Free advanced modeling and remote-sensing techniques for wetland watershed delineation and monitoring

Watershed scale studies focusing on hydrological pressures influencing freshwater ecosystem dynamics are necessary for the establishment of suitable wetland ecological indicators. Enhanced and reproducible methods for watershed modeling and land-cover assessment are thus essential tools for wetland monitoring and management. However, few integrated studies propose advanced open source methodologies for watershed modeling and assessment. In this study, a set of GIS methodological tools was applied and further developed in order to delineate wetland watersheds and map their land-cover changes over time. Watersheds draining to 11 semiarid Mediterranean saline wetlands were delimited and map algebra operations were applied on the digital elevation model in the Campo de Cartagena coastal plain to enhance watershed delimitation. land-use/land-cover maps of wetland watersheds were obtained for years 1987 and 2008 by means of supervised classification of Landsat images. A set of four spectral indices was included in the classification analysis using a combination of bands in order to improve the discrimination of vegetation, water bodies, infrastructure, and bare soil. An iterative classification procedure based on maximum likelihood and random selection of training areas was applied. Contextual information based on automatic image segmentation of Landsat scenes was also included as ancillary layers. Watershed areas obtained ranged from 70 to 17,000 ha and delineation was improved in the Campo de Cartagena coastal plain. The proposed image classification methodology showed high accuracies and improved standard classification techniques. The proposed methodology is based on free and open source tools, which makes it broadly applicable.     

Characteristic friction coefficient and scale effects in oscillatory porous flow

This work presents a simple method to evaluate the performance of a porous breakwater when it is impinged with normal incidence by a non-breaking monochromatic wave train. It is based on: 1) a potential flow model for wave interaction with permeable structures and 2) a set of experimental tests on a rectangular porous structure with uniform granular distribution. A characteristic friction diagram is obtained considering wave energy balance in a control volume, minimising the error between the numerical model and the experimental results for the wave transmission coefficient. Results show that, for large breakwater widths, the reflection process reaches a saturation regime before the waves exit the structure at a distance from the seaside between the interval 0.2 < x/L < 0.45. For larger breakwater widths, the reflection coefficient is almost constant (except for “resonant” conditions) and wave transmission decreases exponentially. Under such conditions, the wave propagation through the porous medium depends on the relative diameter D/L and the porosity of the material; the dependence on the relative breakwater width B/L and the ratio diameter wave height D/H is weak. This diagram intends to be useful for preliminary engineering studies of breakwater's efficiency and performance and as an adequate selection criteria of the experimental stone diameter to minimize scale effects in laboratory studies.     

A Ta,Ti–rich oxide mineral assemblage from the Nancy beryl–columbite–phosphate granitic pegmatite,San Luis,Argentina

Mineralogy and Petrology - An assemblage of tantalite-(Mn), tantalian rutile, tapiolite-(Fe), titanowodginite, ferrotitanowodginite, and hydroxycalciomicrolite occurs in the Nancy granitic...     

Long-term resilience, bush encroachment patterns and local knowledge in a Northeast African savanna

Bush encroachment is a significant phenomenon in savanna environments as it affects wildlife and local livelihoods by preventing new pasture generation. In this article we present a 2000-year record of vegetation change in the Dara range of the Mago National Park, southwestern Ethiopia, an area inhabited by Mursi agro-pastoralists. We use an interdisciplinary approach to understand whether bush encroachment in this area is a recent event or a transitional state of the savanna and describe the local understanding of encroachment as a species-specific process. The vegetation record was obtained from a fossil hyrax midden, a type of sediment already used in Southern Africa but never before in East Africa. Six encroaching phases, led by Capparaceae and Grewia, were found over the last two millennia. The system proved to be resilient, with alternating open and encroached phases, and showed a non-linear response to environmental change, thereby fitting the control theory hypothesis for hysteresis loops. Determining the thresholds conditioning the system's resilience could help to improve savanna management for both local people and National Park authorities.     

Hurricane flood risk assessment for the Yucatan and Campeche State coastal area

Natural Hazards - In this study, the first ever Sea, Lake, Overland Surges from Hurricanes (SLOSH) grid was built for the Yucatan Peninsula. The SLOSH model was used to simulate storm surges in the...     

Petrological,geochemical, isotopic,and geochronological constraints for the Late Devonian–Early Carboniferous magmatism in SW Gondwana (27–32°LS): an example of geodynamic switching

International Journal of Earth Sciences - We report a study integrating 13 new U–Pb LA-MC-ICP-MS zircon ages and Hf-isotope data from dated magmatic zircons together with complete...     

A Subtidal Model of Temperature for a Well-Mixed Narrow Estuary: the Guadalquivir River Estuary (SW Spain)

This paper analyzes thermal energy transport in the narrow and tidally energetic Guadalquivir River Estuary (SW Spain). Measurements from a comprehensive monitoring campaign (2008–2011) reveal the forcing factors of the temperature field and its spatio-temporal variability. The along-channel thermal energy gradient reaches magnitudes of ～375 J/m⁴ near the mouth during the summer and winter. The water temperature is primarily controlled by shortwave radiation, latent heat transfer through the free surface, and tidal advection, whereas it depends less on freshwater discharge and longitudinal dispersion. The tidally averaged effective longitudinal thermal dispersion coefficient was evaluated at several stretches for each tidal cycle. The mean values of the coefficient tend to increase landward and are on the order of ～10³, larger than (but of the same order of magnitude as) the salinity coefficient values. Based on these analyses, a deterministic operational model for thermal energy transport was developed. The model solves the tidally and cross-sectionally averaged advection–dispersion equation for the thermal energy balance and obtains accurate fits of the subtidal temperature field at any location within the estuary. The modeled water temperatures agreed well with the observations at all the stations (coefficients of determination, R ² greater than 0.98), even after the seasonal oscillation in radiation was removed (R ²?>?0.77).     

A Fractal Interaction Model for Winding Paths through Complex Distributions: Application to Soil Drainage Networks

Water interacts with soil through pore channels putting mineral constituents and pollutants into solution. The irregularity of pore boundaries and the heterogeneity of distribution of soil minerals and contaminants are, among others, two factors influencing that interaction and, consequently, the leaching of chemicals and the dispersion of solute throughout the soil. This paper deals with the interaction of irregular winding dragging paths through soil complex distributions. A mathematical modelling of the interplay between multifractal distributions of mineral/pollutants in soil and fractal pore networks is presented. A Hölder path is used as a model of soil pore network and a multifractal measure as a model of soil complex distribution, obtaining a mathematical result which shows that the Hölder exponent of the path and the entropy dimension of the distribution may be used to quantify such interplay. Practical interpretation and potential applications of the above result in the context of soil are discussed. Since estimates of the value of both parameters can be obtained from field and laboratory data, hopefully this mathematical modelling might prove useful in the study of solute dispersion processes in soil.