The response of drainage basins to the late Quaternary tectonics in the Sicilian side of the Messina Strait (NE Sicily)

Despite more than 40 yr of research attributing temporal changes in streambank erosion rates to subaerial processes, little quantitative information is available on the relationships between streambank erodibility (k_d) and critical shear stress (τ_c) and the environmental conditions and processes that enhance streambank erosion potential. The study goal was to evaluate temporal changes in k_d and τ_c from soil desiccation and freeze–thaw cycling. Soil erodibility and τ_c were measured monthly in situ using a multiangle, submerged jet test device. Soil moisture, temperature, and bulk density as well as precipitation, air temperature, and stream stage were measured continuously to determine changes in soil moisture content and state. Pairwise Mann–Whitney tests indicted k_d was 2.9 and 2.1 times higher (p < 0.0065) during the winter (December–March) than in the spring/fall (April–May, October–November) and the summer (June–September), respectively. Regression analysis showed 80% of the variability in k_d was explained by freeze–thaw cycling alone. Study results also indicated soil bulk density was highly influenced by winter weather conditions (r² = 0.86): bulk density was inversely related to both soil water content and freeze–thaw cycling. Results showed that significant changes in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes. Water resource professionals should consider the implications of increased soil erodibility during the winter in the development of channel erosion models and stream restoration designs.     

Morphologic resilience and depositional processes due to the rapid evolution of the submerged Sciara del Fuoco (Stromboli Island) after the December 2002 submarine slide and tsunami

In order to monitor the Stromboli submarine slope after the 30 December 2002 landslide and tsunami, repeated marine surveys were carried out offshore of Sciara del Fuoco. The morphological changes and depositional processes that brought to the gradual filling of the slide scar have been studied in detail. Thirteen surveys in a period of little more than 4 years provided a unique opportunity to reconstruct the morpho-sedimentary evolution of the submarine slope and its recovery after the mass-wasting event. The scar has been progressively filled with lava and volcanoclastic debris; in the first month and a half, the filling rate was very high due to the entrance of lava flows into the sea and to the morphological readjustment of the slope; in the following months/years the rate dramatically decreased when the eruptive vents moved upwards and the eruption finally stopped. After 4 years (February 2007) more than 40% of the scar was already filled. In early 2007, a new eruption occurred and a lava delta was constructed in the 2002 scar, influencing the natural readjustment of the slope; therefore, our reconstruction only encompasses the period between the 2002 and 2007 eruptions.The swath bathymetry reconstruction of geometry and volume of scar filling during the period 2002–2007 evidenced a punctuated and fast shift of depocenters and debris emplacement through avalanching processes. This process quickly obliterated the features produced by the 2002 tsunamigenic landslide so that a major question about the preservation potential of mass-wasting features on active volcanic flanks emerges.     

The sediment budget and dynamics of a delta‐canyon‐lobe system over the Anthropocene timescale: The Rhone River delta,Lake Geneva (Switzerland/France)

Deltas are important coastal sediment accumulation zones in both marine and lacustrine settings. However, currents derived from tides, waves or rivers can transfer that sediment into distal, deep environments, connecting terrestrial and deep marine depozones. The sediment transfer system of the Rhone River in Lake Geneva is composed of a sublacustrine delta, a deeply incised canyon and a distal lobe, which resembles, at a smaller scale, deep‐sea fan systems fed by high discharge rivers. From the comparison of two bathymetric datasets, collected in 1891 and 2014, a sediment budget was calculated for eastern Lake Geneva, based on which sediment distribution patterns were defined. During the past 125 years, sediment deposition occurred mostly in three high sedimentation rate areas: the proximal delta front, the canyon‐levée system and the distal lobe. Mean sedimentation rates in these areas vary from 0·0246 m year^?1 (distal lobe) to 0·0737 m year^?1 (delta front). Although the delta front–levées–distal lobe complex only comprises 17·0% of the analysed area, it stored 74·9% of the total deposited sediment. Results show that 52·5% of the total sediment stored in this complex was transported toward distal locations through the sublacustrine canyon. Namely, the canyon–levée complex stored 15·9% of the total sediment, while 36·6% was deposited in the distal lobe. The results thus show that in deltaic systems where density currents can occur regularly, a significant proportion of riverine sediment input may be transferred to the canyon‐lobe systems leading to important distal sediment accumulation zones.     

Multivariate Categorical Modeling with Hierarchical Truncated Pluri-Gaussian Simulation

Multiple categorical variables such as mineralization zones, alteration zones, and lithology are often available for geostatistical modeling. Each categorical variable has a number of possible categorical outcomes. The current approach for numerical modeling of categorical variables is to either combine the categorical variables or to model them independently. The collapse of multiple categorical variables into a single variable with all combinations is impractical due to the large number of combinations. In some cases, lumping categorical variables is justified in terms of stationary domains; however, this decision is often due to the limitations of existing techniques. The independent modeling of each categorical variable will fail to reproduce the collocated joint categorical relationships. A methodology for the multivariate modeling of categorical variables utilizing the hierarchical truncated pluri-Gaussian approach is developed and illustrated with the Swiss Jura data set. The multivariate approach allows for improved reproduction of multivariate relationships between categorical variables.

     

Characterization of Risks in Coastal Zones: A Review

Interest in sustainable development for the natural, socio‐economic, and cultural resources of coastal zones is growing worldwide. On the other hand, the range of threats to coastal zones increasingly posed by hydro‐meteorological natural phenomena has led to a trend in the analysis and assessment of risks to these areas. The available literature dealing with coastal risk assessment is quite wide, focusing mainly on the risk evaluation of coastal flooding and erosion resulting directly from the occurrence of extreme natural events. The risk assessment methodologies are usually specific to the conditions and available data of each country, society or location, though most have evolved to assess the risk concept more precisely and rigorously. However, there are still very few studies that present feasible and effective methodologies, which lead to the effective integration of risk analysis at all levels. In Mexico coastal risk analysis has barely begun despite our extensive coastline, which is highly vulnerable to the threat of tropical cyclones. This paper aims to give a broad view of the risk assessment methodologies which already exist, in order to provide a starting point for future efforts in Mexico and elsewhere.     

Hydro‐morphologic Revision of the Cuautla Channel at Nayarit,Mexico

Pollution, habitat modification, and species migration are some of the results of human activities on natural environments which can be mitigated or compensated with proper planning. Irresponsibility or ignorance in planning coastal projects too often produces damage to natural systems which can be unpredictable and sometimes irrevocable. The specific site analyzed in this paper is the Cuautla littoral sub‐system which was originally a lagoon that diverted river water to other lagoons and estuaries, thus irrigating the Mexican Marismas Nacionales system, in the states of Nayarit and Sinaloa, Mexico. In the 1970s social and economic considerations motivated the construction of a small breaching canal from the sea to the lagoon. The subsequent growth of this channel was unforeseen and has produced an irreversible impact not only in the sub‐system but probably in the entire area of Marismas Nacionales. A lack of understanding of the present balances in the damaged system and of the impacts the changing morphology has on future change has created the need to study this area using numerical hydrodynamic simulation. The present distribution of water in the sub‐system was established and the governing processes were detected. By means of an analytical estimation of equilibrium conditions it was found that if nothing is done, the channel will continue eroding and the ecosystem will continue to degrade. Only by understanding the dramatic perturbations caused by the construction of the channel to the hydrologic and morphologic equilibriums can there be any hope of rescuing the ecosystem, including its human activities.     

Molecular and biochemical biomarkers responses in the mussel Mytilus edulis collected from Southern Brazil coast

Marine ecosystems are typically subjected to a variety of stressors containing complex xenobiotics mixtures. This study aims to evaluate the responses of molecular and biochemical biomarkers in the mussel Mytilus edulis providing data for environmental monitoring programs development in Southern Brazil. Mussels were collected at a polluted site, near Patos Lagoon outfall, and at a control site. Gills, muscle and mantle samples were used for biomarker determinations. Mussels collected at the polluted site significantly increased superoxide dismutase (SOD) and glutathione S-transferase (GST) activities and decreased catalase (CAT) activity. Moreover, an increase in sod1, gstπ and hsp70 mRNA expression was observed. Overall, biochemical and molecular biomarkers responses were observed, but these responses varied depending on the analyzed tissue. These results indicate possible contaminants effects on organisms and the need for effective environmental monitoring programs in this ecosystem.     

Magnetic studies and scanning electron microscopy — X-ray energy dispersive spectroscopy analyses of road sediments,soils and vehicle-derived emissions

Human health and environmental problems related to particulate matter emission from vehicles has become a topic of research interest in recent years. These airborne particles can not only be directly inhaled, but are also present as suspended and deposited particles on paved areas and roadside soils. Here we report on magnetic studies, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and chemical analyses of vehicle-derived particles collected from both primary sources and as deposited particles on roads and soils. Preliminary results, recently published by the authors, have revealed that the magnetic signal of such particles is controlled by a magnetite-like phase with magnetic grain size ranging between 0.1 μm and 5 μm. An enrichment of some trace elements: Ba, Cr, Cu, Zn and Pb was also found. In this study we focus on SEM and EDS complementary studies of magnetic extracts. SEM observations showed small individual particles or spherulites, small aggregates in the form of chains or clusters, large aggregates of spherules, flake-like bodies, fibre-like particles, sheet-like particles, irregular debris and large particle agglomerates, i.e. a wide variety of shapes. Grain size distribution is also in agreement with magnetic grain size estimations. Additionally the following elements: C, O, Na, Mg, Al, Si, S, K, Ca, V, Ba, Ti, Cr, Mn, Fe, Cu, Zn and Pb were detected by EDS analysis.     

Geoelectrical investigations in the Cheb Basin/W-Bohemia: An approach to evaluate the near-surface conductivity structure

The Cheb Basin, located in the western Eger (Ohře) Rift, is part of the European Cenozoic Rift system. Although presently non-volcanic, it is the most active area within the European Rift with signs of recent geodynamic activity like emanations of mantle derived CO₂, and the repeated occurrence of swarm earthquakes, which are common features in active volcanic regions. It is assumed that the fluids, uprising in permeable channels, play a key role for the genesis of these earthquake swarms.     

Structural vibration reduction using self-tuning fuzzy control of magnetorheological dampers

Among the control devices considered for dissipating seismic energy and reducing structural vibrations is the magnetorheological (MR) damper which consists of a hydraulic cylinder filled with a suspension of micron-sized, magnetically polarizable iron particles capable of reversibly changing from free-flowing, linear viscous fluid to semi-solid with the application of a magnetic field. Several algorithms have been proposed for regulating the amount of damping provided by MR dampers. An attractive option is the use of fuzzy controllers because they are simple, intrinsically robust, and they do not depend on a model of the system. Tuning of these controllers, however, has shown to be a difficult task because of the large number of parameters involved. This paper proposes a self-tuning fuzzy controller to regulate MR dampers’ properties and reduce structural responses of single degree-of-freedom seismically excited structures. Robustness to changes in seismic motions and structural characteristics was assessed by subjecting a rigid and a flexible building to different earthquake records. Results show that the self-tuning controller proposed effectively reduced responses of both structures to all earthquakes considered. In addition, results were compared to those of a fuzzy controller with constant scaling factors and to those of two passive strategies: “passive on” and “passive off”, where the current to the MR dampers was set to its maximum allowable value, and zero, respectively.