HYDRAULIC ANALYSES FOR A NEW BRIDGE OVER THE PARANA RIVER, ARGENTINA

1 INTRODUCTION The Parana River in South America ranks as the sixth largest in the world in terms of average discharge (22 x 103 m3/s according to Schumm and Winkley, 1994), and its Argentinean reach stretches from Puerto Iguazu on the north to the Rio de la Plata estuary in the south (Fig. 1). Its estimated average suspended load, bed load, and total load are 23 x 106, 2.2 x 106, and 25.2 x 106 metric tons per year, respectively (Paoli and Schreider, 2001.) The economic developmen…     

Experimental and Numerical Study of the Transport of Acid Solutions and Copper in Tailings Impoundments

A two-dimensional mathematical model for acid leaching of copper from mine tailings using injection and pumping wells is presented. The model considers the transport mechanisms of convection and dispersion with reactions that govern the fates of copper and acid. Reactions considered are acid neutralization, copper solubilization, and copper adsorption. The results of acid leaching experiments in laboratory columns (one- dimensional) and in the field at a tailings impoundment are presented. The proposed model was validated for a one-dimensional experiment, and the model parameter fitting was found to be adequate in terms of the field experiment.     

Integration of geodetic and geotechnical deformation surveys in the geosciences

Ground movement studies can utilize information from conventional geodetic surveying, photogrammetry, and geotechnical measurements of strain, tilt, etc. Each method alone cannot yield a complete picture of the deformation. However, each is complemented by the others. Hence, their integration in a simultaneous analysis in space and in time is advocated. An integrated analysis is readily accommodated by a generalized method of deformation analysis devised by the authors. Any number of measurements of any type can be considered in any fashion of modelling with full statistical assessment of the modelling and of derived characteristics. Such an integration is illustrated using data from a coal mining area in rugged mountainous terrain of western Canada. Conventional terrestrial geodetic methods connected 15 stations. Displacements from an additional 29 points were obtained from aerial photogrammetry. Biaxial tiltmeters continuously measured ground tilts at 3 stations. A surface of subsidence for the whole area was modelled with the graphical depiction in three dimensions.     

The Coherent Pixels Technique (CPT): An Advanced DInSAR Technique for Nonlinear Deformation Monitoring

This paper shows the potential applicability of orbital Synthetic Aperture Radar (SAR) Differential Interferometry (DInSAR) with multiple images for terrain deformation episodes monitoring. This paper is focused on the Coherent Pixels Technique (CPT) developed at the Remote Sensing Laboratory (RSLab) of the Universitat Politecnica de Catalunya (UPC). CPT is able to extract from a stack of differential interferograms the deformation evolution over vast areas during wide spans of time. The former is achieved thanks to the coverage provided by current SAR satellites, like ESA’s ERS or ENVISAT, while the latter due to the large archive of images acquired since 1992. An interferogram is formed by the complex product of two SAR images (one complex conjugate) and its phase contains information relative to topography, terrain deformation and atmospheric conditions among others. The goal of differential interferometric processing is to retrieve and separate the different contributions. The processing scheme is composed of three main steps: firstly, the generation of the best interferogram set among all the available images of the zone under study; secondly, the selection of the pixels with reliable phase within the employed interferograms and, thirdly, their phase analysis to calculate, as the main result, their deformation time series within the observation period. In this paper, the Coherent Pixels Technique (CPT) is presented in detail as well as the result of its application in different scenarios. Results reveal its practical utility for detecting and reproducing deformation episodes, providing a valuable tool to the scientific community for the understanding of considerable geological process and to monitor the impact of underground human activity.     

Hierarchical spatial modeling of the presence of Chagas disease insect vectors in Argentina. A comparative approach

We modeled the spatial distribution of the most important Chagas disease vectors in Argentina, in order to obtain a predictive mapping method for the probability of presence of the vector species. We analyzed both the binary variable of presence-absence of Chagas disease and the vector species richness in Argentina, in combination with climatic and topographical covariates associated to the region of interest. We used several statistical techniques to produce distribution maps of presence–absence for the different insect species as well as species richness, using a hierarchical Bayesian framework within the context of multivariate geostatistical modeling. Our results show that the inclusion of covariates improves the quality of the fitted models, and that there is spatial interaction between neighboring cells/pixels, so mapping methods used in the past, which assumed spatial independence, are not adequate as they provide unreliable results.     

Characterization of wood-laden flows in rivers

Inorganic sediment is not the only solid-fraction component of river flows; flows may also carry significant amounts of large organic material (i.e. large wood), but the characteristics of these wood-laden flows (WLFs) are not well understood yet. With the aim to shed light on these relatively unexamined phenomena, we collected home videos showing natural flows with wood as the main solid component. Analyses of these videos as well as the watersheds and streams where the videos were recorded allowed us to define for the first time WLFs, describe the main characteristics of these flows and broaden the definition of wood transport regimes (adding a new regime called here hypercongested wood transport). According to our results, WLFs may occur repeatedly, in a large range of catchment sizes, generally in steep, highly confined single thread channels in mountain areas. WLFs are typically highly unsteady and the log motion is non-uniform, as described for other inorganic sediment-laden flows (e.g. debris flows). The conceptual integration of wood into our understanding of flow phenomena is illustrated by a novel classification defining the transition from clear water to hypercongested, wood and sediment-laden flows, according to the composition of the mixture (sediment, wood, and water). We define the relevant metrics for the quantification and modelling of WLFs, including an exhaustive discussion of different modelling approaches (i.e. Voellmy, Bingham and Manning) and provide a first attempt to simulate WLFs. We draw attention to WLF phenomena to encourage further field, theoretical, and experimental investigations that may contribute to a better understanding of flows in river basins, leading to more accurate predictions, and better hazard mitigation and management strategies. © 2019 John Wiley & Sons, Ltd.     

Holocene recurrent explosive activity at Chimborazo volcano (Ecuador)

Ice-capped Chimborazo is one of the large composite Ecuadorian volcanoes whose recent eruptive activity is poorly known. This paper presents the characteristics and the ages of a newly discovered Holocene sequence of pyroclastic deposits on the east and north sides of the cone. Lying upon a moraine of the Late-Glacial period, the most complete section of ~ 4.5 m in thickness is located 5 km from the present summit crater. It consists of seven massive or diffusely stratified ash flow layers and four fallout layers interbedded with seven paleosoils.