Seasonal changes in runoff generation in a small forested mountain catchment   总被引：1，自引：0，他引：1       下载免费PDF全文

D. Penna  H. J. van Meerveld  O. Oliviero  G. Zuecco  R. S. Assendelft  G. Dalla Fontana  M. Borga 《水文研究》2015,29(8):2027-2042

This study aimed to investigate the seasonal variability of runoff generation processes, the sources of stream water, and the controls on the contribution of event water to streamflow for a small forested catchment in the Italian pre‐Alps. Hydrometric, isotopic, and electrical conductivity data collected between August 2012 and August 2013 revealed a marked seasonal variability in runoff responses. Noticeable differences in runoff coefficients and hydrological dynamics between summer and fall/spring rainfall events were related to antecedent moisture conditions and event size. Two‐component and three‐component hydrograph separation and end‐member mixing analysis showed an increase in event water contributions to streamflow with event size and average rainfall intensity. Event water fractions were larger during dry conditions in the summer, suggesting that stormflow generation in the summer consisted predominantly of direct channel precipitation and some saturated overland flow from the riparian zone. On the contrary, groundwater and hillslope soil water contributions dominated the streamflow response during wet conditions in fall. Seasonal differences were also noted between event water fractions computed based on isotopic and electrical conductivity data, likely because of the dilution effect during the wetter months. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

The topographic signature of a major typhoon          下载免费PDF全文

Chih‐Ming Tseng  Ching‐Weei Lin  Giancarlo Dalla Fontana  Paolo Tarolli 《地球表面变化过程与地形》2015,40(8):1129-1136

In August 2009, the typhoon Morakot, characterized by a cumulative rainfall up to 2884 mm in about three days, triggered thousands of landslides in Taiwan. The availability of LiDAR surveys before (2005) and after (2010) this event offers a unique opportunity to investigate the topographic signatures of a major typhoon. The analysis considers the comparison of slope–area relationships derived by LiDAR digital terrain models (DTMs). This approach has been successfully used to distinguish hillslope from channelized processes, as a basis to develop landscape evolution models and theories, and understand the linkages between landscape morphology and tectonics, climate, and geology. We considered six catchments affected by a different degree of erosion: three affected by shallow and deep‐seated landslides, and three not affected by erosion. For each of these catchments, 2 m DTMs were derived from LiDAR data. The scaling regimes of local slope versus drainage area suggested that for the catchments affected by landslides: (i) the hillslope‐to‐valley transitions morphology, for a given value of drainage area, is shifted towards higher value of slopes, thus indicating a likely migration of the channelized processes and erosion toward the catchment boundary (the catchment head becomes steeper because of erosion); (ii) the topographic gradient along valley profiles tends to decrease progressively (the valley profile becomes gentler because of sediment deposition after the typhoon). The catchments without any landslides present a statistically indistinguishable slope–area scaling regime. These results are interesting since for the first time, using multi‐temporal high‐resolution topography derived by LiDAR, we demonstrated that a single climate event is able to cause significant major geomorphic changes on the landscape, detectable using slope–area scaling analysis. This provides new insights about landscape evolution under major climate forcing. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Bank erosion in agricultural drainage networks: new challenges from structure‐from‐motion photogrammetry for post‐event analysis          下载免费PDF全文

Massimo Prosdocimi  Simone Calligaro  Giulia Sofia  Giancarlo Dalla Fontana  Paolo Tarolli 《地球表面变化过程与地形》2015,40(14):1891-1906

Drainage channels are an integral part of agricultural landscapes, and their impact on catchment hydrology is strongly recognized. In cultivated and urbanized floodplains, channels have always played a key role in flood protection, land reclamation, and irrigation. Bank erosion is a critical issue in channels. Neglecting this process, especially during flood events, can result in underestimation of the risk in flood‐prone areas. The main aim of this work is to consider a low‐cost methodology for the analysis of bank erosion in agricultural drainage networks, and in particular for the estimation of the volumes of eroded and deposited material. A case study located in the Veneto floodplain was selected. The research is based on high‐resolution topographic data obtained by an emerging low‐cost photogrammetric method (structure‐from‐motion or SfM), and results are compared to terrestrial laser scanning (TLS) data. For the SfM analysis, extensive photosets were obtained using two standalone reflex digital cameras and an iPhone5® built‐in camera. Three digital elevation models (DEMs) were extracted at the resolution of 0.1 m using SfM and were compared with the ones derived by TLS. Using the different DEMs, the eroded areas were then identified using a feature extraction technique based on the topographic parameter Roughness Index (RI). DEMs derived from SfM were effective for both detecting erosion areas and estimating quantitatively the deposition and erosion volumes. Our results underlined how smartphones with high‐resolution built‐in cameras can be competitive instruments for obtaining suitable data for topography analysis and Earth surface monitoring. This methodology could be potentially very useful for farmers and/or technicians for post‐event field surveys to support flood risk management. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Experimental and numerical evaluation of the fundamental period of undamaged and damaged RC framed buildings   总被引：1，自引：1，他引：0  

Angelo Masi  Marco Vona 《Bulletin of Earthquake Engineering》2010,8(3):643-656

This paper deals with the period evaluation of Reinforced Concrete (RC) framed buildings in elastic, yield and severely damaged states. Firstly, period-height relationships either reported in the literature, or obtained from both numerical simulations (eigenvalue analyses) and experimental measurements (ambient vibration analyses) have been examined and compared. Structural types representing low-rise, mid-rise and high-rise RC buildings without earthquake resistant design, widely present in the Italian and European built environment, have been studied. Results have shown high differences between numerical and experimental period values. Period elongation (stiffness degradation) during and after strong ground shaking has been also examined based on results from experimental in situ and laboratory tests performed on some RC framed building structures which suffered moderate-heavy damage. Some comments on the relationship between damage level and period elongation are reported.  相似文献   

Holocene relative sea-level changes and vertical movements along the Italian and Istrian coastlines   总被引：2，自引：0，他引：2  

F. Antonioli  L. Ferranti  A. Fontana  A. Amorosi  A. Bondesan  C. Braitenberg  A. Dutton  G. Fontolan  S. Furlani  K. Lambeck  G. Mastronuzzi  C. Monaco  G. Spada  P. Stocchi 《Quaternary International》2009,206(1-2):102

Published and new data exist for relative sea-level change for 105 locations (127 samples) during the late Holocene, along the Italian (and Istrian) coasts. These data, compared with predictions (derived from two different models associated with the last glacial cycle) allowed the calculation of the tectonic vertical movements. They are based on precise measures of geomorphological and archaeological markers between 0.4 and 12.6 ka cal. BP, sampled at elevations between +7 and −51 m. In order to decipher the broad pattern of Holocene tectonic vertical movements along the Italian coastline, these data were compared with predicted sea-level curves using the most recent models published for the Mediterranean sea. Tectonic rates varied from −4.85 mm/a, in a core at Sybaris, to 5 mm/a, in the volcanic areas of Pozzuoli and Pantelleria. New MIS 5.5 (125 ka) data, mostly from the Venetian plain, are reported. In particular the depth of the base of MIS 5.5 paralic deposits found in four cores near Venezia provides a mean subsidence of 0.62 mm/a. New, precise mass spectrometer U-Th analyses on Cladocora layers from the bottom of a long core (named ENEA), indicate older ages (195.7 ± 1.6 and 161.2 ± 1.2 ka, respectively), relative to the published MIS 5.5 ages, which were based on alpha-counting U-Th data.Instrumental data obtained from tide gauges and repeated levelling measurements from the NE Adriatic and Sicily are also considered. These methods have one great advantage with respect to continuous GPS measurements and the satellite altimetric observations, in that a much greater time span is available. Although the altimetric measurements are available for 16 years, and the GPS for less than a decade, repeated levelling lines cover up to 50 years and tide gauge observations in some cases to 100 years or more. The greater time span allows for more stable differential rate estimates. The repeated levelling shows that the plain east of Mestre is subsiding (to −4 mm/a). The Messina tidal gauge demonstrates a total coseismic and post-seismic subsidence of 77 cm associated with the event of 1908, the post-seismic phase lasting for at least 13 years. The Reggio Calabria tidal station points to an uplift of this station relative to Palermo in the order of 1–2 mm/a.  相似文献   

Evolution and depositional environments of the Eberswalde fan delta, Mars   总被引：2，自引：0，他引：2  

Monica Pondrelli  Angelo Pio Rossi 《Icarus》2008,197(2):429-451

The Eberswalde crater and its contributing basins have been analyzed in detail in order to reconstruct the geological evolution of the water-related landforms with particular focus on the Eberswalde delta-like feature. Based on a complex strata organization characterized by a topset-foreset-bottomset geometry, typical of delta progradation on Earth, we interpret the Eberswalde feature to be a fan delta associated with a lacustrine system. Depositional sub-environments have been recognized and mapped and the sedimentary processes discussed. A sequence stratigraphy approach has been used to evaluate the system, which we interpret to result from three depositional sequences. These sequences suggest relative water level fluctuations and a longer trend over time towards decreasing water content inside the basin.  相似文献   

Steady flows driven by sources of random strength in heterogeneous aquifers with application to partially penetrating wells     

Gerardo Severino  Alessandro Santini  Angelo Sommella 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):567-582

Average steady source flow in heterogeneous porous formations is modelled by regarding the hydraulic conductivity K(x) as a stationary random space function (RSF). As a consequence, the flow variables become RSFs as well, and we are interested into calculating their moments. This problem has been intensively studied in the case of a Neumann type boundary condition at the source. However, there are many applications (such as well-type flows) for which the required boundary condition is that of Dirichlet. In order to fulfill such a requirement the strength of the source must be proportional to K(x), and therefore the source itself results a RSF. To solve flows driven by sources whose strength is spatially variable, we have used a perturbation procedure similar to that developed by Indelman and Abramovich (Water Resour Res 30:3385–3393, 1994) to analyze flows generated by sources of deterministic strength. Due to the linearity of the mathematical problem, we have focused on the explicit derivation of the mean head distribution G _d (x) generated by a unit pulse. Such a distribution represents the fundamental solution to the average flow equations, and it is termed as mean Green function. The function G _d (x) is derived here at the second order of approximation in the variance σ² of the fluctuation (where K _A is the mean value of K(x)), for arbitrary correlation function ρ(x), and any dimensionality d of the flow domain. We represent G _d (x) as product between the homogeneous Green function G _d ⁽⁰⁾(x) valid in a domain with constant K _A , and a distortion term Ψ _d (x) = 1 + σ²ψ _d (x) which modifies G _d ⁽⁰⁾(x) to account for the medium heterogeneity. In the case of isotropic formations ψ _d (x) is expressed via one quadrature. This quadrature can be analytically calculated after adopting specific (e.g.. exponential and Gaussian) shape for ρ(x). These general results are subsequently used to investigate flow toward a partially-penetrating well in a semi-infinite domain. Indeed, we construct a σ²-order approximation to the mean as well as variance of the head by replacing the well with a singular segment. It is shown how the well-length combined with the medium heterogeneity affects the head distribution. We have introduced the concept of equivalent conductivity K ^eq(r,z). The main result is the relationship where the characteristic function ψ^(w)(r,z) adjusts the homogeneous conductivity K _A to account for the impact of the heterogeneity. In this way, a procedure can be developed to identify the aquifer hydraulic properties by means of field-scale head measurements. Finally, in the case of a fully penetrating well we have expressed the equivalent conductivity in analytical form, and we have shown that (being the effective conductivity for mean uniform flow), in agreement with the numerical simulations of Firmani et al. (Water Resour Res 42:W03422, 2006).  相似文献   

The Use of Close Range Photogrammetry for Studying Ice Accretion on Aerofoil Sections     

P. Collier  L. Dixon  D. Fontana  D. Payne  & A.W. Pearson 《The Photogrammetric Record》1999,16(94):671-684

This paper describes the use of photogrammetry to measure and quantify ice accretion on an aerofoil section. A series of stereoscopic photographs was taken during the ice accretion on the section in an icing tunnel. From measurements made on these photographs with a Kern (Leica) DSR 14 analytical photogrammetric plotter, a series of three dimensional models of the ice surfaces was constructed. The results of the project are discussed and possible improvements in the methodology are suggested.  相似文献   

Data-driven retrieval of primary plane-wave responses     

Giovanni Angelo Meles  Lele Zhang  Jan Thorbecke  Kees Wapenaar  Evert Slob 《Geophysical Prospecting》2020,68(6):1834-1846

Seismic images provided by reverse time migration can be contaminated by artefacts associated with the migration of multiples. Multiples can corrupt seismic images, producing both false positives, that is by focusing energy at unphysical interfaces, and false negatives, that is by destructively interfering with primaries. Multiple prediction/primary synthesis methods are usually designed to operate on point source gathers and can therefore be computationally demanding when large problems are considered. A computationally attractive scheme that operates on plane-wave datasets is derived by adapting a data-driven point source gathers method, based on convolutions and cross-correlations of the reflection response with itself, to include plane-wave concepts. As a result, the presented algorithm allows fully data-driven synthesis of primary reflections associated with plane-wave source responses. Once primary plane-wave responses are estimated, they are used for multiple-free imaging via plane-wave reverse time migration. Numerical tests of increasing complexity demonstrate the potential of the proposed algorithm to produce multiple-free images from only a small number of plane-wave datasets.  相似文献   

A Bayesian hierarchical approach for spatial analysis of climate model bias in multi-model ensembles     

Maeregu?Woldeyes?ArisidoEmail author  Carlo?Gaetan  Davide?Zanchettin  Angelo?Rubino 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(10):2645-2657

Coupled atmosphere–ocean general circulation models are key tools to investigate climate dynamics and the climatic response to external forcings, to predict climate evolution and to generate future climate projections. Current general circulation models are, however, undisputedly affected by substantial systematic errors in their outputs compared to observations. The assessment of these so-called biases, both individually and collectively, is crucial for the models’ evaluation prior to their predictive use. We present a Bayesian hierarchical model for a unified assessment of spatially referenced climate model biases in a multi-model framework. A key feature of our approach is that the model quantifies an overall common bias that is obtained by synthesizing bias across the different climate models in the ensemble, further determining the contribution of each model to the overall bias. Moreover, we determine model-specific individual bias components by characterizing them as non-stationary spatial fields. The approach is illustrated based on the case of near-surface air temperature bias in the tropical Atlantic and bordering regions from a multi-model ensemble of historical simulations from the fifth phase of the Coupled Model Intercomparison Project. The results demonstrate the improved quantification of the bias and interpretative advantages allowed by the posterior distributions derived from the proposed Bayesian hierarchical framework, whose generality favors its broader application within climate model assessment.  相似文献