Challenges in slope stability assessment of contaminated fibrous sediments along the northern Baltic coast of Sweden

Löfroth, Hjördis; OʹRegan, Matt; Snowball, Ian; Holmén, Martin; Kopf, Achim J; Göransson, Gunnel; Hedfors, Jim; Apler, Anna; Frogner-Kockum, Paul

doi:10.1016/j.enggeo.2021.106190

Cited by 2 publications

(9 citation statements)

References 26 publications

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“…This observation shows that the resuspended fibers are thus of sufficiently low density to stay in suspension, disperse by currents and not settle until they reach calmer areas outside the fiberbank. Further, laboratory studies on particles obtained from two fiberbanks in the study area also indicate low settling velocities and indicate that the density of the pulp fibers is similar to the density of water (Löfroth et al, 2021). Figures 5, 6 show two photos of the fiberbank and fiberbank material at Väja.…”

Section: Field and Laboratory Measurementsmentioning

confidence: 81%

“…An interbedded coarse-grained layer was detected about 1-2 m down into the minerogenic sediment. The geotechnical investigation indicates that this layer has higher permeability and higher porewater pressure than the surrounding sediments (Löfroth et al, 2021).…”

Section: Field and Laboratory Measurementsmentioning

confidence: 95%

“…All field measurements are presented in Apler et al (2014Apler et al ( , 2019Apler et al ( , 2020, Dahlberg et al (2020), Dahlberg et al (2021), andLöfroth et al (2021).…”

Section: Field and Laboratory Measurementsmentioning

confidence: 99%

“…Geological and geotechnical surveys (2015 and 2017) show that the fiberbank is underlain by a thin layer of bark on top of a clayey silt, followed deeper down by laminated black-gray clayey silts that transition toward the base into glaciomarine varved clay (Löfroth et al, 2021). An interbedded coarse-grained layer was detected about 1-2 m down into the minerogenic sediment.…”

Section: Field and Laboratory Measurementsmentioning

confidence: 99%

“…For example, the high organic cellulose fiber content and their characteristics made it difficult to assess parameters like critical shear stresses, grain size distribution and bed surface roughness, which are parameters commonly included in formulas for sediment transport. It was also challenging to conduct proper geotechnical measurements of the fiberbank, for example to collect undisturbed core samples of the soft unconsolidated fibrous sediment and the underlying strata (Löfroth et al, 2021). The varves (thin silt and clay layers) in the underlying soft clay made trimming of specimens for laboratory tests challenging (Löfroth et al, 2021).…”

Section: The Case Studymentioning

confidence: 99%

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Assessing the Risk of Contaminant Dispersion From Fibrous Sediments of Industrial Origin

et al. 2021

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Unregulated discharges of wastewater from pulp and paper factories resulted in the formation of relatively thick organic (cellulose) rich sediments in shallow waters along the Swedish coast. These deposits are known as fiberbanks and are contaminated by persistent organic pollutants (POPs), metals and methylmercury, which can be dispersed by diffusion and advective processes coupled to propeller wash, high river discharges, strong wind waves and submarine landslides. Based on a case study of polychlorinated biphenyls (PCBs), one group of prevalent POPs in the fiberbanks, we present a probabilistic approach to estimate the potential risk of dispersion of fiberbank contaminants. The approach allows for estimation of the dispersal pathways that dominates the risk within a given time and provides more insight about the significance of various dispersion processes. We show that it is highly likely that chemical diffusion and advection triggered by ship-induced resuspension will disperse PCBs (sum of seven congeners; Σ7PCB) above a threshold level for environmental impact, while the likelihood of river and wind-wave generated resuspension dispersion pathways are lower (∼20%, respectively). We further show that there is approximately 5% likelihood that a submarine landslide will disperse Σ7PCB above the threshold level. The study implies that the governing parameters for risk assessment specifically should include reliable data on contaminant concentration, water depth above the fiberbank, estimation of concerned fiberbank areas, time duration of erosive fluid flows and measured diffusion. The approach provides insight into the importance of various dispersion processes. We suggest that it can be applied to support risk assessment, especially when there are limited available data and/or knowledge about the system under study.

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Section: Field and Laboratory Measurementsmentioning

confidence: 81%

Section: Field and Laboratory Measurementsmentioning

confidence: 95%

“…All field measurements are presented in Apler et al (2014Apler et al ( , 2019Apler et al ( , 2020, Dahlberg et al (2020), Dahlberg et al (2021), andLöfroth et al (2021).…”

Section: Field and Laboratory Measurementsmentioning

confidence: 99%

Section: Field and Laboratory Measurementsmentioning

confidence: 99%

Section: The Case Studymentioning

confidence: 99%

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Assessing the Risk of Contaminant Dispersion From Fibrous Sediments of Industrial Origin

et al. 2021

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Assessing the effectiveness of landslide slope stability by analysing structural mitigation measures and community risk perception

et al. 2023

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Rainfall-induced landslides seriously threaten hilly environments, leading local authorities to implement various mitigation measures to decrease disaster risk. However, there is a significant gap in the current literature regarding evaluating their effectiveness and the associated community risk perception. To address this gap, we used an interdisciplinary and innovative approach to analyse the slope stability of landslides, evaluate the effectiveness of existing structural mitigation measures, and assess the risk perception of those living in danger zones. Our case study focused on the Kutupalong Rohingya Camp (KRC) in Cox’s Bazar, Bangladesh, which is home to over one million Rohingya refugees from Myanmar. Although various structural and non-structural countermeasures were implemented in the KRC to mitigate the impact of landslides, many of them failed to prevent landslides from occurring. We utilised a variety of methods from the physical sciences, including the infinite slope, limit equilibrium (LEM), and finite element (FEM) approaches, to calculate the factor of safety (FoS) for specific slopes. Additionally, in the social sciences domain, we conducted a questionnaire survey of approximately 400 Rohingya participants to assess the community’s perception of the interventions and the degree of disaster risk. Our findings indicated that slopes with a gradient greater than 40° were unstable (FoS < 1), which was present throughout the entire KRC area. The effectiveness of the LEM and FEM methods was evaluated for four dominant slope angles (40°, 45°, 50°, and 55°) under varying loads (0, 50, and 100 kN/m2). The slopes were found to be stable for lower slope angles but unstable for higher slope angles (> 50°) and increased overburden loads (50–100 kN/m2). Different mitigation measures were tested on the identified unstable slopes to assess their effectiveness, but the results showed that the countermeasures only provided marginal protection against landslides. Survey results revealed that at least 70% of respondents believed that concrete retaining walls are more effective in reducing landslide occurrence compared to other measures. Additionally, about 60% of the respondents questioned the reliability of the existing structural mitigation measures. The study also found that the cohesion and friction angle of lower sandstone and the cohesion of upper soil layers are important factors to consider when designing and implementing slope protection countermeasures in the KRC area.

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Challenges in slope stability assessment of contaminated fibrous sediments along the northern Baltic coast of Sweden

Cited by 2 publications

References 26 publications

Assessing the Risk of Contaminant Dispersion From Fibrous Sediments of Industrial Origin

Assessing the Risk of Contaminant Dispersion From Fibrous Sediments of Industrial Origin

Assessing the effectiveness of landslide slope stability by analysing structural mitigation measures and community risk perception

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