A data-driven fuzzy approach to simulate the critical shear stress of mixed cohesive/non-cohesive sediments

Silva, Aline Schäfer Rodrigues; Noack, Markus; Schlabing, Dirk; Wieprecht, Silke

doi:10.1007/s11368-017-1860-8

Cited by 6 publications

(6 citation statements)

References 23 publications

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“…In general, the spatio‐temporal erosion variability indicates that the distribution of the erosion is right‐skewed and not normally distributed for all considered time steps and over all experiments (Figure 12 and Table 4). This corresponds to the general understanding of cohesive sediment erosion, since locally increased erosion is likely due to the mutual interference of surface changes and flow changes initiating progressing erosion (as confirmed by the detected processes (iii) and (iv) shown in Figures 8–10) (see also Van Prooijen and Winterwerp, 2010; Schäfer Rodrigues Silva et al ., 2018). More specifically, the (now quantifiable) variability indicates that the deepening can vary significantly during temporal progression.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…Overall, it can be concluded that the erosion decreased over depth (Figures 5 and 11) and thus with a higher bulk density, a refinement of the sediment composition, and a decreasing organic content (Table 2). This is in general agreement with previous knowledge on the erosion stability of natural non‐cohesive/cohesive sediment mixtures (McNeil et al ., 1996; Lick and McNeil, 2001; Righetti and Lucarelli, 2007; Schäfer Rodrigues Silva et al ., 2018).…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…Further, the non‐uniformity of natural sediments results in variable bed shear strength and, in combination with the turbulent characteristic of flow, a random behaviour is induced during erosion (e.g. Van Prooijen and Winterwerp, 2010; Schäfer Rodrigues Silva et al ., 2018).…”

Section: Introductionmentioning

confidence: 99%

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High spatio‐temporal resolution measurements of cohesive sediment erosion

Beckers

Inskeep

Haun

et al. 2020

Earth Surf Processes Landf

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In this study, we present a novel approach to measure fundamental processes of cohesive sediment erosion. The experimental setup consists of a laboratory erosion flume (SETEG) and a photogrammetric method to detect sediment erosion (PHOTOSED). Detailed data are presented for three erosion experiments, which were conducted with a natural non‐cohesive/cohesive sediment mixture at increasing sediment depths (4, 8, 16 cm). In each experiment, the sediment was exposed to a set of incrementally increasing shear stresses and the erosion was measured dynamically, pixel‐based, and approximate to the process scale given the resolution of PHOTOSED. This enables us to distinguish between (i) individual emerging erosion spots caused by surface erosion and (ii) large holes torn open by detached aggregate chunks. Moreover, interrelated processes were observed, such as (iii) propagation of the erosion in the longitudinal and lateral direction leading to merging of disconnected erosion areas and (iv) progressive vertical erosion of already affected areas. By complementing the (bulk) erosion volume profiles with additional quantitative variables, which contain spatial information (erosion area, specific deepening, number of disconnected erosion areas), conclusions on the erosion behaviour (and the dominant processes) can be drawn without requiring qualitative information (such as visual observations). In addition, we provide figures indicating the spatio‐temporal erosion variability and the (bulk) erosion rates for selected time periods. We evaluate the variability by statistical quantities and show that significant erosion is mainly confined to only a few events during temporal progression, but then considerably exceeds the time‐averaged median of the erosion (factors between 7.0 and 16.0). Further, we point to uncertainties in using (bulk) erosion rates to assess cohesive sediment erosion and particularly the underlying processes. As a whole, the results emphasise the need to measure cohesive sediment erosion with high spatio‐temporal resolution to obtain reliable and robust information. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Section: Discussion Of Resultsmentioning

confidence: 99%

Section: Discussion Of Resultsmentioning

confidence: 99%

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High spatio‐temporal resolution measurements of cohesive sediment erosion

Beckers

Inskeep

Haun

et al. 2020

Earth Surf Processes Landf

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“…However, the inclusion of gas and water plays an important role during consolidation, as well as the ongoing production of gas within the deposits (e.g., Peeters et al, 2019). Although the detailed processes of consolidation are not yet clear, consolidation effects may result in higher shear strength of the sediments by reducing their porosity and permeability (Gerbersdorf & Wieprecht, 2015; Harb, 2013; Mehta et al, 1989; Schäfer Rodrigues Silva et al, 2018). Although laboratory studies exist (e.g., Torfs et al, 1996; Van Rijn & Barth, 2019), detailed large‐scale in situ measurements of for example bulk density or porosity are challenging and are often only performed with limited spatial resolution (Beckers et al, 2018; Blomqvist, 1985; Dück et al, 2019; McIntyre, 1971).…”

Section: Research Needs In Investigating Hydro‐morphological Processesmentioning

confidence: 99%

“…Black & Paterson (1997) provided an overview on existing in situ devices to investigate cohesive sediments, where in general two groups exist, namely benthic flumes and miscellaneous devices (Aberle, 2008; Aberle et al, 2017). However, all devices are characterised by limited spatial resolution and often provide only the possibility of quantifying erosion thresholds of cohesive/non‐cohesive sediment mixtures, without providing additional knowledge regarding the resuspension of cohesive sediments (e.g., by Beckers et al, 2020; Berlamont et al, 1993; Gerbersdorf et al, 2007; Kamphuis & Hall, 1983; Mehta et al, 1989; Noack et al, 2015; Shao & Lu, 2000; Schäfer Rodrigues Silva et al, 2018).…”

Section: Research Needs In Investigating Hydro‐morphological Processesmentioning

confidence: 99%

Advanced methods to investigate hydro‐morphological processes in open‐water environments

Haun

Dietrich

2021

Earth Surf Processes Landf

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Hydro‐morphology describes the interactions between water and sediments in fluvial systems and the corresponding processes across all spatial and temporal scales. The results are natural and anthropogenically influenced bed structures and fluvial landforms. However, many of these hydro‐morphological processes cannot be described analytically yet, as a result of their stochastic behaviour and the multitude of processes involved across spatial and temporal scales. Deeper knowledge of these processes is essential, not only for understanding the system itself, but also for practical applications, which rely on correct and reliable investigations of these processes. During the European Geoscience Union (EGU) General Assembly (GA) 2018 in Vienna, Austria, the conveners of the session on “Measurements, monitoring and numerical modelling of sedimentary and hydro‐morphological processes in open‐water environments” had the idea of initiating a special issue, containing a collection of recent achievements in this research field. The aim of this extended introduction is twofold. First, an overview on research needs in investigating hydro‐morphological processes in open‐water environments is given in this article. Second, recently published studies that aim to improve the understanding of hydro‐morphological processes in rivers, lakes and reservoirs by innovative measurement approaches are discussed. In addition to submitted papers collected from the EGU GA in 2017, 2018 and 2019, related studies published in Earth Surface Processes and Landforms (ESPL) over the last two years are also incorporated into this special issue. The papers selected cover a wide range of studies with differing spatial and temporal resolutions. This broad spectrum of different scales clearly indicates the challenges associated with the development and use of advanced methods for investigating hydro‐morphological processes in open‐water environments.

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