scholarly journals Formation of levees, troughs and elevated channels by avalanches on erodible slopes

2017 ◽  
Vol 823 ◽  
pp. 278-315 ◽  
Author(s):  
A. N. Edwards ◽  
S. Viroulet ◽  
B. P. Kokelaar ◽  
J. M. N. T. Gray
Keyword(s):  
Risk Mitigation ◽  
Constant Width ◽  
Small Scale ◽  
Snow Avalanches ◽  
Erosion And Deposition ◽  
Friction Law ◽  
Slope Inclination ◽  
Deposit Surface ◽  
Rough Bed ◽  
Initial Deposit

Snow avalanches are typically initiated on marginally stable slopes with a surface layer of fresh snow that may easily be incorporated into them. The erosion of snow at the front is fundamental to the dynamics and growth of snow avalanches and they may rapidly bulk up, making them much more destructive than the initial release. Snow may also deposit at the rear, base and sides of the flow and the net balance of erosion and deposition determines whether an avalanche grows or decays. In this paper, small-scale analogue experiments are performed on a rough inclined plane with a static erodible layer of carborundum grains. The static layer is prepared by slowly closing down a flow from a hopper at the top of the slope. This leaves behind a uniform-depth layer of thickness $h_{stop}$ at a given slope inclination. Due to the hysteresis of the rough bed friction law, this layer can then be inclined to higher angles provided that the thickness does not exceed $h_{start}$, which is the maximum depth that can be held static on a rough bed. An avalanche is then initiated on top of the static layer by releasing a fixed volume of carborundum grains. Dependent on the slope inclination and the depth of the static layer three different behaviours are observed. For initial deposit depths above $h_{stop}$, the avalanche rapidly grows in size by progressively entraining more and more grains at the front and sides, and depositing relatively few particles at the base and tail. This leaves behind a trough eroded to a depth below the initial deposit surface and whose maximal areal extent has a triangular shape. Conversely, a release on a shallower slope, with a deposit of thickness $h_{stop}$, leads to net deposition. This time the avalanche leaves behind a levee-flanked channel, the floor of which lies above the level of the initial deposit and narrows downstream. It is also possible to generate avalanches that have a perfect balance between net erosion and deposition. These avalanches propagate perfectly steadily downslope, leaving a constant-width trail with levees flanking a shallow trough cut slightly lower than the initial deposit surface. The cross-section of the trail therefore represents an exact redistribution of the mass reworked from the initial static layer. Granular flow problems involving erosion and deposition are notoriously difficult, because there is no accepted method of modelling the phase transition between static and moving particles. Remarkably, it is shown in this paper that by combining Pouliquen & Forterre’s (J. Fluid Mech., vol. 453, 2002, pp. 133–151) extended friction law with the depth-averaged $\unicode[STIX]{x1D707}(I)$-rheology of Gray & Edwards (J. Fluid Mech., vol. 755, 2014, pp. 503–544) it is possible to develop a two-dimensional shallow-water-like avalanche model that qualitatively captures all of the experimentally observed behaviour. Furthermore, the computed wavespeed, wave peak height and stationary layer thickness, as well as the distance travelled by decaying avalanches, are all in good quantitative agreement with the experiments. This model is therefore likely to have important practical implications for modelling the initiation, growth and decay of snow avalanches for hazard assessment and risk mitigation.

scholarly journals Modelling erosion and deposition in geophysical granular mass flows

2021 ◽  
Vol 52 (1) ◽  
pp. 29-32
Author(s):  
Sylvain Viroulet ◽  
Chris Johnson ◽  
Nico Gray
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Pyroclastic Flows ◽  
Small Scale ◽  
Snow Avalanches ◽  
Erosion And Deposition ◽  
Granular Rheology ◽  
Scale Models ◽  
Mass Flows

During hazardous geophysical mass flows, such as rock or snow avalanches, debris flows and volcanic pyroclastic flows, a continuous exchange of material can occur between the slide and the bed. The net balance between erosion and deposition of particles can drastically influence the behaviour of these flows. Recent advances in describing the non-monotonic effective basal friction and the internal granular rheology in depth averaged theories have enabled small scale laboratory experiments (see fig. 1) to be quantitatively reproduced and can also be implemented in large scale models to improve hazard mitigation.

scholarly journals Effective friction law for small-scale fault heterogeneity in 3D dynamic rupture

2011 ◽  
Vol 116 (B10) ◽  
Author(s):  
S. Latour ◽  
M. Campillo ◽  
C. Voisin ◽  
I. R. Ionescu ◽  
J. Schmedes ◽  
...  
Keyword(s):  
Small Scale ◽  
Dynamic Rupture ◽  
Friction Law ◽  
Fault Heterogeneity ◽  
Effective Friction

scholarly journals Multifractal analysis of radar rainfall fields over the area of Rome

2005 ◽  
Vol 2 ◽  
pp. 293-299 ◽  
Author(s):  
G. Calenda ◽  
E. Gorgucci ◽  
F. Napolitano ◽  
A. Novella ◽  
E. Volpi
Keyword(s):  
Scale Invariance ◽  
Large Scale ◽  
Doppler Radar ◽  
Risk Mitigation ◽  
Small Scale ◽  
Radar Rainfall ◽  
Invariance Properties ◽  
Meteorological Radar ◽  
Using Data ◽  
Precipitation Events

Abstract. A scale-invariance analysis of space and time rainfall events monitored by meteorological radar over the area of Rome (Italy) is proposed. The study of the scale-invariance properties of intense precipitation storms, particularly important in flood forecast and risk mitigation, allows to transfer rainfall information from the large scale predictive meteorological models to the small scale hydrological rainfall-runoff models. Precipitation events are monitored using data collected by the polarimetric Doppler radar Polar 55C (ISAC-CNR), located 15 km Southeast from downtown. The meteorological radar provides the estimates of rainfall intensity over an area of about 10 000 km2 at a resolution of 2×2 km2 in space and 5 min in time. Many precipitation events have been observed from autumn 2001 up to now. A scale-invariance analysis is performed on some of these events with the aim at exploring the multifractal properties and at understanding their dependence on the meteorological large-scale conditions.

scholarly journals Revisiting currency swaps: hedging real estate investments in global city markets

2018 ◽  
Vol 36 (2) ◽  
pp. 191-209
Author(s):  
Philipp Bejol ◽  
Nicola Livingstone
Keyword(s):  
Real Estate ◽  
Foreign Currency ◽  
Risk Mitigation ◽  
Sampling Technique ◽  
Real Estate Market ◽  
Small Scale ◽  
Negative Consequences ◽  
Content Type ◽  
Net Worth ◽  
Individual Asset

Purpose The purpose of this paper is to re-examine currency swaps as an effective hedging technique for individual asset performance in today’s global real estate market, by considering hypothetical prime office investments across six different cities and five currency pairs. The perspective of a risk-averse, high net worth, non-institutional, smaller-scale Swiss investor is paired with investors from five additional national markets. Design/methodology/approach The study examines currency swaps in key office markets across three continents (Frankfurt, London, New York, Sydney, Warsaw and Zurich) and extends previous work on the topic by adopting both Monte Carlo (MC) and Latin Hypercube (LH) techniques to create stochastic samples for individual asset performance analyses. This is the first paper to apply LH sampling to currency swaps with underlying real estate assets, and the validity of this method is compared with that of MC. Four models are presented: the experience of the domestic investor (no exchange rate (ER) fluctuations); an unhedged direct foreign investment; hedging rental income and initial purchase price via a currency swap; and hedging rental income and anticipated terminal value. Findings The efficacy of a swap depends on the historical framework of the ERs. If the foreign currency depreciates against the domestic one, hedging the repatriated cash flow of a property investment proved superior to the unhedged strategy (EUR, GBP, PLN and USD to the CHF). An investor would benefit from exposure to an appreciating foreign currency (CHF to the EUR, GBP, PLN and USD), with an unhedged strategy clearly outperforming the currency swap as well as the domestic investor’s performance, while a historically sideways fluctuating ER (AUD to the CHF) also favours an unhedged approach. In all scenarios, unexpected economic or market shocks could cause negative consequences on the repatriated proceeds. Practical implications This research is of interest to small-scale, non-institutional investors aiming to develop strategies for currency risk mitigation in international investments for individual assets; however, tax-optimising strategies and the implications on a larger portfolio have not been taken into account. Originality/value There is no recent academic work on the efficacy of currency swaps in today’s global office market, nor has the position of smaller-scale high net worth investors received much academic attention. This research revisits the discussion on their validity, providing contemporary insight into the performance of six markets using LH as an alternative and original sampling technique.

scholarly journals Scale Modeling of Snow–Avalanche Impact on Structures

1980 ◽  
Vol 26 (94) ◽  
pp. 189-196
Author(s):  
T. E. Lang ◽  
J.D. Dent
Keyword(s):  
Froude Number ◽  
Computer Modeling ◽  
Snow Avalanche ◽  
Small Scale ◽  
Snow Avalanches ◽  
Scale Modeling ◽  
Impact Processes ◽  
Model Fluid ◽  
Impact Predictions

AbstractSmall–scale modeling of flow and impact of snow avalanches is demonstrated to be both feasible and accurate. Geometric, kinematic, and force variables are scaled correctly under equivalence of Froude number between prototype and model using sifted snow as the model fluid. Physical and computer–simulated impact processes show correspondence, so that computer modeling is demonstrated to be a viable tool in flow and impact predictions.

scholarly journals Prevalence and risk factors associated with Campylobacter spp. and Salmonella enterica in livestock raised on diversified small-scale farms in California

2019 ◽  
Vol 147 ◽  
Author(s):  
A. F. A. Pires ◽  
L. Patterson ◽  
E. A. Kukielka ◽  
P. Aminabadi ◽  
N. Navarro-Gonzalez ◽  
...  
Keyword(s):  
Risk Factors ◽  
Salmonella Enterica ◽  
Management Practices ◽  
Risk Mitigation ◽  
Significant Risk ◽  
Mitigation Strategies ◽  
Farm Size ◽  
Small Scale ◽  
Animal Products ◽  
Factors Associated

Abstract Diversified farms are operations that raise a variety of crops and/or multiple species of livestock, with the goal of utilising the products of one for the growth of the other, thus fostering a sustainable cycle. This type of farming reflects consumers' increasing demand for sustainably produced, naturally raised or pasture-raised animal products that are commonly produced on diversified farms. The specific objectives of this study were to characterise diversified small-scale farms (DSSF) in California, estimate the prevalence of Salmonella enterica and Campylobacter spp. in livestock and poultry, and evaluate the association between farm- and sample-level risk factors and the prevalence of Campylobacter spp. on DSSF in California using a multilevel logistic model. Most participating farms were organic and raised more than one animal species. Overall Salmonella prevalence was 1.19% (95% confidence interval (CI95) 0.6–2), and overall Campylobacter spp. prevalence was 10.8% (CI95 = 9–12.9). Significant risk factors associated with Campylobacter spp. were farm size (odds ratio (OR)10–50 acres: less than 10 acres = 6, CI95 = 2.11–29.8), ownership of swine (OR = 9.3, CI95 = 3.4–38.8) and season (ORSpring: Coastal summer = 3.5, CI95 = 1.1–10.9; ORWinter: Coastal summer = 3.23, CI95 = 1.4–7.4). As the number of DSSF continues to grow, evaluating risk factors and management practices that are unique to these operations will help identify risk mitigation strategies and develop outreach materials to improve the food safety of animal and vegetable products produced on DSSF.

scholarly journals Geochemical and Sr–Nd isotopic features of the Zaro volcanic complex: insights on the magmatic processes triggering a small-scale prehistoric eruption at Ischia island (south Italy)

2020 ◽  
Vol 109 (8) ◽  
pp. 2829-2849
Author(s):  
C. Pelullo ◽  
G. Cirillo ◽  
R. S. Iovine ◽  
I. Arienzo ◽  
M. Aulinas ◽  
...  
Keyword(s):  
Risk Mitigation ◽  
Mafic Magma ◽  
Small Scale ◽  
Volcanic Complex ◽  
Magmatic System ◽  
Mafic Enclaves ◽  
South Italy ◽  
Ischia Island ◽  
Magmatic Processes ◽  
Trace Element Contents

Abstract The prehistoric (< 7 ka) Zaro eruption at Ischia island (Southern Italy) produced a lava complex overlaying a pyroclastic deposit. Although being of low energy, the Zaro eruption might have caused casualties among the neolithic population that inhabited that area of Ischia, and damages to their settlements. A similar eruption at Ischia with its present-day population would turn into a disaster. Therefore, understanding the magmatic processes that triggered the Zaro eruption would be important for volcanic hazard assessment and risk mitigation, so as to improve a knowledge that can be applied to other active volcanic areas worldwide. The main Zaro lava body is trachyte and hosts abundant mafic and felsic enclaves. Here all juvenile facies have been fully characterized from petrographic, geochemical and isotopic viewpoints. The whole dataset (major and trace element contents; Sr–Nd isotopic composition) leads to rule out a genetic link by fractional crystallization among the variable facies. Thus, we suggest that the Zaro mafic enclaves could represent a deep-origin mafic magma that mingled/mixed with the main trachytic one residing in the Ischia shallow magmatic system. The intrusion of such a mafic magma into a shallow reservoir filled by partly crystallized, evolved magma could have destabilized the magmatic system presumably acting as a rapid eruption trigger. The resulting processes of convection, mixing and rejuvenation have possibly played an important role in pre- and syn-eruptive phases also in several eruptions of different sizes in the Neapolitan area and elsewhere in the world.

scholarly journals Basics of Good Business Plan for Small-Scale Agribusiness Investors in Nigeria

2021 ◽  
Author(s):  
Mustapha Momoh ◽  
Caroline Aturu-Aghedo ◽  
Nana Usman Bature
Keyword(s):  
Risk Mitigation ◽  
Cost Savings ◽  
High Rate ◽  
Small Scale ◽  
Management Skills ◽  
Business Skills ◽  
Job Experience ◽  
Agriculture Sector ◽  
Entrepreneurial Skills ◽  
The Face

This chapter provides a synthesis of planning small-scale entrepreneurial skills to guide the current and prospective micro investors to harness wide ranges of agribusiness value chains in Nigeria. This initiative considered alternatives in business strategic options to harness the potentials therein, which involve production, distribution, processing of agricultural products and services integration for converting agricultural outputs for regular and timely supply of domestic and international needs. The current outcry for economic diversification couple with high rate of unemployment in Nigeria requires concerted efforts to boost the agriculture sector as a viable alternative for growth and development. Suffices to say, most agribusiness investors more often than not, experience failure because of the dearth of requisite business skills for planning the survival and growth of small-scale agribusinesses in the face of modern realities. In this wise, the chapter brings the benefits such as risk mitigation, cost savings, and income generation through combination of known production planning and business management skills. The chapter adopts discursive taxonomy, interpolating elicited facts from available literature plus the knowledge of ‘on-the-job-experience’ to promote and support the development of agribusinesses strategy for the transformation of the agriculture sector to generate employment, income, and promote food security, and competitiveness in the marketplaces.

scholarly journals Optimal design under uncertainty of a passive defense structure against snow avalanches: from a general Bayesian framework to a simple analytical model

2008 ◽  
Vol 8 (5) ◽  
pp. 1067-1081 ◽  
Author(s):  
N. Eckert ◽  
E. Parent ◽  
T. Faug ◽  
M. Naaim
Keyword(s):  
Granular Media ◽  
Bayesian Framework ◽  
Simple Relation ◽  
Small Scale ◽  
Snow Avalanches ◽  
Runout Distance ◽  
Risk Functions ◽  
Peak Over Threshold ◽  
Simplifying Assumptions ◽  
Modelling Assumptions

Abstract. For snow avalanches, passive defense structures are generally designed by considering high return period events. In this paper, taking inspiration from other natural hazards, an alternative method based on the maximization of the economic benefit of the defense structure is proposed. A general Bayesian framework is described first. Special attention is given to the problem of taking the poor local information into account in the decision-making process. Therefore, simplifying assumptions are made. The avalanche hazard is represented by a Peak Over Threshold (POT) model. The influence of the dam is quantified in terms of runout distance reduction with a simple relation derived from small-scale experiments using granular media. The costs corresponding to dam construction and the damage to the element at risk are roughly evaluated for each dam height-hazard value pair, with damage evaluation corresponding to the maximal expected loss. Both the classical and the Bayesian risk functions can then be computed analytically. The results are illustrated with a case study from the French avalanche database. A sensitivity analysis is performed and modelling assumptions are discussed in addition to possible further developments.

scholarly journals Climate warming enhances snow avalanche risk in the Western Himalayas

2018 ◽  
Vol 115 (13) ◽  
pp. 3410-3415 ◽  
Author(s):  
J. A. Ballesteros-Cánovas ◽  
D. Trappmann ◽  
J. Madrigal-González ◽  
N. Eckert ◽  
M. Stoffel
Keyword(s):  
Climate Warming ◽  
Risk Mitigation ◽  
Terrestrial Ecosystems ◽  
Well Being ◽  
Mitigation Strategies ◽  
Snow Avalanche ◽  
Western Himalayas ◽  
Snow Avalanches ◽  
Study Region ◽  
Indian Himalayas

Ongoing climate warming has been demonstrated to impact the cryosphere in the Indian Himalayas, with substantial consequences for the risk of disasters, human well-being, and terrestrial ecosystems. Here, we present evidence that the warming observed in recent decades has been accompanied by increased snow avalanche frequency in the Western Indian Himalayas. Using dendrogeomorphic techniques, we reconstruct the longest time series (150 y) of the occurrence and runout distances of snow avalanches that is currently available for the Himalayas. We apply a generalized linear autoregressive moving average model to demonstrate linkages between climate warming and the observed increase in the incidence of snow avalanches. Warming air temperatures in winter and early spring have indeed favored the wetting of snow and the formation of wet snow avalanches, which are now able to reach down to subalpine slopes, where they have high potential to cause damage. These findings contradict the intuitive notion that warming results in less snow, and thus lower avalanche activity, and have major implications for the Western Himalayan region, an area where human pressure is constantly increasing. Specifically, increasing traffic on a steadily expanding road network is calling for an immediate design of risk mitigation strategies and disaster risk policies to enhance climate change adaption in the wider study region.

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