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51.
This article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at Sparacia experimental area and two ephemeral gullies (EGs) located in the Tremamargi basin, Sicily, Italy. At first, the available literature data together with the measurements carried out in this investigation were used to show that the EG length is a key parameter for the estimation of the eroded volume. Then, the comparison among the pairs length and volume corresponding to measured rills, EGs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type (rill, EG and gully), while a different scale factor has to be used for each erosion process. Finally, a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self‐similarity theory. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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53.
Patuxent landscape model: 1. Hydrological model development 总被引：2，自引：0，他引：2
We developed a spatially explicit, process-based model of the 2352 km2 Patuxent river watershed in Maryland, and its subwatersheds to integrate data and knowledge over several spatial, temporal and complexity scales, and to serve as an aid to regional management. The model was developed using the Library of Hydro-Ecological Modules (LHEM, http://giee.uvm.edu/LHEM), which was designed to create flexible landscape model structures that can be easily modified and extended to suit the requirements of a variety of goals and case studies. The LHEM includes modules that simulate various aspects of ecosystem dynamics. In this paper we consider modules that represent the physical conditions in the environment (climatic factors, geoporphology), and hydrologic processes, both locally and spatially. Where possible the modules are formulated as Stella(R) models, spatial transport processes are presented as C++ code. 相似文献
54.
Costanza Di Stefano Alessio Nicosia Vincenzo Palmeri Vincenzo Pampalone Vito Ferro 《水文研究》2021,35(7):e14296
Recent research recognized that the slope of 18% can be used to distinguish between the ‘gentle slope’ case and that of ‘steep slope’ for the detected differences in hydraulic variables (flow depth, velocity, Reynolds number, Froude number) and those representatives of sediment transport (flow transport capacity, actual sediment load). In this paper, using previous measurements carried out in mobile bed rills and flume experiments characterized by steep slopes (i.e., slope greater than or equal to 18%), a theoretical rill flow resistance equation to estimate the Darcy-Weisbach friction factor is tested. The main aim is to deduce a relationship between the velocity profile parameter Γ, the channel slope, the Reynolds number, the Froude number and the textural classes using a data base characterized by a wide range of hydraulic conditions, plot or flume slope (18%–84%) and textural classes (clay ranging from 3% to 71%). The obtained relationship is also tested using 47 experimental runs carried out in the present investigation with mobile bed rills incised in a 18%—sloping plot with a clay loam soil and literature data. The analysis demonstrated that: (1) the soil texture affects the estimate of the Γ parameter and the theoretical flow resistance law (Equation 25), (2) the proposed Equation (25) fits well the independent measurements of the testing data base, (3) the estimate of the Darcy-Weisbach friction factor is affected by the soil particle detachability and transportability and (4) the Darcy-Weisbach friction factor is linearly related to the rill slope. 相似文献
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Gianluca Bianchini Luigi Beccaluva Costanza Bonadiman Geoff Nowell Graham Pearson Franca Siena Marjorie Wilson 《Lithos》2007,94(1-4):25-45
Mantle xenoliths from the Olot volcanic district (NE Spain) comprise a bi-modal suite consisting of protogranular spinel lherzolites (cpx 12–14%) sometimes with pargasitic amphibole, and highly refractory spinel harzburgites (cpx ≤ 1%) with coarse-grained granular textures. The lherzolites range from slightly depleted to moderately LREE-enriched with flat HREE patterns between 1.5 and 2.7 × chondrite (Ch). In contrast, the harzburgites are extremely depleted in HREE (down to 0.2 × Ch) and strongly LREE-enriched (LaN/YbN = 12.3–17.2). LA-ICP-MS analyses of clinopyroxene and amphibole of the lherzolites highlight variable degrees of LREE depletion (HREE up to 13 × Ch, LaN/YbN down to 0.01), with the exception of a single sample in which both clinopyroxene and amphibole are LREE-enriched (LaN/YbN up to 19). In the harzburgites, clinopyroxenes display totally different REE distributions, characterized by extreme HREE depletion (down to 0.4 × Ch) and upward convex positively fractionated middle-light REE patterns (NdN/YbN up to 20.7 × Ch; LaN/YbN up to 12 × Ch). Sr–Nd–Hf isotopic data for both whole-rocks and cpx separates, coherently indicate depleted mantle (DM) compositions for the lherzolites (εSr = − 15 to − 26, εNd = + 9 to + 17, εHf = + 18 to + 68) and enriched mantle (EM) compositions for the harzburgites (εSr = − 10 to + 36, εNd = − 1 to − 6, εHf = + 3 to + 8). Modelling of the clinopyroxene REE data and isotopic systematics suggest that some lherzolites were affected by pre-Paleozoic (0.6–1 By) low-degree partial melting processes, while others probably reflect some extent of refertilization of the mantle protolith by metasomatizing melts similar to the Triassic rift-related tholeiites reported from several Pyrenean localities. The harzburgites represent extreme refractory residua, resulting from a complex depletion history due to multistage melt extraction as often observed in the cratonic mantle. The distinctive REE patterns and isotopic systematics of their clinopyroxenes suggest that the harzburgites were formed by the interaction of an ultra-depleted peridotite matrix with highly alkaline basic melts similar in composition to the Permo-Triassic alkaline lamprophyres which are widespread within the Iberian plate. Lherzolites possibly represent younger lithosphere (accreted asthenosphere?) up-lifted and juxtaposed to the older subcontinental lithospheric mantle (harzburgites) during the post-Variscan rifting of the Iberian margin. These two genetically different, but adjoining, mantle domains intimately mingled along the northern Iberian margin during the subsequent plate convergence processes, leading to the close association of harzburgites and lherzolites observed in the Olot mantle xenoliths and in some Pyrenean peridotite massifs. 相似文献
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Olaya García Costanza Bonadonna Joan Martí Laura Pioli 《Bulletin of Volcanology》2012,74(9):2037-2050
Quantitative hazard assessments of active volcanoes require an accurate knowledge of the past eruptive activity in terms of eruption dynamics and the stratified products of eruption. Teide–Pico Viejo (TPV) is one of the largest volcanic complexes in Europe, but the associated eruptive history has only been constrained based on very general stratigraphic and geochronological data. In particular, recent studies have shown that explosive activity has been significantly more frequently common than previously thought. Our study contributes to characterization of explosive activity of TPV by describing for the first time the subplinian eruption of El Boquerón (5,660?yBP), a satellite dome located on the northern slope of the Pico Viejo stratovolcano. Stratigraphic data suggest complex shifting from effusive phases with lava flows to highly explosive phase that generated a relatively thick and widespread pumice fallout deposit. This explosive phase is classified as a subplinian eruption of VEI 3 that lasted for about 9–15?h and produced a plume with a height of up to 9?km above sea level (i.e. 7?km above the vent; MER of 6.9–8.2?×?105?kg/s). The tephra deposit (minimum bulk volume of 4–6?×?107?m3) was dispersed to the NE by up to 10?m/s winds. A similar eruption today would significantly impact the economy of Tenerife (e.g. tourism and aviation), with major consequences mainly for the communities around the Icod Valley, and to a minor extent, the Orotava Valley. This vulnerability shows that a better knowledge of the past explosive history of TPV and an accurate estimate of future potentials to generate violent eruptions is required in order to quantify and mitigate the associated volcanic risk. 相似文献
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Marco?PistolesiEmail author Raffaello?Cioni Costanza?Bonadonna Manuela?Elissondo Valerie?Baumann Antonella?Bertagnini Laura?Chiari Rafael?Gonzales Mauro?Rosi Lorella?Francalanci 《Bulletin of Volcanology》2015,77(1):3
After decades of repose, Puyehue-Cordón Caulle Volcano (Chile) erupted in June 2011 following a month of continuously increasing seismic activity. The eruption dispersed a large volume of rhyolitic tephra over a wide area and was characterized by complex dynamics. During the initial climactic phase of the eruption (24–30 h on 4–5 June), 11–14-km-high plumes dispersed most of the erupted tephra eastward towards Argentina, reaching as far as the Atlantic Ocean. This first eruptive phase was followed by activity of lower intensity, leading to the development of a complex stratigraphic sequence, mainly due to rapid shifts in wind direction and eruptive style. The resulting tephra deposits consist of 13 main layers grouped into four units. Each layer was characterized based on its dispersal direction, sedimentological features, and on the main characteristics of the juvenile fraction (texture, density, petrography, chemistry). The lowest part of the eruptive sequence (Unit I), corresponding to the tephra emitted between 4 and 5 June, is composed of alternating lapilli layers with a total estimated volume of ca. 0.75 km3; these layers record the highest intensity phase, during which a bent-over plume dispersed tephra towards the southeast-east, with negligible up-wind sedimentation. Products emitted during 5–6 June (Unit II) signaled an abrupt shift in wind direction towards the north, leading to the deposition of a coarse ash deposit in the northern sector (ca. 0.21 km3 in volume), followed by a resumption of easterly directed winds. A third phase (Unit III) began on 7 June and resulted in tephra deposits in the eastern sector and ballistic bombs around the vent area. A final phase (Unit IV) started after 15 June and was characterized by the emission of fine-grained white tephra from ash-charged plumes during low-level activity and the extrusion of a viscous lava flow. Timing and duration of the first eruptive phases were constrained based on comparison of the dispersal of the main tephra layers with satellite images, showing that most of the tephra was emitted during the first 72 h of the event. The analyzed juvenile material tightly clusters within the rhyolitic field, with negligible chemical variations through the eruptive sequence. Textural observations reveal that changes in eruption intensity (and consequently in magma ascent velocity within the conduit) and complex interactions between gas-rich and gas-depleted magma portions during ascent resulted in vesicular clasts with variable degrees of shear localization, and possibly in the large heterogeneity of the juvenile material. 相似文献
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Francesco G. Carollo Costanza Di Stefano Vito Ferro Vincenzo Pampalone Francesco Sanzone 《地球表面变化过程与地形》2016,41(7):867-874
In order to measure soil loss in equipped plots the estimate of the weight of solid material intercepted at their lower end is required. At the experimental area of Sparacia, Sicily, the runoff produced by an erosive event is collected within storage tanks with a capacity of about 1 m3. In this paper, the use of a new sampler is proposed to measure easily the weight of solid material eroded from an experimental plot and collected into a storage tank. The sampler is a cylinder having a closing valve at the bottom. Two different series of runs were carried out both to test the reliability of the sampler and to establish a sampling procedure, respectively. An analysis of various sampling configurations usable in the field differentiated by the number and location of sampling verticals in the tank cross‐section was finally carried out. The results of the present investigation are that the concentration measurement by the sampler was more accurate than that obtained by other methods involving a collection tank, agitation and sampling of the suspension. This sampler is cheap and usable in combination with a quick field sampling procedure which is particularly advisable when the number of plots equipped at an experimental area is large. The sampler was tested using a clay soil contained within cylinders and a cubic tank, but it appeared also to be usable with coarser sediment than clay and in combination with tanks having a different shape. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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A new numerical–analytical Eulerian procedure is proposed for the solution of convection-dominated problems in the case of existing scalar potential of the flow field. The methodology is based on the conservation inside each computational elements of the 0th and 1st order effective spatial moments of the advected variable. This leads to a set of small ODE systems solved sequentially, one element after the other over all the computational domain, according to a MArching in Space and Time technique. The proposed procedure shows the following advantages: (1) it guarantees the local and global mass balance; (2) it is unconditionally stable with respect to the Courant number, (3) the solution in each cell needs information only from the upstream cells and does not require wider and wider stencils as in most of the recently proposed higher-order methods; (4) it provides a monotone solution. Several 1D and 2D numerical test have been performed and results have been compared with analytical solutions, as well as with results provided by other recent numerical methods. 相似文献