Agricultural risk management policies under climate uncertainty

Climate change is forecasted to increase the variability of weather conditions and the frequency of extreme events. Due to potential adverse impacts on crop yields it will have implications for demand of agricultural risk management instruments and farmers’ adaptation strategies. Evidence on climate change impacts on crop yield variability and estimates of production risk from farm surveys in Australia, Canada and Spain, are used to analyse the policy choice between three different types of insurance (individual, area-yield and weather index) and ex post payments. The results are found to be subject to strong uncertainties and depend on the risk profile of different farmers and locations; the paper provides several insights on how to analyse these complexities. In general, area yield performs best more often across our countries and scenarios, in particular for the baseline and marginal climate change (without increases in extreme events). However, area yield can be very expensive if farmers have limited information on how climate change affects yields (misalignment in expectations), and particularly so under extreme climate change scenarios. In these more challenging cases, ex post payments perform well to increase low incomes when the risk is systemic like in Australia; Weather index performs well to reduce the welfare costs of risks when the correlation between yields and index is increased by the extreme events. The paper also analyses the robustness of different instruments in the face of limited knowledge of the probabilities of different climate change scenarios; highlighting that this added layer of uncertainty could be overcome to provide sound policy advice under uncertainties introduced by climate change. The role of providing information to farmers on impacts of climate change emerges as a crucial result of this paper as indicated by the significantly higher budgetary expenditures occurring across all instruments when farmers’ expectations are misaligned relative to actual impacts of climate change.     

From the plutonic root to the volcanic roof of a continental magmatic arc: a review of the Neoproterozoic Araçuaí orogen,southeastern Brazil

International Journal of Earth Sciences - The Araçuaí-West Congo orogen (AWCO) is one of the various components of the Brasiliano/Pan-African orogenic network generated during the...     

Free rocking response of a regular stone masonry wall with equivalent block approach: experimental and analytical evaluation

The evaluation of the dynamic behaviour of rocking elements is directly correlated to the energy dissipated because of the impacts at the base interface, which can be represented by means of a coefficient of restitution. This schematization is commonly accepted as representative of the out‐of‐plane response of stone masonry walls. An experimental campaign (in a lab environment) aiming at assessing the value of this coefficient for a sacco granite masonry wall is presented in this work. The rocking motion at a predefined bed joint level was induced in the tested specimens in order to validate a novel test setup designed to assess the coefficient of restitution value by means of a realistic reproduction of the rocking behaviour of a single element, under the hypothesis of an infinitely stiff system above the bed joint level. As the main objective of the work was to assess the rocking behaviour of a masonry wall that looses energy at the impacts at a certain joint level, the flexural behaviour was not desirable and had to be avoided. For this purpose, a test setup based on the equivalent block approach was developed. In the final section of this work, comparisons between experimental and numerical results are presented together with some preliminary conclusions on the appropriate modelling strategy and the values of the coefficient of restitution to be used for the seismic assessment of the out‐of‐plane rocking behaviour of this type of sacco stone masonry walls. Copyright © 2013 John Wiley & Sons, Ltd.     

Radiological and geochemical characteristics of an ultramafic massif (NE Portugal) regarding the site aptness to host a near surface repository for low and intermediate level radwaste

The search for suitable sites to install near-surface repositories for low to intermediate level radioactive wastes has increased in the recent years, reflecting both the continuous rise in radioactive materials applications by the society and the increasing awareness of public perception regarding radwaste management. International recommendations towards the application of higher safety standards to low and intermediate level waste disposal sites being developed by the International Atomic Energy Agency (IAEA), and the European Commission decision that each Member State must safely dispose its own radwaste in its territory, according to national radwaste management plans, has leading to new soundly scientific studies. In Portugal, possible locations for that purpose are under study since 2006, following the pre-requisites indicated by IAEA. One of these sites overlaps a significant portion of an ultramafic massif, corresponding to an allochthonous and metamorphosed ophiolite complex. In the surveyed area of this massif, the prevailing rock type consists of (serpentinised) peridotites, occasionally containing irregular bodies of (amphibolitised) gabbros, over which an irregular/ill-developed regolith exists. The activities of ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra and ²³²Th measured in samples representing three consecutive levels of the regolith upper portion in 13 stations confirm the heterogeneity put in evidence through in situ γ-ray surveys previously performed. The available dataset also demonstrates that radionuclide contents decrease prominently with depth, becoming closer to the bedrock values (up to ca. 41 Bq kg^?1 for ⁴⁰K in flaser-gabbros and near zero for all the remaining cases) but never reaching them. Therefore, the low/moderate radionuclide activity in the regolith upper portion reflect the contribution of sources that are independent of the lithological background; i.e. they indicate external and miscellaneous contributions to the “soil”-forming components, most of them coming from (dry or wet) atmospheric deposition. The chemical composition of the (serpentinised) peridotites and (amphibolitised) gabbros in the surveyed area, as well as their alteration products included in regolith, is homogeneous enough to be used as a faithful reference in monitoring studies of any kind. In addition, the significant ¹³⁷Cs activities measured in some top “soil” samples (up to 92 Bq kg^?1) strongly suggest that there are mineralogical specificities of the peridotite-derived regolith able to fix that radionuclide. This particular feature reinforces the existing criteria that favour the peridotites of Morais as a suitable host for a near surface repository of low to intermediate level radwaste.     

Non-destructive microtomography-based imaging and measuring laboratory-induced degradation of travertine, a random heterogeneous geomaterial used in urban heritage

The aim of this study is to apply X-ray microfocus computed microtomography (μ-XCT), a promising non-destructive 3D microscopy imaging technique, based on measurements of X-ray linear path attenuation coefficient, in order to study a Portuguese travertine, a random heterogeneous geomaterial used in urban heritage constructions. This study evaluates the impact of soluble sulphate salt–induced decay phenomena on texture characteristics at a micrometric scale. This is done to better describing, imaging, measuring and understanding the impact of an artificially induced sulphate-decay process on petrographic/petrophysical properties. A Portuguese travertine was chosen as the object of our study. Its laboratory-induced changes were systematically monitored, using non-destructive techniques, to determine voids (pores + fractures)/matrix fractions and size spectrum evolution based on 3-D images. This investigation demonstrates that the μ-XCT potential constitutes a valid complementary tool when analysing decay processes of complex natural materials in different environmental conditions. It clearly provides suggestive and important qualitative and/or quantitative estimates, at different spatial scales, of environmentally induced stone voids/matrix network spatial structure-texture evolution correlations. Further qualitative/quantitative parameterization assessment and statistical validation will be the next step to be taken on this study.     

Data-driven modeling for groundwater exploration in fractured crystalline terrain, northeast Brazil

It is not possible, using numerical methods, to model groundwater flow and transport in the fractured crystalline rock of northeastern Brazil. As an alternative, the usefulness of self-organizing map (SOM), k-means clustering, and Davies-Bouldin techniques to conceptualize the hydrogeology was evaluated. Also estimated was the well yield and groundwater quality across the Juá region. This process relies on relations in the underlying multivariate density function associated with a sparse local set of hydrogeologic (electrical conductivity, geology, temperature, and well yield) and a complete regional set of airborne geophysical (electromagnetic, magnetic, and radiometric) and satellite spectrometric measurements. Resampling of the regional well yield and electrical conductivity estimates provides sufficient resolution to construct variograms for stochastic modeling of the hydrogeologic variables. The combination of these stochastic maps provides a way to identify potential drilling targets for future groundwater development. The data-driven estimation approach, when applied to available airborne electromagnetic and water-well hydrogeologic measurements, provides a low-cost alternative to numerical groundwater flow modeling. In addition to fractured rock environments, the alternative modeling framework can provide spatial parameter estimates and associated variograms for constraints to improve the traditional calibration of equivalent groundwater-porous-media models.     

Seismotectonic versus man-induced morphological changes in a cave on the Arrábida chain (Portugal)

Abstract

Distinctions between cave morphologies originating from seismic or active tectonics and those generated by natural clastic breakdown or by human activity must be made using unambiguous interpretative criteria.

Easily accessible caves in particular, which may have been visited for centuries or millennia, or caves located near engineering works or quarries using great quantities of explosives, may have broken speleothems, breakdowns or detachment joints unrelated to seismic events or tectonic movements.

Zambujal cave lies near neotectonic and seismic structures associated with a Plio-Quatemary 200 m uplift of the Arrábida chain and has suffered impacts resulting from quarrying, followed by possible vandalism. It is thus an example for which it is difficult to decipher morphological agents as there is the possibility that identical forms have been generated by several causes, which may have repeated at different episodes of its evolution. However, a careful morphological interpretation makes it possible to accept the existence of two seismic episodes, an “ancient” one and a “modern” one. The detection of other episodes between these is only possible using absolute dating. © Elsevier, Paris     

Development of an innovative seismic strengthening technique for traditional load-bearing masonry walls

Traditional non-reinforced masonry walls are particularly prone to failure when subjected to out-of-plane loads and displacements caused by earthquakes. Moreover, singularities such as openings in fa?ades may trigger local collapse, for either in-plane or out-of plane motion. Bearing in mind all the former limitations, STAP, with the scientific support of ICIST and LNEC, has been developing a reduced intrusiveness seismic strengthening methodology for traditional masonry structures. The technique consists in externally applying Glass Fibre Reinforced Polymer (GFRP) composite strips to one or both faces of walls. Connection between GFRP composite strips and masonry substrate is enhanced through specifically detailed anchorages or confinement connectors. This technique has been developed and studied through an extensive series of experimental tests, which are briefly reviewed. This paper focuses more deeply on the latest experimental program, aimed at the characterization of the masonry-GFRP composite interface behaviour. This testing program comprised 29 masonry specimens, strengthened with externally bonded GFRP composite strips with anchorages. The testing variables were the number and spacing of anchorages as well as the loading history type: monotonic or repeated. Results clearly show that the use of anchorages dramatically enhances bond behaviour and that its number and spacing have a significant effect on deformation capacity and a less pronounced effect on strength. Based on experimental evidence, this paper also provides a calculation model and ULS safety assessment procedure for out-of-plane strength of reinforced masonry walls. This calculation model leads to interaction curves on strengthened masonry walls subjected to compression and out-of-plane flexure.     

Calibration and application of a continuum damage model on the simulation of stone masonry structures: Gondar church as a case study

The conservation and rehabilitation of monuments is a matter of important investigation, and the need for accurate structural analysis, capable of effectively predicting the structural behaviour of this type of constructions, under static and dynamic loads, is increasing. Currently there are numerous computational methods and tools, supported by different theories and strategies with different levels of complexity, computation time and cost which are available to perform such analyses. A complex analysis is not always synonym of a better result and the choice of a method over another depends mostly on the purpose of the analysis. This work aims at evaluating the capacity of a non linear continuum damage model (Faria et al. in Int J Solids Struct 35(14):1533–1558, 1998), originally developed for concrete structures, to simulate the behaviour of stone masonry structures. In particular, the seismic response of an old stone masonry construction, the Gondar church, is analysed considering different levels of geometrical and material complexity. The verification and calibration procedures use the experimental results from tests performed on stone masonry walls at the Laboratory for Earthquake and Structural Engineering of the Faculty of Engineering of Porto University and from other tests found in the bibliography (Vasconcelos in Experimental investigations on the mechanics of stone masonry: Characterization of granites and behaviour of ancient masonry shear walls. PhD Thesis, Universidade do Minho, Guimar?es, Portugal, 2005). The results are compared, assessing the differences and the importance of using complex tools, such as the continuum damage model, to better simulate and understand the global behaviour of such constructions.