Comparison of precipitation extremes estimation using parametric and nonparametric methods     

Jan Holešovský  Michal Fusek  Vít Blachut  Jaroslav Michálek 《水文科学杂志》2013,58(13):2376-2386

  相似文献   

Reconstruction of a flash flood with large wood transport and its influence on hazard patterns in an ungauged mountain basin   总被引：2，自引：0，他引：2  

V. Ruiz‐Villanueva  J. M. Bodoque  A. Díez‐Herrero  M. A. Eguibar  E. Pardo‐Igúzquiza 《水文研究》2013,27(24):3424-3437

The reconstruction of past flash floods in ungauged basins leads to a high level of uncertainty, which increases if other processes are involved such as the transport of large wood material. An important flash flood occurred in 1997 in Venero Claro (Central Spain), causing significant economic losses. The wood material clogged bridge sections, raising the water level upstream. The aim of this study was to reconstruct this event, analysing the influence of woody debris transport on the flood hazard pattern. Because the reach in question was affected by backwater effects due to bridge clogging, using only high water mark or palaeostage indicators may overestimate discharges, and so other methods are required to estimate peak flows. Therefore, the peak discharge was estimated (123 ± 18 m³ s^–1) using indirect methods, but one‐dimensional hydraulic simulation was also used to validate these indirect estimates through an iterative process (127 ± 33 m³ s^–1) and reconstruct the bridge obstruction to obtain the blockage ratio during the 1997 event (~48%) and the bridge clogging curves. Rainfall–Runoff modelling with stochastic simulation of different rainfall field configurations also helped to confirm that a peak discharge greater than 150 m³ s^–1 is very unlikely to occur and that the estimated discharge range is consistent with the estimated rainfall amount (233 ± 27 mm). It was observed that the backwater effect due to the obstruction (water level ~7 m) made the 1997 flood (~35‐year return period) equivalent to the 50‐year flood. This allowed the equivalent return period to be defined as the recurrence interval of an event of specified magnitude, which, where large woody debris is present, is equivalent in water depth and extent of flooded area to a more extreme event of greater magnitude. These results highlight the need to include obstruction phenomena in flood hazard analysis. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Seismic activity in the Czech Republic in 2010     

Jan Zedník  Jana Pazdírková 《Studia Geophysica et Geodaetica》2013,57(2):332-337

  相似文献   

A neuro fuzzy approach to recognize rock magnetic and lithological patterns in a stratigraphic well from the Llanos Foreland Basin (Colombia)     

Victoria Camacho  Diego López-Rodríguez  Vincenzo Costanzo-Álvarez  Milagrosa Aldana  Nuri Hurtado  Germán Bayona 《Studia Geophysica et Geodaetica》2013,57(4):669-691

The Neuro Fuzzy System (NFS) is a hybrid algorithm that combines fuzzy logic with neural networks. Since it can be used as a pattern recognition technique, we explore its potential to characterize the major lithological units encompassed by the first 512 m of the Colombian stratigraphic well Saltarin 1A (Guayabo and León Formations). Thus, we employ the NFS to infer the magnetic remanence S-ratio using bulk magnetic susceptibility (κ), κ-normalized saturation isothermal magnetization (SIRM κ) and/or volume of shale (V_sh) obtained from a gamma-ray log. The best results in terms of their corresponding Root Mean-Square Error (RMSE) values, throughout most of the upper Guayabo Formation, where magnetite seems to be an important magnetic phase, are attained with logκ and SIRM κ as input variables. Beyond 350 m downcore, the quality of the inference decreases over the León Formation, characterized by a significant presence of pyrrhotite. However, the extra input variable V_sh adjusts the inferred S-ratio to their experimental counterparts throughout this formation suggesting that the early diagenesis process that led to the formation of dispersed clay in these samples was also responsible for the formation of pyrrhotite. Hence the inclusion of manifold input data increases the ability of the net to predict S-ratio in complex geological settings with a sequence of changing lithologies, varying amounts and types of magnetic minerals, and different distributions of mineral grain sizes. In case these variables do not properly infer the actual S-ratio data, the extent of the different lithostratigraphic units would be still identifiable in some cases by the uneven quality of the correlation observed between inferred and experimental values.  相似文献   

Magnetic particles in atmospheric particulate matter collected at sites with different level of air pollution     

Eduard Petrovský  Radek Zbořil  Tomáš Matys Grygar  Bohumil Kotlík  Jiří Novák  Aleš Kapička  Hana Grison 《Studia Geophysica et Geodaetica》2013,57(4):755-770

Magnetic measurements of deposited atmospehric dust can serve as an additional parameter in assessing environmental pollution. This method is based on the assumption that atmospherically deposited particles contain significant portion of ferrimagnetic iron oxides of anthropogenic origin, which can be easily detected. Aim of this paper is to identify clearly magnetic fraction of daily samples of particulate matter less than 10 μm (PM10), routinely used for air quality assessment and monitoring. We used combination of thermomagnetic analyses and other physical and chemical methods, including scanning electron microscopy (SEM) and Mössbauer spectroscopy. Our results show that daily samples of PM10, collected at sites with different degree of atmospheric pollution, contain magnetite of spherical shape, which is presumably of industrial origin. Thus, magnetic methods can be applied directly to the same substances, which are used routinely in air quality assessment and monitoring.  相似文献   

Petrophysical and geochemical constraints on alteration processes in granites     

Matěj Machek  Zuzana Roxerová  Vojtěch Janoušek  Martin Staněk  Eduard Petrovský  Miloš René 《Studia Geophysica et Geodaetica》2013,57(4):710-740

The hydrothermal alteration of granites has large influence on their petrophysical properties. To reveal the impact of alteration on magnetic and porosity properties of granites we have conducted a complex study of effects of two largely independent alteration processes, related to chemically different fluids, in granites of the Vysoký Kámen stock (the Krudum granite body, Czech Republic). It includes the whole-rock geochemical, magnetic and pore-space characterization. The alkali feldspathization resulted in decomposition of Li-mica, quartz removal, depletion in mafic cations and growth of new alkali feldspars (albite, K-feldspar), decreasing the overall magnetic susceptibility and disrupting the pore space by its discontinuation. The preservation of the orientation of the principal susceptibility axes is likely related to insignificant influence of the feldspathization process on the paramagnetic and diamagnetic phases orientation acquired during the magma emplacement. The greisenization, on the other hand had considerably more significant effects on microstructure and physical properties of the granite. The microstructure was modified by the growth of large amounts of new phases (Li-mica, quartz and topaz). This changed the mineral density of the rock, the porosity, size and character of pores to larger, flatter and probably more connected. This led also to the complete reworking of the original anisotropy of magnetic susceptibility during the greisenization.  相似文献   

Environmental determinants of leech assemblage patterns in lotic and lenitic habitats     

N. Kubová  J. Schenková  M. Horsák 《Limnologica》2013,43(6):516-524

Leeches (Clitellata: Hirudinida) are abundant predators or ecto-parasites inhabiting various freshwater habitats; however many biotic and abiotic drivers of their assemblage patterns have been deduced rather than directly tested. To study species richness and composition changes in leech assemblages, 109 sites of running and stagnant water bodies were sampled in three regions of the Czech Republic in 2007–2010, together with several explanatory variables that are known or expected to be important predictors of leech distribution. In total, 17 species of leeches were recorded, varying between 0–7 and 0–9 species in lotic and lenitic sites, respectively. These differences in species richness of lotic and lenitic sites were highly significant, contrary to the abundances, which varied between 0–283 and 0–295 individuals. The main change in species composition was controlled by water temperature and morphological characteristics (e.g. substrate and cover of macrophytes), mostly reflecting the differences between lotic and lenitic habitats. We found the density of benthos (i.e. prey availability) to be the best predictor of species composition in both lotic and lenitic sites, together with the percentage of canopy cover. However, the other significant predictors (i.e. the substrate and water conductivity found to be significant in lotic sites, and the mean annual temperature and PO₄^3? in lenitic sites), differed between these habitats. Other than mean annual temperature and water temperature, which had different effects on species richness in lotic and lenitic sites, there were no other differences between lotic and lenitic sites in terms of how species richness and abundance responded to all other analyzed predictors. Our results stress the importance of prey availability and canopy for leech distribution patterns. Differences in the significant predictors of leech assemblage patterns between lotic and lenitic sites raise fundamental questions about the underlying mechanisms and ecological constraints to leech distribution in these main types of aquatic systems.  相似文献   

Probabilistic calibration of a distributed hydrological model for flood forecasting     

L. Mediero  L. Garrote  F. J. Martín-Carrasco 《水文科学杂志》2013,58(7):1129-1149

Abstract

The complexity of distributed hydrological models has led to improvements in calibration methodologies in recent years. There are various manual, automatic and hybrid methods of calibration. Most use a single objective function to calculate estimation errors. The use of multi-objective calibration improves results, since different aspects of the hydrograph may be considered simultaneously. However, the uncertainty of estimates from a hydrological model can only be taken into account by using a probabilistic approach. This paper presents a calibration method of probabilistic nature, based on the determination of probability functions that best characterize different parameters of the model. The method was applied to the Real-time Interactive Basin Simulator (RIBS) distributed hydrological model using the Manzanares River basin in Spain as a case study. The proposed method allows us to consider the uncertainty in the model estimates by obtaining the probability distributions of flows in the flood hydrograph.

Citation Mediero, L., Garrote, L. & Martín-Carrasco, F. J. (2011) Probabilistic calibration of a distributed hydrological model for flood forecasting. Hydrol. Sci. J. 56(7), 1129–1149.  相似文献