Gully head modelling: A Mediterranean badland case study          下载免费PDF全文

Dino Torri  Jean Poesen  Mauro Rossi  Valerio Amici  Daniele Spennacchi  Cati Cremer 《地球表面变化过程与地形》2018,43(12):2547-2561

Predicting the location of gully heads in various environments is an important step towards predicting gully erosion rates. So far, field data collection and modelling of topographic thresholds for gully head development has mainly focused on gullies that formed in forested areas, rangelands, pastures and cropland. Such information for gullies in badlands however is very scarce. Therefore, this paper aims to extend the database on gully head topographical thresholds through data collection in a badland area and to improve the prediction of gully heads forming at sites with a very low erosion resistance value. For this, we chose a badland site located in central Italy that is characterized by biancana forms and both active and dormant gullies. The definition of the conditions under which present‐day gully heads developed allowed a better modelling of the gully head threshold equation, with modification of a previous model and the exemplification of how to use the updated model. The model shows that the resistance to gully head retreat depends on slope gradient and drainage area at gully heads, land use at the moment of gully development (as numerically expressed using parameters derived from the Runoff Curve Number method), surface rock fragment cover, presence of joints, pipes, and factors/processes affecting detachment rate. This study attempted to better understand environmental conditions that control the development of gully heads in badlands through a combination of field data collection of gully heads, an analysis of land use changes over 10 centuries, focusing on the period 1820–2005, and land use management through repeat photography and a critical examination of historical documents. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Climatic and structural controls on Late-glacial and Holocene rockfall occurrence in high-elevated rock walls of the Mont Blanc massif (Western Alps)     

Xavi Gallach  Julien Carcaillet  Ludovic Ravanel  Philip Deline  Christophe Ogier  Magali Rossi  Emmanuel Malet  David Garcia-Sellés 《地球表面变化过程与地形》2020,45(13):3071-3091

In the Mont Blanc massif (European Western Alps), rockfalls are one of the main natural hazards for alpinists and infrastructure. Rockfall activity after the Little Ice Age is well documented. An increase in frequency during the last three decades is related to permafrost degradation caused by rising air temperatures. In order to understand whether climate exerts a long-term control on rockfall occurrence, a selection of paleo-rockfall scars was dated in the Glacier du Géant basin [>3200 m above sea level (a.s.l.)] using terrestrial cosmogenic nuclides. Rockfall occurrence was compared to different climatic and glacial proxies. This study presents 55 new samples (including replicates) and 25 previously-published ages from nine sampling sites. In total, 62 dated rockfall events display ages ranging from 0.03 ± 0.02 ka to 88.40 ± 7.60 ka. Holocene ages and their uncertainties were used to perform a Kernel density function into a continuous dataset displaying rockfall probability per 100 years. Results highlight four Holocene periods of enhanced rockfall occurrence: (i) c. 7–5.7 ka, related to the Holocene Warm Periods; (ii) c. 4.5–4 ka, related to the Sub-boreal Warm Period; (iii) c. 2.3–1.6 ka, related to the Roman Warm Period; and (iv) c. 0.9–0.3 ka, related to the Medieval Warm Period and beginning of the Little Ice Age. Laser and photogrammetric three-dimensional (3D) models of the rock walls were produced to reconstruct the detached volumes from the best-preserved rockfall scars (≤0.91 ± 0.12 ka). A structural study was carried out at the scale of the Glacier du Géant basin using aerial photographs, and at the scale of four selected rock walls using the 3D models. Two main vertical and one horizontal fracture sets were identified. They correspond respectively to alpine shear zones and veins opened-up during long-term exhumation of the Mont Blanc massif. Our study confirms that climate primarily controls rockfall occurrence, and that structural settings, coincident at both the massif and the rock wall scales, control the rock-wall shapes as well as the geometry and volume of the rockfall events. © 2020 John Wiley & Sons, Ltd.  相似文献   

Biosedimentary record of postglacial coastal dynamics: high‐resolution sequence stratigraphy from the northern Tuscan coast (Italy)     

Alessandro Amorosi  Veronica Rossi  Daniele Scarponi  Stefano Claudio Vaiani  Anupam Ghosh 《Boreas: An International Journal of Quaternary Research》2014,43(4):939-954

Integrating analysis of the benthic palaeoecological record with multivariate ordination techniques represents a powerful synergy able to provide an improved characterization of coastal depositional facies in a sequence stratigraphical perspective. Through quantitative analysis of benthic foraminifer, ostracod and mollusc associations from the postglacial succession of Core M3 (Arno coastal plain, Tuscany, Italy), and application of detrended correspondence analysis (DCA) to the mollusc sub‐data set, we offer a refined picture of stratigraphical variations in faunal content from a paralic depositional setting, and reconstruct the palaeoenvironmental gradients that account for such variations. Despite distinct ecological behaviours, and taphonomic and sedimentological constraints, a strong ecological control on meio‐ and macrofaunal biofacies and taxa turnover is documented across the study succession. Amongst all possible mechanisms that may play a role in ‘shaping’ fossil distribution, the ecological signal driven by salinity represents the most prominent factor controlling the composition of fossil associations in the cored succession. Molluscs can even provide outstanding quantitative estimates of palaeosalinity along the sampled core. When plotted stratigraphically, the three fossil sub‐data sets show consistent patterns of vertical evolution that enable prompt identification of the key surfaces for sequence stratigraphical interpretation in otherwise lithologically indistinguishable deposits. The concomitant maximum richness of species with strong marine affinity, paralleled by the highest DCA salinity estimates, allows recognition of the maximum flooding zone, dated to ～7.7 cal. ka BP, within a homogeneous succession of outer lagoon clays. These clays are sandwiched between early transgressive, swamp to inner lagoon deposits and overlying prograding coastal?alluvial plain facies.  相似文献   

Degradation and Detoxification of Chlorophenols in Continuous‐Flow Fixed‐Bed Aerobic Reactors     

Alfredo Gallego  Virginia L. Gemini  Susana L. Rossi  Carlos E. Gómez  Gustavo D. Bulus Rossini  Sonia E. Korol 《洁净——土壤、空气、水》2011,39(8):774-780

An indigenous bacterial strain of Delftia sp. capable of degrading 2,4‐dicholorophenol and an indigenous bacterial community that degrades 2,4,6‐trichlorophenol (TCP) were employed to inoculate continuous down‐flow fixed‐bed reactors. Continuous‐reactors were constructed from PVC employing hollow PVC cylinders as support material. Synthetic wastewater was prepared by dissolving the corresponding chlorophenol in non‐sterile groundwater. Biodegradation was evaluated by spectrophotometry, chloride release, GC, and microbial growth. Detoxification was evaluated by using Daphnia magna as test organism. Delftia sp. was able to remove an average of 95.6% of DCP. Efficiency in terms of chemical oxygen demand (COD) was of 88.9%. The indigenous bacterial community that degrades TCP reached an average efficiency of 96.5 and 91.6% in terms of compound and COD removal, respectively. In both cases stoichiometric removal of chloride and detoxification was achieved. When synthetic wastewater feed was cut off for 7 days, both reactors showed a fast recovery after inflow restarting, reaching average outlet concentration values within 36 h. The promising behavior of the microorganisms and the low cost of the reactors tested allow us to suggest their possible application to remediation processes.  相似文献   

Natural highways for end-of-life solutions in the LEO region     

Elisa Maria Alessi  Giulia Schettino  Alessandro Rossi  Giovanni B. Valsecchi 《Celestial Mechanics and Dynamical Astronomy》2018,130(5):34

We present the main findings of a dynamical mapping performed in the Low Earth Orbit region. The results were obtained by propagating an extended grid of initial conditions, considering two different epochs and area-to-mass ratios, by means of a singly averaged numerical propagator. It turns out that dynamical resonances associated with high-degree geopotential harmonics, lunisolar perturbations and Solar radiation pressure can open natural deorbiting highways. For area-to-mass ratios typical of the orbiting intact objects, these corridors can be exploited only in combination with the action exerted by the atmospheric drag. For satellites equipped with an area augmentation device, we show the boundary of application of the drag, and where the Solar radiation pressure can be exploited.  相似文献   

Statistical identification of orographic effects in the regional analysis of extreme rainfall          下载免费PDF全文

Pierluigi Furcolo  Anna Pelosi  Fabio Rossi 《水文研究》2016,30(9):1342-1353

Regional models of extreme rainfall must address the spatial variability induced by orographic obstacles. However, the proper detection of orographic effects often depends on the availability of a well‐designed rain gauge network. The aim of this study is to investigate a new method for identifying and characterizing the effects of orography on the spatial structure of extreme rainfall at the regional scale, including where rainfall data are lacking or fail to describe rainfall features thoroughly. We analyse the annual maxima of daily rainfall data in the Campania region, an orographically complex region in Southern Italy, and introduce a statistical procedure to identify spatial outliers in a low order statistic (namely the mean). The locations of these outliers are then compared with a pattern of orographic objects that has been a priori identified through the application of an automatic geomorphological procedure. The results show a direct and clear link between a particular set of orographic objects and a local increase in the spatial variability of extreme rainfall. This analysis allowed us to objectively identify areas where orography produces enhanced variability in extreme rainfall. It has direct implications for rain gauge network design criteria and has led to promising developments in the regional analysis of extreme rainfall. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

The geometry of impacts on a synchronous planetary satellite     

G. B. Valsecchi  E. M. Alessi  A. Rossi 《Celestial Mechanics and Dynamical Astronomy》2014,119(3-4):257-270

We consider a satellite in a circular orbit about a planet that, in turn, is in a circular orbit about the Sun; we further assume that the plane of the planetocentric orbit of the satellite is the same as that of the heliocentric orbit of the planet. The pair planet–satellite is encountered by a population of small bodies on planet-crossing, inclined orbits. With this setup, and using the extension of Öpik’s theory by Valsecchi et al. (Astron Astrophys 408:1179–1196, 2003), we analytically compute the velocity, the elongation from the apex and the impact point coordinates of the bodies impacting the satellite, as simple functions of the heliocentric orbital elements of the impactor and of the longitude of the satellite at impact. The relationships so derived are of interest for satellites in synchronous rotation, since they can shed light on the degree of apex–antapex cratering asymmetry that some of these satellites show. We test these relationships on two different subsets of the known population of Near Earth Asteroids.  相似文献   

Oxygen-Rich Cool Stars in the Cepheus Region. New Observations. III     

G. V. Petrosyan  C. Rossi  S. Gaudenzi  R. Nesci 《Astrophysics》2015,58(4):503-511

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Transverse vibrations of a rectangular cantilever plate with thickness varying in a discontinuous fashion     

R.E. Rossi  P.M. Belles  P.A.A. Laura  S. La Malfa  L. Ercoli  D. Pasqua 《Ocean Engineering》1996,23(3):271-276

A numerical solution is obtained for the title problem by means of the popular finite element method. An experimental investigation of the problem is also presented for plates of square planform. The agreement between theoretical and experimental values is very good in the case of the fundamental frequency, and reasonably good when the second and third normal modes of transverse vibration are considered. It is concluded that beneficial effects are obtained in the sense that one generates a lighter structural element with higher fundamental frequency of transverse vibration. Hence, dynamic stiffening is achieved.  相似文献   

Implementing landslide path dependency in landslide susceptibility modelling     

Jalal Samia  Arnaud Temme  Arnold K. Bregt  Jakob Wallinga  John Stuiver  Fausto Guzzetti  Francesca Ardizzone  Mauro Rossi 《Landslides》2018,15(11):2129-2144

Landslide susceptibility modelling—a crucial step towards the assessment of landslide hazard and risk—has hitherto not included the local, transient effects of previous landslides on susceptibility. In this contribution, we implement such transient effects, which we term “landslide path dependency”, for the first time. Two landslide path dependency variables are used to characterise transient effects: a variable reflecting how likely it is that an earlier landslide will have a follow-up landslide and a variable reflecting the decay of transient effects over time. These two landslide path dependency variables are considered in addition to a large set of conditioning attributes conventionally used in landslide susceptibility. Three logistic regression models were trained and tested fitted to landslide occurrence data from a multi-temporal landslide inventory: (1) a model with only conventional variables, (2) a model with conventional plus landslide path dependency variables, and (3) a model with only landslide path dependency variables. We compare the model performances, differences in the number, coefficient and significance of the selected variables, and the differences in the resulting susceptibility maps. Although the landslide path dependency variables are highly significant and have impacts on the importance of other variables, the performance of the models and the susceptibility maps do not substantially differ between conventional and conventional plus path dependent models. The path dependent landslide susceptibility model, with only two explanatory variables, has lower model performance, and differently patterned susceptibility map than the two other models. A simple landslide susceptibility model using only DEM-derived variables and landslide path dependency variables performs better than the path dependent landslide susceptibility model, and almost as well as the model with conventional plus landslide path dependency variables—while avoiding the need for hard-to-measure variables such as land use or lithology. Although the predictive power of landslide path dependency variables is lower than those of the most important conventional variables, our findings provide a clear incentive to further explore landslide path dependency effects and their potential role in landslide susceptibility modelling.  相似文献