Analysis of sedimentary processes on the Las Canteras beach (Las Palmas, Spain) for its planning and management

The sedimentary dynamics of a sandy beach located on the North coast of the Island of Gran Canaria has been studied in relation to physical processes.

The morphodynamic behaviour of the beach has been established and interpreted. Special emphasis has been placed on the characterization of erosive and accretionary processes by means of sediment transport calculations. Two sedimentary indices have been used to define these processes qualitatively and quantitatively. These indices are of importance for management.     

Runoff modifications due to the conversion of natural grasslands to forests in a large basin in Uruguay

Uruguay has encouraged the development of the forestry sector since 1989. As a member of the Montreal Process, the country has followed a set of criteria and indicators for the Sustainable Forest Management. The aim of this paper is to describe the studies carried out in a large basin of 2097 km², located in an area of humid subtropical climate and 1300 mm of long‐term mean annual rainfall, where the conversion of natural grasslands to forests increased up to 540 km² during the last 15 years. Using data from daily rainfall and streamflow, the study analyses the effects of afforestation on the runoff and water loss. The analysis comprises hydrographs resulting from comparable rainfall events and annual and seasonal streamflow and water loss behaviour, both before afforestation (1975–1993) and during the afforestation period (1994–2008). A statistically significant reduction of runoff volumes (33–43%) and peak flows (59–65%) were identified on storm hydrographs. The annual and seasonal streamflow also showed diminishing tendencies due to the forestry development, whereas the water loss increases. The annual streamflow decreased between 8·2 and 36·5% depending on the annual rainfall totals. The streamflow reduction was higher during spring and summer (25·2–38·4%) and smaller during autumn and winter (15–20·3%). The water loss is expected to increase by 98 mm for the long‐term mean annual rainfall. The resulting information is a valuable input for the Integrated Water Resources Management of the Negro river basin located downstream, where hydroelectric power, rice irrigation and forestry development are supported. Copyright © 2008 John Wiley & Sons, Ltd.     

Trees,soil moisture and foundation movements

Trees growing close to buildings in urban landscapes may change the soil moisture around foundations, producing shrinkage and swelling. This paper presents a numerical solver to estimate the movements resulting from these volumetric strains. This tool will be of assistance in both designing the footings of new buildings and in the analysis of damage associated with buildings that have already been constructed. The conceptual model used is based on current knowledge of the hydro-mechanical behaviour of unsaturated soils. Its numerical implementation is simple, making it easy for users to make changes as they see fit. The program has been verified, validated, and applied in a real stabilization problem.     

Morphology and sedimentary systems in the Central Bransfield Basin, Antarctic Peninsula: sedimentary dynamics from shelf to basin

A detailed regional characterization of the physiography, morphology and sedimentary systems of the Central Bransfield Basin (CBB) was carried out using swath bathymetry and high‐ and very high‐resolution seismic profiles. The basin margins show continental shelves with numerous glacial troughs, and continental slopes where relatively wide and flat slope platforms represent the middle domain in an atypical physiographic scenario in glaciated margins. Although the CBB is tectonically active, most of the morphologic features are sedimentary in origin, and can be classified into four sedimentary systems: (1) glacial‐glaciomarine, composed of erosional surfaces, glacial troughs, furrows and draping sheets; (2) slope‐basin, formed by trough mouth fans, slope aprons, the Gebra‐Magia instability complex and turbidity systems; (3) seabed fluid outflow system composed of pockmark fields; and (4) contourite, composed of drifts and moats. The sedimentary systems show a clear zonation from shelf to basin and their dynamics reflects the complex interplay among glacial, glaciomarine, marine and oceanographic processes involved in the entire shelf‐to‐basin sediment distribution. The CBB morphology is primarily controlled by glacial/interglacial cyclicity and physiography and to a lesser extent by tectonics and oceanography. These factors have affected the South Shetland Islands (SSI) and Antarctic Peninsula (AP) margins differently, creating a relatively starved SSI margin and a more constructional AP margin. They have also created two entire sediment‐dispersal domains: the shelf‐to‐slope, which records the glaciation history of the CBB; and the lower slope‐to‐basin, which records the imprint of local factors. This study provides a ‘source‐to‐sink’ sedimentary scheme for glaciated margins, which may be applied to the basin research in other margins, based on the characterization of sedimentary systems, their boundaries and the linkages among them. This approach proves to be adequate for the identification of global and local factors governing the CBB and may therefore be applied to other study areas.     

Eastern boundary drainage of the North Atlantic subtropical gyre

The eastern boundary of the North Atlantic subtropical gyre (NASG) is an upwelling favorable region characterized by a mean southward flow. The Canary Upwelling Current (CUC) feeds from the interior ocean and flows south along the continental slope off NW Africa, effectively providing the eastern boundary condition for the NASG. We follow a joint approach using slope and deep-ocean data together with process-oriented modeling to investigate the characteristics and seasonal variability of the interior–coastal ocean connection, focusing on how much NASG interior water drains along the continental slope. First, the compiled sets of data show that interior central waters flow permanently between Madeira and the Iberian Peninsula at a rate of 2.5?±?0.6 Sv (1 Sv = 10⁶ m³ s^-1 10⁹ km s^-1), with most of it reaching the slope and shelf regions north of the Canary Islands (1.5?±?0.7?Sv). Most of the water entering the African slope and shelf regions escapes south between the easternmost Canary Islands and the African coast: In 18 out of 22 monthly realizations, the flow was southward (?0.9?±?0.4?Sv) although an intense flow reversal occurred usually around November (1.7?±?0.9?Sv), probably as the result of a late fall intensification of the CUC north of the Canary Islands followed by instability and offshore flow diversion. Secondly, we explore how the eastern boundary drainage may be specified in a process-oriented one-layer quasigeostrophic numerical model. Non-zero normal flow and constant potential vorticity are alternative eastern boundary conditions, consistent with the idea of anticyclonic vorticity induced at the boundary by coastal jets. These boundary conditions cause interior water to exit the domain at the boundary, as if recirculating through the coastal ocean, and induce substantial modifications to the shape of the eastern NASG. The best model estimate for the annual mean eastward flow north of Madeira is 3.9?Sv and at the boundary is 3.3?Sv. The water exiting at the boundary splits with 1?Sv flowing into the Strait of Gibraltar and the remaining 2.3?Sv continuing south along the coastal ocean until the latitude of Cape Ghir. The model also displays significant wind-induced seasonal variability, with a maximum connection between the interior and coastal oceans taking place in autumn and winter, in qualitative agreement with the observations.     

Relating Hyperspectral Airborne Data to Ground Measurements in a Complex and Discontinuous Canopy

The work described in this paper is aimed at validating hyperspectral airborne reflectance data collected during the Regional Experiments For Land-atmosphere EXchanges (REFLEX) campaign. Ground reflectance data measured in a vineyard were compared with airborne reflectance data. A sampling strategy and subsequent ground data processing had to be devised so as to capture a representative spectral sample of this complex crop. A linear model between airborne and ground data was tried and statistically tested. Results reveal a sound correspondence between ground and airborne reflectance data (R2 > 0.97), validating the atmospheric correction of the latter.     

STARE Results on a Single Field: Tens of New Pulsating Stars

We present preliminary results on variable stars of aSTARE's three month observational run centered at the Cygnus constellation.A total amount of aprox. 14000 stars with 9^2 FOV, have been analyzed to obtainlightcurves for each of these stars.The data spans for 90 nights.In this single field, we detect more that 40 stars withpulsation modes between 5 and 40 c/d, the vast mayoritypreviously unknown to be variables.     

Expansive bentonite-sand mixtures in cyclic controlled-suction drying and wetting

Expansive clay buffers in radioactive waste disposal designs experience cyclic drying and wetting paths during different stages of their design life. Clayey soils subjected to these processes develop swelling and shrinkage deformations, which give rise to the accumulation of compression or expansion strains during suction cycles. Experimental studies were undertaken using oedometer tests on an artificially prepared bentonite-sand mixture (80% bentonite by dry mass). In order to study these processes and to identify the most important features controlling soil behaviour, several wetting-drying cycles with suctions ranging between 130 and 4 MPa were applied using vapour equilibrium technique and covering a wide range of overconsolidation ratios (OCR). The tested samples showed cumulative shrinkage strains along the successive cycles, which became more significant at increasing vertical net stresses (low OCR values). However, no accumulation of expansion strains was detected at elevated OCR values. Test results were interpreted and predicted within the context of an elastoplastic model proposed by Alonso et al., 1999, [Alonso, E.E., Vaunat, J., Gens, A., (1999). Modelling the mechanical behaviour of expansive clays. Engineering Geology, 54, 173-183.] which takes into account the accumulation of strains. A good correspondence between measured soil response and model predictions was observed. The paper also presents the methodology to derive the constitutive parameters.     

Preliminary aspects of rainfall rates in the north east of Spain

Summary A series of charts of rainfall rates recorded by means of a Jardí pluviograph in Barcelona, Spain, and covering a period of 20 years have been digitised. The time intervals of exceedance of certain pre-set rainfall rate thresholds were computed and expressed in percentages of the whole 20-year period. The average worst month period and the absolute worst month were defined and computed. Results are found to agree well with those obtained elsewhere in Southern Europe; they are also compared with some published results for Kew. Frequency-distribution of rates as well as time of occurrence are presented. Rainfall amounts pertaining to several rainfall rate categories have been analysed in order to obtain the ratio of convective to total rainfall amount. Comparison of this ratio with results of some other authors is inconclusive.

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Zusammenfassung Eine Anzahl von Tabellen über Niederschlagsraten, die in Barcelona (Spanien) durch einen Jardí Niederschlagsmesser über eine Zeitspanne von 20 Jahren aufgezeichnet wurden, werden bearbeitet. Die Andauer von gewissen festliegenden Niederschlagsraten wurde berechnet und in Prozenten von der gesamten 20jährigen Zeitspanne ausgedrückt. Die durchschnittliche Dauer im schlechtesten Monat, sowie der absolut schlechteste Monat werden definiert und berechnet. Die Ergebnisse stimmen im allgemeinen mit solchen anderer südeuropäischer Gebiete überein; sie werden mit schon veröffentlichten Ergebnissen aus Kew verglichen. Häufigkeits- als auch Verteilungsraten sowie die Eintrittszeit der Ereignisse werden angegeben. Die Niederschlagsmengen, die jeweils zu verschiedenen Niederschlagsraten gehören, wurden analysiert, um das Verhältnis des konvektiven zum gesamten Niederschlag zu ermitteln. Ein Vergleich dieses Verhältnisses mit den Ergebnissen anderer Autoren sind noch nicht abgeschlossen.

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With 7 Figures