A data based mechanistic approach to nonlinear flood routing and adaptive flood level forecasting     

Renata J. Romanowicz  Peter C. Young  Keith J. Beven  Florian Pappenberger 《Advances in water resources》2008

Operational flood forecasting requires accurate forecasts with a suitable lead time, in order to be able to issue appropriate warnings and take appropriate emergency actions. Recent improvements in both flood plain characterization and computational capabilities have made the use of distributed flood inundation models more common. However, problems remain with the application of such models. There are still uncertainties associated with the identifiability of parameters; with the computational burden of calculating distributed estimates of predictive uncertainty; and with the adaptive use of such models for operational, real-time flood inundation forecasting. Moreover, the application of distributed models is complex, costly and requires high degrees of skill. This paper presents an alternative to distributed inundation models for real-time flood forecasting that provides fast and accurate, medium to short-term forecasts. The Data Based Mechanistic (DBM) methodology exploits a State Dependent Parameter (SDP) modelling approach to derive a nonlinear dependence between the water levels measured at gauging stations along the river. The transformation of water levels depends on the relative geometry of the channel cross-sections, without the need to apply rating curve transformations to the discharge. The relationship obtained is used to transform water levels as an input to a linear, on-line, real-time and adaptive stochastic DBM model. The approach provides an estimate of the prediction uncertainties, including allowing for heterescadasticity of the multi-step-ahead forecasting errors. The approach is illustrated using an 80 km reach of the River Severn, in the UK.  相似文献   

Assessment of long‐term Holocene soil erosion rates in Polish loess areas using sedimentary archives from closed depressions          下载免费PDF全文

Renata Kołodyńska‐Gawrysiak  Jean Poesen  Leszek Gawrysiak 《地球表面变化过程与地形》2018,43(5):978-1000

Soil erosion is a particularly important problem in the loess areas of Central Europe. Numerous studies of past and present soil erosion based on colluvial sediments have so far been conducted. The main problem is the fact that colluvia usually do not represent the complete sedimentation record. Closed depressions (CDs) collect all colluvial sediments from their catchment, therefore, constitute sediment stores enabling the calculation of soil erosion rates. Colluvial sediments and fossil soils, infilling four CDs in the Polish loess belt, were OSL and C‐14 dated. Human settlements near the studied CDs were analyzed. Phases of soil erosion and colluviation from the Neolithic (5400–2900 bc ), from the Middle Bronze Age to the Early Iron Age (1600–0 bc ), and from the Early Middle Ages to Modern Times (500 AD until today) were documented within the CDs studied. Phases of low soil erosion rate and pedogenesis occurred from the Late Vistulian to the Early Neolithic and from the Iron Age to Early Middle Ages. This study reveals that these phases are not synchronous with the soil erosion phases in Central Europe, as the latter mainly occurred in the Bronze Age, Roman Period and Middle Ages. The obtained soil erosion rates were compared with erosion rates in different areas of Central Europe. This study indicates that in loess regions with long‐term agricultural land use, mean erosion rates (i.e. 3.7–5.9 t ha^‐1 yr^‐1) from the Middle Ages to Modern Times were ten times higher than during the entire prehistoric period (0.39–0.67 t ha^‐1 yr^‐1). The mean soil erosion rates for forested CDs was 0.24–0.74 t ha^‐1 yr^‐1. Soil erosion phases are most probably caused by human activities (i.e. land use change) but the early Holocene erosion phase (7.96 +/‐ 0.67 kyr) could have been induced by a climatic fluctuation (e.g. a 8.2 kyr Bond event). Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Linking 1D coastal ocean modelling to environmental management: an ensemble approach   总被引：1，自引：1，他引：0  

Giulia Mussap  Marco Zavatarelli  Nadia Pinardi 《Ocean Dynamics》2017,67(12):1627-1644

The use of a one-dimensional interdisciplinary numerical model of the coastal ocean as a tool contributing to the formulation of ecosystem-based management (EBM) is explored. The focus is on the definition of an experimental design based on ensemble simulations, integrating variability linked to scenarios (characterised by changes in the system forcing) and to the concurrent variation of selected, and poorly constrained, model parameters. The modelling system used was previously specifically designed for the use in “data-rich” areas, so that horizontal dynamics can be resolved by a diagnostic approach and external inputs can be parameterised by nudging schemes properly calibrated. Ensembles determined by changes in the simulated environmental (physical and biogeochemical) dynamics, under joint forcing and parameterisation variations, highlight the uncertainties associated to the application of specific scenarios that are relevant to EBM, providing an assessment of the reliability of the predicted changes. The work has been carried out by implementing the coupled modelling system BFM-POM1D in an area of Gulf of Trieste (northern Adriatic Sea), considered homogeneous from the point of view of hydrological properties, and forcing it by changing climatic (warming) and anthropogenic (reduction of the land-based nutrient input) pressure. Model parameters affected by considerable uncertainties (due to the lack of relevant observations) were varied jointly with the scenarios of change. The resulting large set of ensemble simulations provided a general estimation of the model uncertainties related to the joint variation of pressures and model parameters. The information of the model result variability aimed at conveying efficiently and comprehensibly the information on the uncertainties/reliability of the model results to non-technical EBM planners and stakeholders, in order to have the model-based information effectively contributing to EBM.  相似文献   

Sedimentary processes in the Stromboli Canyon and Marsili Basin, SE Tyrrhenian Sea: results from side-scan sonar surveys     

R. B. Kidd  R. G. Lucchi  M. Gee  J. M. Woodside 《Geo-Marine Letters》1998,18(2):146-154

 Sedimentary processes in the Stromboli Canyon and in the Marsili Basin are studied on the basis of side-scan sonographs. The basin margins are characterized by slump scars, gullies, channels, and large debrites on the Calabrian slope and by straight chutes of fast downslope sediment transport and blocky–hummocky avalanche deposits on the flanks of the Stromboli volcano. In the Stromboli Canyon and in minor deep-sea channels, sediment transport by turbidity currents generates sediment waves. Between the basin margins and the abyssal plain, the outcropping volcanic basement traps part of the sediment coming from the marginal areas. The abyssal plain is characterized by low relief lobes and ponded sediments.  相似文献   

Persistence of biological invasion effects: Recovery of macroalgal assemblages after removal of Caulerpa racemosa var. cylindracea     

Luigi Piazzi  Giulia Ceccherelli 《Estuarine, Coastal and Shelf Science》2006,68(3-4):455

The present study evaluated the capability of recovery of Mediterranean macroalgal assemblages on rocky bottom invaded by Caulerpa racemosa. A manipulative experiment was performed to compare the structure of native assemblages that: (a) were invaded by the alga, (b) were invaded, but where the invasive alga was removed, and (c) had never been invaded. Macroalgal assemblages differed significantly between areas invaded by C. racemosa and control areas. Moreover, one year after removal of the invader, the recovery of community was minimal. Overall, recovery consisted of a significant increase in species richness and cover of macroalgae, but cover of each vegetation layer (encrusting, turf and erect) did not vary significantly between cleared and Invaded plots through time. Results showed that the effects of the colonization persist after the removal of the alga and the process of recovery of the assemblages appears to be quite slow. This finding might be an important contribution to evaluate invasion costs and thus potentially useful for an effective addressing of control strategies.  相似文献   

Effect of Hydrocarbons and Decontaminating Substances on Bacterial Flora of Coastal Sediments     

Ermanno Crisafi  Renata Zaccone  Lucrezia Genovese  Rosabruna La Ferla  Teresa Luciana Maugeri 《Marine Ecology》1989,10(4):365-375

Abstract. Seventy six samples of coastal sediments collected in the Straits of Messina were studied in order to evaluate the effects of an oil spill and the consequent "clean-up" operations on heterotrophic acrobic bacteria.
In addition, in vitro tests were carried out to estimate the effects of five dispersants on the growth and oil degrading capacity of marine strains isolated from the same sediments.  相似文献   

Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL,CL and RBS/C techniques     

Iwona Jozwik  Jacek Jagielski  Grzegorz Gawlik  Przemyslaw Jozwik  Renata Ratajczak  Gerard Panczer  Nathalie Moncoffre  Anna Wajler  Agata Sidorowicz  Lionel Thomé 《Physics and Chemistry of Minerals》2016,43(6):439-445

A comparative study of damage accumulation in magnesium aluminate spinel (MgAl₂O₄) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl₂O₄ single crystal and polycrystalline samples were irradiated with 320 keV Ar⁺ ions at fluencies ranging from 1 × 10¹² to 2 × 10¹⁶ cm^?2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 10¹³ cm^?2 and second at about 10¹⁵ cm^?2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.  相似文献   

Age and geotectonic setting of Late Neoproterozoic juvenile mafic gneisses and associated paragneisses from the Ribeira belt (SE Brazil) based on geochemistry and Sm–Nd data — Implications on Gondwana assembly     

Renata da Silva Schmitt  Rudolph Allard Johannes Trouw  Silvia Regina Medeiros  Elton Luiz Dantas   《Gondwana Research》2008,13(4):502-515

Mafic gneisses and associated paragneisses from the Cabo Frio Tectonic Domain in the southeastern part of the Ribeira Belt, along the coast of Rio de Janeiro State in southeast Brazil, were subjected to a geochemical and Sm–Nd isotope study. Four lithotypes are distinguished: aluminous paragneisses (mainly sillimanite–kyanite–garnet–biotite gneiss), calcsilicate lenses, quartzo–feldspathic metasedimentary gneisses and mafic–ultramafic lenses. The whole-rock major and trace, including rare earth element distributions in the mafic–ultramafic intercalations indicate that derivation from subalkaline basalt/gabbro of tholeiitic affinity with E-MORB signature from a non-subduction environment. These mafic rocks have positive ε_Nd(t) and T_DM of 1.1 Ga. The metasedimentary rocks have negative ε_Nd(t) and T_DM of 1.7 Ga. A Sm–Nd whole rock isochron of mafic rocks yielded an age of 604 ± 38 Ma for the crystallization. This matches with the age of some detrital zircon grains from the paragneisses. The depositional basin, named Buzios–Palmital, was active at least until 620 Ma (age of the youngest detrital zircon) and was subsequently deformed and metamorphosed at ca. 525 Ma (age of metamorphic zircons) during the Buzios Orogeny. It is interpreted as a back arc basin with relation to the 630 Ma magmatic arc of the Oriental Terrane in the Ribeira Belt to the NW. However, after 600 Ma, the Buzios–Palmital basin changed to an active margin setting because the arc collided with the continental margin and the subduction shifted to the back arc environment. By 610 Ma, most of the Brasiliano belts registered collisional events related to multiple convergent blocks. The stress fields and paleocontinent shapes would have allowed the occurrence of extensional areas with not only sedimentary deposition but also ocean floor spreading. Its remnants are preserved in this Brazilian coastal region as an ancient suture, reworked intensively during the Mesozoic rifting events. The reconnaissance of Late Neoproterozoic basins in the Brasiliano–Pan-African belts is of major importance to partially unravel the final amalgamation events of SW Gondwana. Considering that the Buzios–Palmital basin rock units are mostly covered by the marginal Atlantic basins, it is possible that other evidence could be preserved in the coastal regions of SW-Africa and SE-South America.  相似文献   

Epiphyte assemblages of the Mediterranean seagrass Posidonia oceanica: an overview          下载免费PDF全文

Luigi Piazzi  David Balata  Giulia Ceccherelli 《Marine Ecology》2016,37(1):3-41

This paper reviews the main studies dealing with epiphytes of both leaves and rhizomes of Posidonia oceanica, the main seagrass found in the Mediterranean Sea. A total of 660 epiphyte species has been recorded, including 430 on leaves and 437 on rhizomes. Of these, 205 are Rhodophyta, 59 Ochrophyta, 43 Chlorophyta, 78 Porifera, 82 Cnidaria, 19 Annelida, 155 Bryozoa and 19 Tunicata. The epiphyte assemblages demonstrate a gradient of dissimilarity from west to east, with the eastern area being the most unlike the others. The differences can be attributed mostly to rare species that differ amongst the Mediterranean regions. Many of the dominant taxa have been found in all meadows studied. Data concerning species composition, abundance, and patterns of spatial and temporal variability are summarized, and biotic and abiotic factors controlling the structure of assemblages are discussed. Responses of epiphyte assemblages to anthropogenic stressors, such as nutrient enrichment and biological invasions, are discussed in relation to the use of epiphytes as ecological indicators.  相似文献   

The role of floating mucilage in the invasive spread of the benthic microalga Chrysophaeum taylorii          下载免费PDF全文

Sarah Caronni  Maria Anna Delaria  Kirsten Heimann  Giovanni Macri  Augusto Navone  Pieraugusto Panzalis  Giulia Ceccherelli 《Marine Ecology》2016,37(4):867-876

Chrysophaeum taylorii Lewis & Bryan (Pelagophyceae) is a mucilage‐producing benthic microalga that has recently begun to spread in the Mediterranean Sea, where a range expansion is occurring. This paper presents the results of three field experiments that aimed to increase the knowledge on mucilage provision mechanisms for this benthic microalga and to evaluate the importance of mucilage in its range expansion. By means of two correlative field experiments (several years of data were considered to encompass the variability of mucilage cover) we found that, on the sea bottom, mucilage cover does not depend on epilithic cell density and that both its cover and settling are affected by water flow. We also tested the hypothesis that cells embedded in floating mucilage fall on the underlying substratum, where their abundance depends on water flow. To this aim, in the field we manipulated the presence of floating mucilaginous aggregates in cages with different levels of exposure to winds. The abundance of C. taylorii cells on the substratum under cages with mucilage was compared with that of two control treatments: cages without mucilage and mucilage in still water, in the field and lab, respectively. The results suggested that mucilage can represent an excellent strategy for the species to disperse, as C. taylorii cells fall from the floating mucilage and, if the water flow is unimportant, settle on hard substrata just underneath the cage. This study enriches the portfolio of knowledge of the dispersal strategies of microalgae and contributes to the understanding of the spread of invasive species.  相似文献