Depth of closure: New calculation method based on sediment data

Obtaining depth of closure (DoC) in an accurate manner is a fundamental issue for coastal engineering, since good results for coastal structures and beach nourishment depend mainly on DoC. Currently, there are two methods for obtaining the DoC, mathematical formulations and profile surveys. However, these methods can incur important errors if one does not take into account the characteristics and morphology of the area, or if one does not have a sufficiently long time series. In this work the DoC is obtained from the break in the trend of the sediment with the depth, that is, in general with the increase of the depth a decrease in the size of the sediment takes place. However, at one point this tendency changes and the size increases, and then decreases again. When comparing the point where the minimum sediment size occurs before the increase, it is observed that the error incurred is small compared to other methods. If the Standard Deviation of Depth Change (SDDC) method is considered as the most accurate method, the error incurred by the proposed method is less than 7%. In addition, it can be seen that the dispersion of the sediment method always occurs outside the zone of bar movement. Whereas in the methods of profiles survey (using 2 cm precision profiles), sometimes the DoC is obtained within the active zone of bar movement. In addition, where the relative minimum of the median sediment size is found, and the sizes of 0.063 and 0.125 mm predominate in the composition of the sample. Therefore, this new method allows the precise location of the DoC to be obtained in a fast and simple way. Furthermore, this method has the advantage that it is not affected by the modifications that may be experienced by both the study area and the cross-shore beach profile.     

Real‐time distributed hybrid testing: coupling geographically distributed scientific equipment across the Internet to extend seismic testing capabilities

Large‐scale testing and qualification of structural systems and their components is crucial for the development of earthquake engineering knowledge and practice. However, laboratory capacity is often limited when attempting larger experiments due to the sheer size of the structures involved. To overcome traditional laboratory capacity limitations, we present a new earthquake engineering testing method: real‐time distributed hybrid testing. Extending current approaches, the technique enables geographically distributed scientific equipment including controllers, dynamic actuators and sensors to be coupled across the Internet in real‐time. As a result, hybrid structural emulations consisting of physical and numerical substructures need no longer be limited to a single laboratory. Larger experiments may distribute substructures across laboratories located in different cities whilst maintaining correct dynamic coupling, required to accurately capture physical rate effects. The various aspects of the distributed testing environment have been considered. In particular, to ensure accurate control across an environment not designed for real‐time testing, new higher level control protocols are introduced acting over an optimised communication system. New large time‐step prediction algorithms are used, capable of overcoming both local actuation and distributed system delays. An overview of the architecture and algorithms developed is presented together with results demonstrating a number of current capabilities. Copyright © 2013 John Wiley & Sons, Ltd.     

An ecohydrological approach to predicting regional woody species distribution patterns in dryland ecosystems

This paper presents a quantitative ecohydrological framework for predicting regional distribution patterns of woody species in dryland ecosystems. The framework is based on an existing stochastic model for the daily mass balance of water that represents the interactions between soils, climate, and vegetation. Individual species selection is based on an optimality trade-off hypothesis, which states that dryland vegetation patterns are constrained by maximization of water use and simultaneous minimization of water stress. The relative importance of water use and stress avoidance to the overall fitness of three Acacia species is determined from the heterogeneous basin, the Upper Ewaso Ng’iro river basin, of the central Kenya highlands. The model results indicate that overall fitness is more strongly influenced by water use than stress avoidance but that consideration of both stress avoidance and water use is critical to predicting basin-scale patterns of species distribution. We identify a linear trend in the frequency and intensity of storms with the same annual total using a basin-wide gauge precipitation dataset. After calibration, we apply the basin average linear trends in time for average rain per storm and storm arrival rates. The model results indicate the upslope migration of two species, Acacia tortilis and Acacia xanthophloea to areas with higher total rainfall. Lastly, we explore the modeled changes of species cover in the basin influenced by changes in rainfall total holding growing season rainfall variability constant and changes in growing season rainfall variability holding total rainfall constant. We find that changes in dryland species distribution patterns and relative abundance may be as sensitive to growing season rainfall variability as they are to changes in total rainfall amounts.     

The contrasted evolution of high and low flows and precipitation indices in the Duero basin (Spain)

Abstract

Trends in high and low flows are valuable indicators of hydrological change because they highlight changes in various parts of the frequency distribution of streamflow series. This enables improved assessment of water availability in regions with high seasonal and inter-annual variability. There has been a substantial reduction in water resources in the Duero basin (Iberian Peninsula, Spain) and other areas of the Mediterranean region during the last 50 years, and this is likely to continue because of climate change. In this study, we investigated the evolution and trends in high and low flows in the Spanish part of the Duero basin, and in equivalent or closely-related precipitation indices for the period 1961–2005. The results showed a general trend of decrease in the frequency and magnitude of high flows throughout most of the basin. Moreover, the number of days with low flows significantly increased over this period. No clear relationship was evident between the evolution of high/low flows and changes in the distribution frequencies of the precipitation series. In contrast to what was expected, the number of days with heavy precipitation and the mean annual precipitation did not show significant trends across the basin, and the number of days without rainfall decreased slightly. The divergence between precipitation and runoff evolution was more accentuated in spring and summer. In the absence of trends in precipitation, it is possible that reforestation processes in the region, and increasing temperatures in recent decades, could be related to the decreasing frequency of high flows and the increasing frequency of low flows.

Editor Z.W. Kundzewicz; Associate editor S. Grimaldi

Citation Morán-Tejeda, E., López-Moreno, J.I., Vicente-Serrano, S.M., Lorenzo-Lacruz, J. and Ceballos-Barbancho, A., 2012. The contrasted evolution of high and low flows and precipitation indices in the Duero basin (Spain). Hydrological Sciences Journal, 57 (4), 591–611.     

Uvaichnites riojana: A new crane-like bird ichnotaxon from the lower Miocene of La Rioja (Ebro Basin,Spain)

A new bird ichnotaxon found in Cenicero (La Rioja, Ebro Basin, Spain) is described here. The footprints are preserved in sandstone beds in a central-distal alluvial fringe with a mud-dominated floodplain, located in the transition unit between the Nájera and Haro formations. This level is positioned between the Y and Z local Agenian biozones (lower Miocene). The footprints were preliminarily studied in another work and considered as an indeterminate ichnotaxon. Uvaichnites riojana ichnogen. nov. and ichnosp. nov. is a tridactyl footprint characterized by a prominent central pad, very large to enormous sized, with unjointed toes at the proximal end. These features differ from Aquatilavipes, Aviadactyla, Avipeda, Ludicharadripodiscus, Fuscinapeda, and Ornithotarnocia of the Avipedidae morphofamily. U. riojana is considered to be similar to common crane (Grus grus) footprints in the Gruidae family. There are a few references about this family in the Iberian Peninsula and Balearic Islands and this find could confirm the presence of Gruidae since at least the lower Miocene.     

Effects of climate change on the intensity and frequency of heavy snowfall events in the Pyrenees

The intensity and frequency of heavy snowfall events in the Pyrenees were simulated using data from the HIRHAM regional climate model for a control period (1960?C1990) and two greenhouse emission scenarios (SRES B2 and A2) for the end of the twenty-first century (2070?C2100). Comparisons between future and control simulations enabled a quantification of the expected change in the intensity and frequency of these events at elevations of 1,000, 1,500, 2,000 and 2,500?m a.s.l. The projected changes in heavy snowfall depended largely on the elevation and the greenhouse gas emission scenario considered. At 1,000?m a.s.l., a marked decrease in the frequency and intensity of heavy snowfall events was projected with the B2 and A2 scenarios. At 1,500?m a.s.l., a decrease in the frequency and intensity is only expected under the higher greenhouse gas emission scenario (A2). Above 2,000?m a.s.l., no change or heavier snowfalls are expected under both emission scenarios. Large spatial variability in the impacts of climate change on heavy snowfall events was found across the study area.     

Location of Moderate-Sized Earthquakes Recorded by the NARS�CBaja Array in the Gulf of California Region Between 2002 and 2006

We relocated the hypocentral coordinates of small to moderate-sized earthquakes reported by the National Earthquake Information Center (NEIC) between April 2002 and August 2006 in the Gulf of California region and recorded by the broadband stations of the network of autonomously recording seismographs (NARS?CBaja array). The NARS?CBaja array consists of 19 stations installed in the Baja California peninsula, Sonora and Sinaloa, Mexico. The events reported by the preliminary determinations of epicenters (PDE) catalog within the period of interest have moment magnitudes (M _w) ranging between 1.1 and 6.7. We estimated the hypocentral location of these events using P and S wave arrivals recorded by the regional broadband stations of the NARS?CBaja and the RESBAN (Red Sismológica de Banda Ancha) arrays and using a standard location procedure with the HYPOCENTER code (Lienert and Havskov in Seism Res Lett 66:26?C36, 1995) as a preliminary step. To refine the location of the initial hypocenters, we used the shrinking box source-specific station term method of Lin and Shearer (J Geophys Res 110, B04304, 2005). We found that most of the seismicity is distributed in the NW?CSE direction along the axis of the Gulf of California, following a linear trend that, from north to south, steps southward near the main basins (Wagner, Delfin, Guaymas, Carmen, Farallon, Pescadero and Alarcon) and spreading centers. We compared the epicentral locations reported in the PDE with the locations obtained using regional arrival times, and we found that earthquakes with magnitudes in the range 3.2?C5.0?mb differ on the average by as much as 43?km. For the M _w magnitude range between 5 and 6.7 the discrepancy is less, differing on the average by about 25?km. We found that the relocated epicenters correlate well with the main bathymetric features of the Gulf.     

Trace element mobility in dolomitic argillites of the Mesoproterozoic Belt-Purcell Supergroup, Western North America

The Belt-Purcell Supergroup comprises dolomite-rich stratigraphic units in a dominantly siliciclastic succession, where sedimentation spans 1400-1470 Ma. Dolomitic units are variable mixtures of co-sedimented argillite and primary carbonate post-depositionally converted to secondary dolomite. Based on rare earth element (REE) relationships three distinct REE patterns are identified in the dolomite-rich units: Type 1 (T1d; d = dolomitic sample) with REE patterns parallel to post-Archean Upper Continental Crust (PA-UCC), albeit at lower absolute abundances due to dilution by carbonate content; Type 2 (T2d) with Heavy REE (HREE) enrichment but Light REE (LREE) depletion relative to T1d; and Type 3 (T3d) with enrichment in LREE and HREE relative to T1d, but erratic Middle REE (MREE) patterns. There is a progressive increase of ΣREE from T1d through T2d to T3d, whereas for ΣLREE/ΣHREE T2d < T1d < T3d. T1d-T2d and T3d represent three different “snapshots” of a continuous process.In terms of timing, dolomitization of calcite primary sediment in all samples likely took place broadly during burial diagenesis, as inferred for most Proterozoic dolomites. T1d is easily explained by provenance: however, T2d and T3d cannot be related to provenance, weathering or sedimentary sorting processes to explain higher concentrations of HREE referenced to PA-UCC and consequently developed in the sediment from a T1d precursor. The same three REE signatures have been described in previous studies in counterpart siliciclastic counterparts throughout the Belt-Purcell Supergroup at three different locations. Mobility of normally stable REE is accompanied by mobility of normally isochemical high field strength elements (HFSE) in T2d and T3d to give REE/REE, HFSE/HFSE, REE/HFSE and Y/HREE fractionations. No specific REE-HFSE signatures are apparent in the carbonate-rich units as compared to their non-dolomitic siliciclastic counterparts. This unusual mobility of REE and HFSE reflected in T2d and T3d is attributed to alkaline oxidizing post-depositional brines. Salinity was derived from seawater-sediment reactions, dissolution of evaporite minerals, and the smectite-illite transformation, whereas alkaline oxidizing conditions were promoted by groundwater interaction with mafic units in the basin, CO₂ introduced into the system during episodic rifting with mantle degassing, and interaction of syn-sedimentary mafic intrusions with carbonate units at early stages of BPS deposition. Intermittent brine activity, inducing T2d and T3d patterns, spanned >1 Ga as recorded by secondary monazite grains with age distributions that correspond to large scale tectono-thermal events in Laurentia.Post-depositional processes and redistribution of carbonate can have an impact on transitional stratigraphic contacts between dolomitic and siliciclastic units which may have been incorrectly described as primary due to sedimentary environment changes.