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   

Local Holocene environmental indicators in Upper Mesopotamia: Pedogenic carbonate record vs. archaeobotanical data and archaeoclimatological models     

Simone Riehl  Konstantin E. Pustovoytov  Sara Hotchkiss  Reid A. Bryson   《Quaternary International》2009,209(1-2):154

It has been suggested that pedogenic carbonate coatings on stones in archaeological sites can be used to reconstruct late Quaternary environmental changes in the area of the Fertile Crescent. This research compares a pedogenic carbonate record from southeastern Turkey with three other local or regional sources of palaeoenvironmental information in order to evaluate the correlation of this new proxy with other independent data from the area: (1) ancient plant macroremains from archaeological sites as ecological indicators, (2) stable carbon isotope composition of ancient plant macroremains available in the literature and from our own investigations in six mid-Holocene archaeological sites, and (3) modelled Holocene precipitation and temperature changes in the northern Fertile Crescent. Comparison involved selected palynological and isotopic data from lacustrine sediments as well as speleothem isotopic records in Near Eastern locations available in the literature. Although the data show a certain amount of variation of proxy records on the regional scale, for the northern Fertile Crescent (Upper Mesopotamia) they suggest three pronounced features of the Holocene environmental history: (1) a trend toward warmer temperatures may have affected the area during the early Holocene (between ca. 10,000–6000 cal BP), (2) increased moisture availability and relatively high temperatures in the mid-Holocene (ca. between 5000 and 4000 cal BP), and (3) a significant decrease in moisture availability around 4000 cal BP.Further research is needed to enhance the chronological resolution of both pedogenic carbonate and plant macrofossil records. This study stresses the complexity of the Holocene palaeogeography of the Near East and underlines the need for careful analysis of local sources of palaeonvironmental information in the region.  相似文献   

Intrabasinal conditions promoting the development of a biogenic carbonate sedimentary facies associated with the seagrass Posidonia oceanica     

Giovanni De Falco  Maura Baroli  Andrea Cucco  Simone Simeone 《Continental Shelf Research》2008

This paper aims to elucidate the spatial relationships between the distribution and growth dynamics of Posidonia oceanica, the sedimentary depositional facies (carbonate vs. siliciclastic), and the hydrodynamic features of the Gulf of Oristano (Western Sardinia, Mediterranean sea), a complex depositional system characterized by multiple sources of sediments and a marked hydrodynamic gradient.  相似文献   

An XMM-Newton proton response matrix     

Teresa Mineo  Simone Lotti  Silvano Molendi  Simona Ghizzardi 《Experimental Astronomy》2017,44(3):287-296

Soft protons constitute an important source of background in focusing X-ray telescopes, as Chandra and XMM-Newton experience has shown. The optics in fact transmit them to the focal plane with efficiency similar to the X-ray photon one. This effect is a good opportunity to study the environment of the Earth magnetosphere crossed by the X-ray satellite orbits, provided that we can link the spectra detected by the instruments with the ones impacting on the optics. For X-ray photons this link has the form of the so-called response matrix that includes the optics effective area and the energy redistribution in the detectors. Here we present a first attempt to produce a proton response matrix exploiting ray-tracing and GEANT4 simulations with the final aim to be able to analyse XMM-Newton soft proton data and link them to the external environment. If the procedure is found to be reliable, it can be applied to any future X-ray missions to predict the soft particles spectra impacting on the focal plane instruments.  相似文献   

Organic matter characterisation of the Selli Level (Umbria-Marche Basin, central Italy)     

François Baudin  Nicolas Fiet  Rodolfo Coccioni  Simone Galeotti 《Cretaceous Research》1998,19(6):701-714

The Selli Level is a marker-bed in the Umbria-Marche Apennines that represents the regional sedimentary expression of the Lower Aptain Oceanic Anoxic Event 1a. This one to three-metre-thick interval shows a remarkable uniformity on a regional scale, with a green to grey marly lower part overlain by black shales. Bulk geochemical studies and an examination of palynofacies were carried out on three sections in order to characterise the distribution and nature of the organic matter in the Selli Level which has been poorly known hitherto. The organic content is medium (0.5 to 2.9% TOC) in the basal part and higher (4.5% on average, and up to 18% TOC) in the black shales. Pyrolysis and palynological data indicate that the organic matter is mainly of marine origin. The geochemical characteristics of the Selli Level are compared to other, more or less organic-rich marker-beds in the Cretaceous succession of the Umbria-Marche Apennines.

Abstract

Le Niveau Selli est un niveau-repère des Apennins d'Ombrie-Marches qui correspond à l'enregistrement régional de l'événement anoxique océanique 1a. Ce niveau, épais de un à trois mètres, présente une remarquable uniformité à l'échelle régionale avec une partie inférieure argileuse, verdâtre à grise, surmontée par des black shales. Des analyses géochimiques et l'examen des palynofacies ont été entreprises sur trois coupes afin de caractériser le contenu en matière organique du niveau Selli, jusqu'à présent mal connu. Les teneurs en carbone organique sont moyennes (0,5 à 2,9% COT) dans la partie basale et élevées (4,5% en moyenne et jusque 18% COT) dans les black shales. Les résultats de pyrolyse et des observations palynologiques indiquent que la matière organique est essentiellement d'origine marine. Les caractéristiques géochimiques du niveau Selli sont comparées aux autres niveaux repères, plus ou moins riches en carbone organique, qui émaillent la série du Crétacé du basin d'Ombrie-Marches.  相似文献   

Distribution of diatom assemblages and their relationship to environmental variables in the surface sediments of three northern Egyptian lakes     

Abdelfattah?ZalatEmail author  Simone Servant?Vildary 《Journal of Paleolimnology》2005,34(2):159-174

Surficial sediments of three northern Egyptian lakes (Manzala, Burullus and Edku) show differences in diatom assemblages deposited in different sites of these lakes. A total of 172 species and varieties belonging to 58 genera were identified and counted from 62 samples. Of these, 163 diatom taxa were recorded from Manzala Lake sediments, 147 taxa were found in Burullus Lake sediments, and 117 taxa were identified in Edku Lake sediments. The considerable variation in the composition and distribution of the diatom assemblages among these lakes was mainly related to differences in the water quality, salinity, the concentration of nutrients and climatic changes. The planktonic diatom Cyclotella meneghiniana was dominant in the majority of the samples from Manzala Lake, but dominant in only a few samples from the middle parts of Burullus and Edku lakes. The non-planktonic epiphytic taxa Cocconeis placentula and Epithemia sorex were the subdominant species in the surface sediments, especially in shallow and marginal parts of the lakes. Multivariate statistical techniques (hierarchical ascending clustering and canonical correspondence analysis) were used to identify ecological groups of diatoms and to investigate which environmental variables were important in explaining the variation between these groups. Eight ecological groups containing distinctive diatom assemblages reflect current environmental conditions; especially saltwater intrusion in the north and nutrient-rich freshwater in the south.  相似文献   

Paleolimnological investigations of anthropogenic environmental change in Lake Tanganyika: IV. Lacustrine paleoecology     

Manuel?R.?Palacios-FestEmail author  Simone?R.?Alin  Andrew?S.?Cohen  Brandon?Tanner  Heather?Heuser 《Journal of Paleolimnology》2005,34(1):51-71

Fossil invertebrates from cores collected in Lake Tanganyika provide a record of probable nearshore ecological response to recent watershed deforestation and sediment erosion in several East African watersheds. We compared paleoecological profiles (primarily from ostracodes) from watersheds spanning a range of sizes and present-day deforestation disturbance levels to understand the timing and magnitude of faunal changes, and their relationship in time to terrestrially-derived disturbance indicators. Profiles from the Lubulungu and Nyasanga/Kahama Rivers (Tanzania) provide a record of faunal variability in watersheds that are currently undisturbed with respect to deforestation. These records indicate continuous faunal turnover through time. However, this pattern of turnover is accompanied by relatively high levels of diversity throughout the record, with no wholesale extinction events. Ostracode taphonomic data and other fossil abundance data from the Lubulungu area provide strong evidence in support of at least two episodes of lower lake levels, associated with episodes of Late Holocene aridity. Records from deltas of disturbed watersheds at the Kabesi River (Tanzania) and those of Northern Burundi all show a combination of profound and abrupt faunal turnover, in some cases accompanied by local extinction and establishment of a few dominant taxa. At the Mwamgongo River delta, fed from a very small, disturbed watershed, species turnover was subtler. In disturbed watershed cores showing abrupt faunal changes the transitions mostly occurred in the late 19th to early 20th centuries, predating the major mid-20th century increase in sediment mass accumulation rates, with the latter only correlated with changing fossil abundance and flux. However, the earlier faunal community changes are contemporaneous with both palynological and geochemical changes in the core profiles indicative of changing land-use patterns. This suggests that lacustrine ecosystem response to deforestation was a two-stage process, with an earlier phase of response to changing quality of sediments or dissolved matter being discharged from the watershed, and a subsequent phase responding to increased quantity of sediment.  相似文献   

Acquisition and Inversion of Dispersive Seismic Waves in Shallow Marine Environments   总被引：1，自引：0，他引：1  

Gerald Klein  Thomas Bohlen  Friedrich Theilen  Simone Kugler  Thomas Forbriger 《Marine Geophysical Researches》2005,26(2-4):287-315

Two types of dispersive seismic waves have been acquired in different geological settings to investigate the potential to reveal the elastic parameters of the shallow marine subsurface. Scholte waves as well as acoustic guided waves are excited by a near-surface towed airgun, and recorded using two acquisition methods: (1) the towed-acquisition system using a hydrophone streamer towed close to the sea floor, and (2) the stationary-receiver method using Ocean-Bottom Seismometers and/or Hydrophones (OBS/OBH). Our diverse data sets reveal that the spatial sampling of the wavefield required to avoid aliasing may vary significantly for different geological settings. Scholte waves are characterised by a few distinct modes observed at low frequencies and low phase velocities. Their dispersion is mainly controlled by the depth profile of the shear-wave velocity. Acoustic guided waves show profound amplitude variations of numerous higher modes over a broad frequency range. These are sensitive to shear-wave velocity, but more sensitive to compressional-wave velocity than Scholte waves are. To avoid the identification of distinct modes we infer 1-D models of elastic parameters of the subsurface from the inversion of the full wavefield spectra of acoustic guided waves. In the Siberian Laptev Sea we infer the presence of a soft sediment layer (8–10 m) with a well resolved strong S-velocity gradient (150–450 m/s). In the Baltic Sea a low P-velocity layer with a strong vertical gradient (1250–1440 m/s) corresponding to a post-glacial gassy mud layer could be resolved, which agrees well with the sediment stratigraphy derived from a gravity core.  相似文献   

The impact of commercial and recreational harvesting for Paracentrotus lividus on shallow rocky reef sea urchin communities in North-western Sardinia, Italy     

Antonio Pais  Lorenzo A. Chessa  Simone Serra  Alberto Ruiu  Gianni Meloni  Yuri Donno 《Estuarine, Coastal and Shelf Science》2007,73(3-4):589-597

The fishery for the edible sea urchin Paracentrotus lividus is of great importance to many European regions, although in some of them this species has shown a wide scale decline in recent years. This paper reports on direct (on P. lividus) and indirect (on the co-occurring but not fished echinoid, Arbacia lixula) effects of sea urchin harvesting in shallow rocky reefs in North-western Sardinia (Italy, central-western Mediterranean Sea), where this activity is intensively practised. Density, size (test diameter), and biomass of both species were assessed in autumn 2004 at two locations impacted by P. lividus fishery, and at two controls within an adjacent Marine Protected Area. Density of P. lividus and A. lixula was significantly greater at the controls than at the exploited locations. The average test diameter of P. lividus was also significantly larger at the controls, where large-sized specimens (i.e. >5 cm) were notably more abundant. The average size of A. lixula did not significantly differ between the impacted locations and the controls. The average biomass of P. lividus was significantly greater at the controls than at the exploited locations, whereas no differences were detected for A. lixula. These results reveal the existence of a heavy fishing impact on P. lividus in North-western Sardinia and the need for regulation of its harvesting to prevent severe direct effects on its populations. Since no indirect effects on A. lixula have been detected, it could be hypothesized that this species did not benefit from P. lividus fishery due to an only moderate competition for habitat and resources between these two echinoids. Implications for management of edible sea urchin fishery are also discussed.  相似文献   

Intense drought and flooding events in the Rio Negro and relation with the tropical Pacific and Atlantic variability modes     

Andreoli  Rita Valéria  da Silva  Simone Nazaré Rodriguez  de Souza  Rodrigo Augusto Ferreira  Kayano  Mary Toshie  Garcia  Sâmia Regina  Capistrano  Vinícius Buscioli  Armijos  Elisa 《Theoretical and Applied Climatology》2017,129(1-2):551-576

The relationship of the hydrological variability of the Rio Negro in Manaus and the dominant large-scale climate variability patterns for the 1902–2007 period is investigated using the quantile method and composite analyses. Variations of the Rio Negro Level (RNL) during its 3-month high (May to July—MJJ) and low (October to December—OND) phases are examined separately. The El Niño (La Niña) related maximum warming (cooling) in the central tropical Pacific during its mature and decaying stages modulates the atmospheric circulation in the tropics and displaces the Walker circulation cell eastward (westward), so that its sinking (rising) branch occurs over western Amazon and causes negative (positive) precipitation anomalies in this region. These anomalous climate conditions occur before the Rio Negro high phase (MJJ) and contribute to reduce (increase) the RNL and lead to a very low (very high) event in the river. On the other hand, the SST variability modes in the tropical Atlantic mainly during the transition from wet to dry season modulate the precipitation variations over western Amazon in OND. The very high events are more frequent after the 1960’s decade and the very low events, before the 1930’s decade. Therefore, the occurrence of these events contains a multidecadal scale variability. The results also indicate that the variations in the rainfall in western Amazon occur up to 9 months in advance and modulate the RNL in Manaus. The results presented here might be useful for monitoring purposes of the RNL.

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