Jointed Source Rock and Fluvial Gravels Controlled by Rosin's Law: A Grain-Size Study in Calabria, South Italy

Ibbeken, Hillert

doi:10.1306/212f834b-2b24-11d7-8648000102c1865d

Cited by 9 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…4. less, we suggest that such fragmentation theory is applicable to understand and predict landslide GSD in a wide range of contexts, at least for rock, soil, and mixed avalanches and generally disrupted slides, which are the most commonly triggered (Keefer, 1984). Further, our observations suggest that Eq.…”

Section: The Importance Of Fragmentation and Source Materials Initial Grain Sizementioning

confidence: 74%

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

2021

View full text Add to dashboard Cite

Abstract. The size of grains delivered to rivers by hillslope processes is thought to be a key factor controlling sediment transport, long-term erosion and the information recorded in sedimentary archives. Recently, models have been developed to estimate the grain size distribution produced in soil, but these models may not apply to active orogens where high erosion rates on hillslopes are driven by landsliding. To date, relatively few studies have focused on landslide grain size distributions. Here, we present grain size distributions (GSDs) obtained by grid-by-number sampling on 17 recent landslide deposits in Taiwan, and we compare these GSDs to the geometrical and physical properties of the landslides, such as their width, area, rock type, drop height and estimated scar depth. All slides occurred in slightly metamorphosed sedimentary units, except two, which occurred in younger unmetamorphosed shales, with a rock strength that is expected to be 3–10 times weaker than their metamorphosed counterparts. For 11 landslides, we did not observe substantial spatial variations in the GSD over the deposit. However, four landslides displayed a strong grain size segregation on their deposit, with the overall GSD of the downslope toe sectors being 3–10 times coarser than apex sectors. In three cases, we could also measure the GSD inside incised sectors of the landslides deposits, which presented percentiles that were 3–10 times finer than the surface of the deposit. Both observations could be due to either kinetic sieving or deposit reworking after the landslide failure, but we cannot explain why only some deposits had strong segregation. Averaging this spatial variability, we found the median grain size of the deposits to be strongly negatively correlated with drop height, scar width and depth. However, previous work suggests that regolith particles and bedrock blocks should coarsen with increasing depth, which is the inverse of our observations. Accounting for a model of regolith coarsening with depth, we found that the ratio of the estimated original bedrock block size to the deposit median grain size (D50) of the deposit was proportional to the potential energy of the landslide normalized to its bedrock strength. Thus, the studied landslides agree well with a published, simple fragmentation model, even if that model was calibrated on rock avalanches with larger volume and stronger bedrock than those featured in our dataset. Therefore, this scaling may serve for future modeling of grain size transfer from hillslopes to rivers, with the aim to better understanding landslide sediment evacuation and coupling to river erosional dynamics.

show abstract

Section: The Importance Of Fragmentation and Source Materials Initial Grain Sizementioning

confidence: 74%

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

2021

View full text Add to dashboard Cite

show abstract

“…All distributions seem unimodal, except LS-16 with more than 40% of the grains finer than 2 mm, likely containing a second, sub-millimetric mode that could not be constrained by our methods. Grain size distributions can often be well described by a Weibull or Lognormal distribution (Ibbeken, 1983). For the studied landslides, eight GSDs are 5 better fit (according to both Kolmogorov-Smirnov and Anderson-Darling statistics, (Stephens, 1974)) by a Weibull distribution (LS 2s,3,4,5s,5i,6,9n,9o), while all others are better fit by a log-normal distribution (Fig 2).…”

Section: Landslide Grain Size Distributions and Their Internal Variabmentioning

confidence: 84%

“…In those settings, understanding and modeling the controls on landslide GSD should be an urgent goal, which has been addressed by few studies. Indeed, in contrast to river sediments for which many studies exist (e.g., Ibbeken, 1983;Whittaker et al, 2011;Chung and Chang, 2013;Guerit et al, 2014Guerit et al, , 2018 landslide GSDs have rarely been measured, in part because the latter is considerably more difficult, time consuming and potentially dangerous than the former.…”

Section: Introductionmentioning

confidence: 99%

Controls on the grain size distribution of landslides in Taiwan: the inﬂuence of drop height, scar depth and bedrock strength

Marc¹,

Turowski²,

Meunier³

2021

Preprint

View full text Add to dashboard Cite

Abstract. The size of grains delivered to river by hillslopes processes is thought to be a key factor to better understand sediment transport, long-term erosion as well as sedimentary archives. Recently, models have been developed for the grain size distribution produced in soil, but they may not apply to active orogens where high erosion rates on hillslopes are driven by landsliding. Until now relatively few studies have focused on landslide grain size distributions. Here we present grain size distribution 5 (GSD) obtained by the grid-by-number sampling on 17 recent landslide deposits in Taiwan, and we compare it to the geometrical and physical properties of the landslides, such as their width, area, rock-type, drop height and estimated depth. All slides occurred in slightly metamorphosed sedimentary units, except two, which occurred in younger unmetamorphosed shales, with rock strength expected to be 3 to 10 times weaker from their metamorphosed counterparts. We found that 4 deposits displayed a strong grain-size segregation on their deposit with downslope toe deposits 3 to 10 times coarser than apex 10 deposits. In 3 cases, we could also measure the GSD inside the landslides that presented percentiles 3 to 10 times finer than the surface of the deposit. Both observations could be due to either kinetic sieving or deposit reworking after the landslide failure but we cannot explain why only some deposits had a strong segregation. Averaging this spatial variability we found the median grainsize of the deposits to be strongly negatively correlated to drop height, scar width and depth. However, previous work suggest that regolith particles and bedrock blocks should coarsen with increasing depth, opposite to our observation. 15 Accounting for a model of regolith coarsening with depth, we found that the ratio of the original bedrock block size and the D50 was proportional the potential energy of the landslide normalized to its bedrock strength. Thus the studied landslides agree well with a published, simple fragmentation model, even if that model was calibrated on much larger and much stronger rock avalanches than those featured in our dataset. This scaling may thus serve for future model of grain size transfer from hillslopes to river, trying to better understand landslide sediment evacuation and coupling to river erosional dynamics.

show abstract

“…We conclude this section by underlining that more measurements, especially of source rock block size and strength, are needed to fully demonstrate the applicability of the fragmentation theory presented by Locat et al (2006). Neverthe- less, we suggest that such fragmentation theory is applicable to understand and predict landslide GSD in a wide range of contexts, at least for rock, soil, and mixed avalanches and generally disrupted slides, which are the most commonly triggered (Keefer, 1984). Further, our observations suggest that Eq.…”

Section: The Importance Of Fragmentation and Source Materials Initial Grain Sizementioning

confidence: 88%

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

Marc

Turowski

Meunier

2021

Preprint

View full text Add to dashboard Cite

<div>The size of grains delivered to rivers by hillslopes processes is thought to be a key factor to better understand sediment transport, long-term erosion as well as sedimentary archives. Recently, models have been developed for the grain size distribution produced in soils, but they may be irrelevant to active orogens where high erosion rates on hillslopes are driven by landsliding. Still, until now relatively few studies have focused on measuring and explaining the variability of landslide grain size distributions.</div><div>Here we present grain size distribution obtained by the grid-by-number method on 17 recent landslide deposits in Taiwan, and we compare it to the geometrical and physical properties of the landslides, such as their width, area, rock-type and strength, drop height and estimated depth. All landslides occurred in slightly metamorphosed sedimentary units, except two which occurred in younger unmetamorphosed shales, with rock strength expected to be 3 to 10 times weaker from their metamorphosed counterparts. We found that 4 deposits displayed a strong grain size segregation on their deposit with grains at the toe (downslope) of the deposit 3 to 10 times coarser than the one at the apex. In 3 cases, we could also measure the grain size distribution inside the landslides that presented percentiles 3 to 10 times finer than the surface of their deposits. Both observations could be due to either kinetic sieving or deposit reworking after the landslide failure but we could not explain why only some deposits had a strong segregation.</div><div>Averaging this spatial variability we found the median grain size (D50) of the deposits to be strongly negatively correlated to drop height, scar width and depth. However, previous work suggests that regolith particlesvand bedrock blocks should become coarser with increasing depth (Cohen et al., 2010; Clarke and Burbank, 2011), opposite to our observation. Accounting for a model of regolith coarsening with depth, we found that the ratio of the original bedrock blocksize and the D50 was proportional to the potential energy of the landslide normalized to its bedrock strength. Thus the studied landslides agree well with the simple fragmentation model from Locat et al. (2006), even if it was calibrated on much larger and much stronger rock avalanches. This scaling may thus serve for future model of grain size transfer from hillslopes to river, trying to better understand landslide sediment evacuation and the coupling between hillslopes and river erosional dynamic.</div><div>&#160;</div><div>References:</div><div> <div> <div>Clarke, B. A. and Burbank, D. W.: Quantifying bedrock-fracture patterns within the shallow subsurface: Implications for rock mass strength, bedrock landslides, and erodibility, Journal of Geophysical Research: Earth Surface, 116(F4), F04009, , 2011.</div> <div>Cohen, S., Willgoose, G. and Hancock, G.: The mARM3D spatially distributed soil evolution model: Three-dimensional model framework and analysis of hillslope and landform responses, Journal of Geophysical Research: Earth Surface, 115(F4), , 2010.</div> <div>Locat, P., Couture, R., Leroueil, S., Locat, J. and Jaboyedoff, M.: Fragmentation energy in rock avalanches, Canadian Geotechnical Journal, 43(8), 830&#8211;851, , 2006.</div> </div> </div><div>&#160;</div>

show abstract

Jointed Source Rock and Fluvial Gravels Controlled by Rosin's Law: A Grain-Size Study in Calabria, South Italy

Cited by 9 publications

References 0 publications

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

Controls on the grain size distribution of landslides in Taiwan: the inﬂuence of drop height, scar depth and bedrock strength

Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength

Contact Info

Product

Resources

About