21f79c4d3cb5520ec39eeb38882021-11-04T05:03:16ZComparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System2296-774510.3389/fmars.2021.695845https://doaj.org/article/007b2a21f79c4d3cb5520ec39eeb38882021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fmars.2021.695845/fullhttps://doaj.org/toc/2296-7745Erosion of cohesive sediments is a ubiquitous phenomenon in estuarine and intertidal environments. Several methods have been proposed to determine the surface erosion threshold (τc0), which are still debatable because of the numerous and uncertain definitions. Based on erosion microcosm experiments, we have compared three different methods using (1) eroded mass (EM), (2) erosion rate (ER), and (3) suspended sediment concentration (SSC), and suggested a suitable method for revealing the variation of erodibility in intertidal sediments. Erosion experiments using a microcosm system were carried out in the Muuido tidal flat, west coast of South Korea. The mean values of τc0 for three methods were: 0.20 ± 0.08 Pa (EM); 0.18 ± 0.07 Pa (ER); and (3) 0.17 ± 0.09 Pa (SSC). The SSC method yielded the lowest τc0, due to the outflow of suspended sediment from the erosion chamber of the microcosm. This was because SSC gradually decreased with time after depleting the erodible sediment at a given bed shear stress (τb). Therefore, the regression between SSC and applied τb might skew an x-intercept, resulting in the underestimation (or “not-determined”) of τc0. The EM method yielded robust and accurate (within the range of τb step at which erosion begins) results. The EM method represents how the erodible depth thickens as τb increases and therefore seems better suited than the SSC and ER methods for representing depth-limited erosion of cohesive sediments. Furthermore, this study identified the spatiotemporal variations of τc0 by EM method in an intertidal flat. The τc0 in mud flat was about two times higher than that in mixed flat. Compared to the end of tidal emersion, the sediment was 10–40% more erodible at the beginning stage.Hun Jun HaHo Kyung HaFrontiers Media S.A.articleerosion thresholdintertidal flatcohesive sedimentmethodsmicrocosm systemScienceQGeneral. Including nature conservation, geographical distributionQH1-199.5ENFrontiers in Marine Science, Vol 8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	erosion threshold intertidal flat cohesive sediment methods microcosm system Science Q General. Including nature conservation, geographical distribution QH1-199.5
spellingShingle	erosion threshold intertidal flat cohesive sediment methods microcosm system Science Q General. Including nature conservation, geographical distribution QH1-199.5 Hun Jun Ha Ho Kyung Ha Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System
description	Erosion of cohesive sediments is a ubiquitous phenomenon in estuarine and intertidal environments. Several methods have been proposed to determine the surface erosion threshold (τc0), which are still debatable because of the numerous and uncertain definitions. Based on erosion microcosm experiments, we have compared three different methods using (1) eroded mass (EM), (2) erosion rate (ER), and (3) suspended sediment concentration (SSC), and suggested a suitable method for revealing the variation of erodibility in intertidal sediments. Erosion experiments using a microcosm system were carried out in the Muuido tidal flat, west coast of South Korea. The mean values of τc0 for three methods were: 0.20 ± 0.08 Pa (EM); 0.18 ± 0.07 Pa (ER); and (3) 0.17 ± 0.09 Pa (SSC). The SSC method yielded the lowest τc0, due to the outflow of suspended sediment from the erosion chamber of the microcosm. This was because SSC gradually decreased with time after depleting the erodible sediment at a given bed shear stress (τb). Therefore, the regression between SSC and applied τb might skew an x-intercept, resulting in the underestimation (or “not-determined”) of τc0. The EM method yielded robust and accurate (within the range of τb step at which erosion begins) results. The EM method represents how the erodible depth thickens as τb increases and therefore seems better suited than the SSC and ER methods for representing depth-limited erosion of cohesive sediments. Furthermore, this study identified the spatiotemporal variations of τc0 by EM method in an intertidal flat. The τc0 in mud flat was about two times higher than that in mixed flat. Compared to the end of tidal emersion, the sediment was 10–40% more erodible at the beginning stage.
format	article
author	Hun Jun Ha Ho Kyung Ha
author_facet	Hun Jun Ha Ho Kyung Ha
author_sort	Hun Jun Ha
title	Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System
title_short	Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System
title_full	Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System
title_fullStr	Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System
title_full_unstemmed	Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System
title_sort	comparison of methods for determining erosion threshold of cohesive sediments using a microcosm system
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/007b2a21f79c4d3cb5520ec39eeb3888
work_keys_str_mv	AT hunjunha comparisonofmethodsfordeterminingerosionthresholdofcohesivesedimentsusingamicrocosmsystem AT hokyungha comparisonofmethodsfordeterminingerosionthresholdofcohesivesedimentsusingamicrocosmsystem
_version_	1718445190319964160

Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System

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