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This is a review of studies related with the effects generated by the fast-growing exotic plantations (PECR) of Pinus radiata and Eucalyptus spp. on water quality of watersheds in south-central Chile, at different spatial and temporal scales. The analyzed data comes from a region between 36° - 40° S in the Central Valley and includes both mountain ranges, the Coastal and the Andes. Studies on the watershed's capacity to export nutrients indicate that the conversion from native forests to forest plantations implies a net loss in nitrogen (N) and phosphorus (P) retention capacity. Consequently, watersheds with plantations coverage experience a net loss of these nutrients. Similarly, in watersheds dominated by Eucalyptus globulus, nitrogen retention decreases, especially NO3-N, and is partially reversed as a wider riparian vegetation is maintained. Studies of soil erosion and sediment transport losses show that clearcut harvesting has significant impacts on water quality, increasing sediment transport rates in streams. However, when soil conservation measures are practiced, erosion rates decrease significantly during forest harvesting. Some of the physical-chemical characteristics of the water, such as pH and temperature, are similar between streams with native forests and forest plantations. There is also a tendency for a decrease of richness and abundance of the macrobenthic invertebrates community due to the replacement of riparian vegetation by Eucalyptus spp. [ABSTRACT FROM AUTHOR]

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Copyright of Ingeniería del Agua is the property of Universidad Politecnica de Valencia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study of sediment transport is important to understand how erosive processes operate on the earth's surface and to try to manage natural resources in an optimal way. This paper studies the mechanisms of surface transport of sediments in two high mountain headwaters that have similar topographic and lithological characteristics with an ecosystem of high ecological value characterized by the alpine grassland. These headwaters are distinguished in that one is in a natural state, located in the Altzomoni gorge, and the other has implemented management practices consisting of the construction of infiltration trenches and afforestation, in the Amalacaxco gorge. Both headwaters are located within the Iztaccihuatl-Popocatepetl Zoquiapan National Park (central Mexico). In the study, the luminescence signals were analyzed with the optically stimulated luminescence (LOE) technique to understand the degree of erosion that exists. The luminescence of the two deposits that make up the surface of the two headwaters was estimated and the LOE signals were analyzed in samples taken on the surface in longitudinal profiles along the slope in three different periods of one year, this to consider the variability associated with seasonal changes. The results indicate that most of the materials that are mobilized downhill come from the surface deposit. However, during the months that concentrate the greatest rainfall and solar radiation, the subsurface materials, more than 80 cm deep, but only in the Amalacaxco gorge, are mobilized punctually. This indicates that erosion is greater in the gorge where the management techniques were implemented, which contrasts with what is observed in the gorge in its natural state. It is concluded that the management techniques applied modify the surface dynamics and favor the incisive processes of the alpine grassland. The use of the method used is appropriate to study erosive processes in high mountain areas. [ABSTRACT FROM AUTHOR]

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Copyright of Boletin de Geologia is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista CIENCIA UNEMI is the property of Universidad Estatal de Milagro (UNEMI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Ingeniería del Agua is the property of Universidad Politecnica de Valencia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ingeniería del Agua is the property of Universidad Politecnica de Valencia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The dune system of Cala Tirant today presents a state of conservation in recovery. Its high dynamism makes accurate photometric identification of blowout morphologies difficult. However, along 350 m of dune front, a total of 7 erosive morphologies can be detected. In this article, corresponding to the field output, the typologies of the different erosive morphologies will be discussed, as well as the operation of a blowout: its aeolian dynamics and sedimentary transport in conditions of strong Tramuntana wind. [ABSTRACT FROM AUTHOR]

In november 2013 the construction of the second bridge over La Restinga lagoon was initiated, a work that seeks to boost transportation to the Macanao Peninsula. Thereafter, a conflict was generated between governmental authorities that proposed this construction, and students and teachers from Universidad de Oriente who demanded the submission of the Environmental and Sociocultural Impact Assessment (ESIA) required by the Venezuelan environmental legislation. On august 13th, 2014, the Governmental authorities publicly presented the ESIA, and indicated that the only negative impact would be the deforestation of 1241 m² of mangroves. However, this study shows that the environmental impacts were greater than those indicated by authorities. To support this, satellite images were used to calculate the deforested area and to find out other changes in the components of the landscape. Sediment traps were also placed in the main channel to assess the contribution of exogenous material into the lagoon. It was estimated that the deforestation of mangroves comprised an area of 2399 m², 892 m² of the main channel were invaded by gravel-clay material and 639 m² in the adjacent lagoons. Sedimentation was homogeneous during the study period, but occurred mainly in the construction area and on occasions was greater in other zones at the mouth of the lagoon. It is recommended a long-term sediment transport evaluation be performed, as well as the monitoring of the health and survival of mangroves and marine organisms susceptible to sedimentation, especially of filter feeders. [ABSTRACT FROM AUTHOR]

In this work the potential rate of sediment transport in Oasis beach sector, of Varadero beach, was determined. For this many variables were taken into account such as climatic, oceanologic, hidrologic, geographic, bathymetrical and sedimentological ones, specially the latter one. All selected beach profiles are described and which of them were included into the sediments statistics. Causes of erosion were established. Each type of sediment transport was modeled and quantified using different methods: analytical, estimation and numerical models as XBEACH and Delft 3D. [ABSTRACT FROM AUTHOR]

An aggregated model to estimate mean denudation rates of tropical mountain basins with limited data is presented, which is calibrated for Antioquia (Colombia); based on the transport equation of Engelund-Hansen. Two complementary approaches are purposed: (1) alluvial river reach model, dependent on discharge, slope and hydraulic geometry and (2) hillslope model dependent on discharge minus base flow, slope, drainage density and flow convergence degree. Both models are closed with a regression for the Shields parameter, depending on sediment yield (t/km2/yr) and an erodibility factor, which is considered robust due to the diversity of scale, morphology and weather of the 23 basins analyzed. Both model approaches predicts inside a +/- 50% margin of error the sediment yields of 70% of the basins, those with less peculiarities; correcting it with a bed load portion, additional to the suspended transport measured, analytically estimated and proved with field data. [ABSTRACT FROM AUTHOR]

This article shows the results of the hydrologic analysis of watersheds of rivers Sinú, Aracataca, and Foundation. The characteristics and variability of river inputs (flow and sediment transport) and historical trends to identify regional patterns in fluvial dynamics were evaluated. Records of flow and sediment transport were taken of the Institute Hydrologic and Studies Environmental (IDEAM), to perform a statistical analysis of the time series of sediment transport and flow. Sediment transport and stream flow, were show highly dependent, while the dual-mass curves helped to identify the influence of external factors on sediment transport. The dynamic of the basins Fundación and Aracataca, showed maximum events with return periods of 2 and 10 years, while the Sinú River fluvial dynamics was maintained regular due to the influence URRÁ dam. The basins were subject to weather conditions equal, which explains the behavior recorded. [ABSTRACT FROM AUTHOR]

In this work Los Taínos beach, in Varadero, is characterized taking into account sand grain patterns, incident wind and its directions. It was made in such a way that monthly and annual behaviour of wind sediment transport capacity can be determined applying several mathematical expressions. Selection of the design year with respect to wind data was an important step, which establishes main directions of attack for this coastal segment. Also, wind-blown transport toward dunes for all the study area was determined. [ABSTRACT FROM AUTHOR]

Fluvial deposits contain mineral grains that are exposed to solar radiation during their transport in the water column. Traditionally, the Optically Stimulated Luminescence (OSL) method has been used in geomorphology to date sediments that have been exposed to sunlight prior to their deposition. A new approach of OSL consists in using luminescence signals of sediments to unravel the mechanisms controlling sediment transport, regardless of whether or not the grains were fully exposed to sunlight before deposition. The main goal of this paper is to exemplify with two case studies on the use of luminescence signals to unravel how sediments are transported in two geomorphic domains. We studied the Sierra de Gredos (Spain) and the Cadder dam (Scotland) where we analyzed debris low and luvial deposits respectively. The luminescence signals in Sierra de Gredos allowed us to distinguish luvial sediments from debris low deposits. In Cadder we observed an inverse relation between grain size and the intensity of luminescence. We propose that the new approach of OSL in geomorphology is a useful tool in understanding the mechanisms of sediment transport in the study of luvial sediments. [ABSTRACT FROM AUTHOR]

On the north shore of the Bahia Blanca estuary, Buenos Aires, Argentina, sand shell ridges composed by a high proportion of boulders of sedimentary origin are present. Many of these clasts show significant signals of bieorosion. The procedence of this material is linked to the extensive abrasion platforms present to the east of the estuary (coasts of Pehuén Co). Two ichnofacies were established: Trypanites ichnofacies comprising Gastrochaenolites, Maeandropolydora, Trypanites, Gnathichnus and Radulichnus, typical of hard substrates and Skolithos ichnofacies represented by Ophiomorpha galleries developed in soft substrates. Both characterize a shallow coastal environment. During the Holocene transgression, coastal substrates were affected by the advancing sea and eroded fragments were transported by littoral drift into the estuary. Finally, storm events deposited material with signs of bioerosion in the littoral ridges. Today, many of these boulders, which exhibit gradations in size into the estuary, are in transit across the beaches by east-west littoral drift. [ABSTRACT FROM AUTHOR]

Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We studied the spatial distribution and textural characteristics of 234 surface sediment samples from the Bay of Cartagena, Colombia, to understand sedimentation processes over the last few decades. We used three discriminant functions to characterize depositional environments and to differentiate among: (i) beach deposits and sediments of high-energy, shallow marine environments, (ii) fluvial deposits and sediments of shallow marine environments, and (iii) fluvial deposits influenced by turbidity currents. The predominant sediment type is a medium-size (5.35 ± 1.2 φ), poorly sorted (σ = 1.63 ± 0.8) mud, with a noticeable asymmetry (Sk = -0.052 ± 0.2) and kurtosis (k) of 0.84 ± 0.4. There were two main superficial sediments types in the Bay of Cartagena: (1) sediments of high-energy, shallow marine environments with high fluvial influence, and (2) turbidity current deposits with high fluvial influence. Sediments with the lowest sand content (<5%) are located along a latitudinal axis running from the Dike Channel prodelta to the western end of Tierrabomba Island. The CaCO3 content of the sediments is <10%. Autogenous calcareous sediments are covered by fine terrigenous sediment transported through the Dike Canal, which has a more active and dominant role in the Bay's sediment deposition than previously reported. [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent years, the use of optical (Optical Backscatter Sensor, OBS) and acoustic (Acoustic Current Doppler Profiler, ADCP) instruments has allowed monitoring the temporal and spatial variation of the suspended sediment concentration (SSC) in coastal and estuarine environments with greater resolution. However, the development of the application of those techniques in tropical environments is incipient. For this study, an OBS-3A calibration procedure was implemented, taking dry and desegregated sediment from the study zone as a calibrating pattern. Moreover, we present the corrections required for the ADCP signal to be useful in the estimation of SSC due to geometrical spreading, the attenuation of sound by water, and the particles in suspension. The ADCP and OBS-3A were used to measure SSC in the Mira River delta system (Morro Island and principal river mouth), located on the Pacific coast of Colombia, a coastal tropical environment where some oceanographic and estuarine factors determine the signal response of the instruments. [ABSTRACT FROM AUTHOR]

The morphology of a submarine dune field developed in a tidal inlet that connects the Argentinean continental shelf with Anegada Bay (southern Buenos Aires province) was studied. The sediment circulation was inferred from the differential displacements of the bedforms evaluated by comparing consecutive surveys. An echosounder and a Phase Measuring Bathymetric System (PMBS) called GeoSwath were used to obtain a detailed submarine morphology. Large dunes, with heights between 4.5 and 5.0 m and from 100 to 120 m separating them, were present near the southern limit of the dune field at 24 m depth. These dunes move towards the outer part of the channel at a speed of 18 to 75 m year-1. At the northern end of the dune field, at 21 m depth, the dunes are smaller, being 2.0 to 2.5 m in height and separated by 40 to 80 m. The smaller dunes move towards the interior of Anegada Bay at 18 to 36 m year-1. The distribution of the water flow in the entire water column was obtained through a perpendicular profile of the channel by means of an ADCP. Maximum current speeds were 2 m s-1, and were found during flood tide. The results obtained indicate a circulatory transport model of sedimentary sands, with the formation of ebb and flood deltas at both ends of the deep inlet throat, which lacks of unconsolidated sediments. [ABSTRACT FROM AUTHOR]

The grain-size trend analysis (grain size, sorting asymmetry) was determined at 58 stations in order to infer the residual vectors of sediment transport in Magdalena Bay, Baja California Sur, Mexico. Grain-size trend analysis and principal components analysis were applied to textural sediment parameters. The results indicated that well-sorted sediment is associated with fine to very fine sand. The residual vector transport suggests the presence of two gyres in the dispersion of clastic material: (1) acyclone-ic gyre in the deeper, central part and (2) an anticyclone-ic gyre in the southeast part of the bay. The sediment transport pattern is highly correlated with the residual tidal currents in Magdalena Bay. [ABSTRACT FROM AUTHOR]

This paper shows a methodological proposal to carry out river morphology analysis and sediment transport for urban basins highly intervened by human actions. In this methodology, different activities that will allow doing a detailed analysis for the river morphology and sediment transport in the basin are proposed. Among the steps proposed to implement this methodology, there are: analysis in plant of little basin, altitude profiles analysis of the main sub-basins, field measures (measures of liquid and solid discharge and general observations of the basin morphology), and estimations of sediments load and bed load capacity in the stream. An application to basin of Doña Maria is showed. [ABSTRACT FROM AUTHOR]

Sand and gravel mining on rivers causes erosion or incision of the river bed, upstream erosion in tributaries, damage to different structures (bridges, water intakes, dykes, bank protection works, houses and roads), and, it alters the river equilibrium, affecting the fluvial ecosystem. In order to minimize the negative effects a methodology is proposed for estimating the maximum annual extraction volumes, based on the annual sediment transport of the river, in other terms, on the natural replenishment rate. Initially it is important to carry out an integral study of the river to understand the fluvial dynamics, including the different aspects (hydrology, hydraulics, sediment transport.) with emphasis on the geomorphologic processes and the identification of other aspects (dams, intakes, protection works.) that could be affecting it. The possible areas of aggradation should be estimated, this is, the areas that are potentially exploitable, and the morphological changes due to the mining activities should be estimated. The proposed methodology also requires a periodic monitoring of the bed load and of the variation of the river bed levels, the updating of the annual sediment loads duration curve and the forecasts of the river discharges for a given year. [ABSTRACT FROM AUTHOR]

Copyright of Ingeniería Hidráulica en México is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ingeniería Hidráulica en México is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This articles presents an analysis of the historical framework of landscape evolution models, specifically erosion models: it also refers to the current state of the art from which critical analysis derive the fundamental aspects which should be taken into account in the formulation of an erosion model in catchment scale. The theme is introduced with a brief review of the evolution of knowledge of landscape evolution models, which provide the overall framework of erosion models. From this analysis, basic questions to be addressed by an erosion model arise. Later, analysis of the historical development of erosion models is made; It also summarizes the main characteristics of the current erosion models and lists potentialities and limitations of erosion models. This paper corresponds to a literature review aimed at defining the theoretical framework of a research project entitled "Development of an Erosion, Transport and Sedimentation Conceptual Model." [ABSTRACT FROM AUTHOR]

Bahía Blanca estuary located in the south of Buenos Aires province, Argentina, is characterised by a low coastal area with large tidal plains, islands, and a complex network of tidal channels of different dimensions. The latter form an interconnected tidal channel system. The aim of this study was to determine the net bedload sediment transport in an interconnected channel system (Cabeza de Buey, El Alambre, La Lista, and Principal channels) through an analysis of the morphological features of the bottom using acoustic dat (echosounder and side scan sonar). Cabeza de Buey channel is connected to La Lista channel through El Alambre channel. The first two flow into the Principal channel. Cabeza de Buey channel has a flat bed of mud with very fine sand and medium-sized dunes of fine sand in its inner sector that display an asymmetrical section according to the ebb flow. These dunes continue to develop uninterrupted towards El Alambre channel, where large dunes (1.5 m high) of very fine sand originate. Their crestlines are either sinuous or barchanoid and they have their lee towards the ebb current. In La Lista channel, medium-sized asymmetrical dunes and large sand ribbons form on a rocky bottom according to the ebb flow. The sediment mobilized by the currents is characterized by the fine sand - silt fraction. The distribution and configuration of bed forms reveal that the bedload sediment transport is mainly concentrated in La Lista channel. Thus, only one tidal channel regulates the dispersal of sandy material, transporting a significant volume of sediment towards the shipping channel. [ABSTRACT FROM AUTHOR]

To determine residual sediment transport in the Bay of Todos Santos (BTS), grain size trend analysis were compared and applied utilizing models of Sunamura and Horikawa (1971), Mc Laren and Bowles (1985), and Gao and Collins(1994). The Sunamura-Horikawa model uses grain-size and sorting for comparison criteria to infer sediment transport whereas the models of Mc Laren-Bowles and the Gao-Collins use these two parameters and also asymmetry. The first two models mentioned are one-dimensional while the third model is two-dimensional. The model of Gao and Collins (1994) turned out to be most satisfactory model for determining patterns of dispersion of surface sediments. In the BTS, the pattern of dispersion showed several sediment transport tendencies. In the North zone of the bay the transport was in a SE direction (following the isobath contour of 20 m), and towards the NE (near the Island of Todos Santos). For the South zone transport displayed a NE direction, while the central region of the bay displayed a westerly transport direction. In the canyon of Todos Santos a NE trajectory was determined. The presence of currents with speeds of 0.30 ms-1 makes transport possible towards the interior part of the bay. In the external region of the bay, in front of the Islands of Todos Santos and the Peninsula of Punta Banda, the inferred transport is towards the W. For the shallow zones, the superficial circulation and the coastal transport agree with previous published results and compare well with the present work. The tide processes (current residuals or internal waves) are an important factor in the resuspension and transport of material in the deep zones of the bay. The central zone of the bay seems to be a convergence site and can give rise to particle stagnation in the bay (e.g., polluting agents). [ABSTRACT FROM AUTHOR]

The environmentally advanced societies are claiming progressively an authentically integral fluvial management, that implements Watershed Management Programs based on the paradigm of the Environmental Flows Regime (EFR). This work suggests a generic methodology for the reliable EFR setting, that facilitate the water use with an environmental acceptable cost. Additionally, it outlines the approaches and outstanding techniques for the evaluation of instream flow requirements, which constitute the EFR by means of the Instream Flow Regime (IFR). The adaptation of these approaches to the Colombian rivers will contribute to the conservation of their valuable biodiversity. [ABSTRACT FROM AUTHOR]

Today, beaches are in a critical situation due to erosion. These places are very significant for the economy and tourism. For this reason is important to know the rate of sediment transport and the behavior of it. This work proposes a methodology based in used international models to estimate magnitude and direction of the littoral sediment transport. The method that expose propose to use Longuet-Higgins's velocity formula in Bijker's method to obtain cross shore distribution of alongshore sediment transport. Even, values in surf zone are required for this, it can solve through methodology shown in Coastal Engineering (2000) of Technical University of Delft. Calibration is make for two study. [ABSTRACT FROM AUTHOR]

Every three months during 2002, a 1/8-m2 Technicap PPS-3 time-series sediment trap was moored 50 m above the bottom of Alfonso Basin and provided 7-8 day resolution. Under the dissecting microscope, marine snow was abundant, while fecal pellets varied in number, size (0.25-10 mm) and form. Centric diatoms were common year-round, while chain-forming diatoms were clearly abundant only during a two-week period in June. The bulk samples were sieved (1 mm) to remove swimmers, the most frequent being polychaetes and pteropods, followed by gelatinous organisms and, rarely, crustaceans. The material was separated into ten equal parts using a rotary splitter. Four of the splits were rinsed of seawater, dried and weighed to determine the total mass flux. This varied between 0.17 and 2.48 g m-2 d-1. The highest fluxes occurred in February and the lowest in mid-April and late June. The average mass flux (300 g m-2 yr-1) is equivalent to a sediment accumulation rate of 0.4 mm yr-1, similar to that obtained from the dating of sediment cores from the basin. The carbonate fraction, determined by coulometry of the carbon content before and after acidification, was considerable, accounting for 8-26% of the total. The mean (14.6%) is similar to the concentration reported for surficial sediments. Peak concentrations occurred during periods in January, March, May, October and November. The CaCO3 flux averaged 0.128 g m-2 d-1, ranged between 0.036 and 0.304 g m-2 d-1 and was most intense in autumn and winter. The total mass and carbonate fluxes in La Paz Bay are considerably greater than those observed in Guaymas Basin, in the open Gulf of California. [ABSTRACT FROM AUTHOR]

The spatial and temporal variability of the beach-line position at the tidal inlet of Punta Banda coastal lagoon in Baja California, Mexico, is described from the analysis of ten aerial photographs and two satellite images spanning from 1972 to 2003. The results showed that the maximum tidal inlet width (995 m) occurred in 1980. Changes observed from 1980 to 1985 suggest that the extraordinary sediment fluxes that occurred during the winter storms of 1977/78, 1980/81 and 1982/83 were the main source of sediment inducing the growth of the sediment structures that delimit the tidal inlet. By the end of 1985 a new sand bar appeared on the northern side of the tidal inlet and its formation is attributed to a reduction in the ebb and flood tidal intensity as a consequence of the combined effect of the increase in width of the tidal inlet in 1980, of the extraordinary supply of sediments and of the dominant northeast to southwest longshore sand transport. The net growth of the sand bar that shapes the southern side of the tidal inlet was 53 ha from 1978 to 2003, of which 26 ha are located in the inner part of the tidal inlet. This growth and consequent reduction of the tidal inlet could be the result of a reduction in the tidal prism produced by the great amount of sediments supplied to the coastal lagoon by storms and also by the reduction of the lagoon's flushing capacity. [ABSTRACT FROM AUTHOR]

Material from the bottom and banks of very shallow channels can be eroded due to current effects, producing suspended sediments that are transported by water movement. The problem with sediment transport in these systems can be dealt with using the transport equation, where the particle flow is calculated as a function of the sediment characteristics and of the flow itself. However, the parameters are complicated when the channels consist of cohesive matter. In this paper, a procedure based on the experimental determination of the parameters is proposed in which the erosion and deposit terms are valid for cohesive and non-cohesive silt. This method can be applied to those systems where suspended sediments originate mainly from the erosion and deposition of spring sources. The application of this method to the Sancti Petri Channel allows us, based on simultaneous recordings of current speed and concentration of sediments in suspension, to calculate the critical velocity for this system, which is formed by cohesive matter. The Sancti Petri tidal system is an inflow-outflow channel that extends from the inner zone of Cadiz Bay to the outlet to the Atlantic Ocean. It is approximately 17 km long and has a deep central zone, fringed with ample muddy areas, where the currents associated with tides reach high intensities. [ABSTRACT FROM AUTHOR]

The object of this paper was to evaluate the efficiency of the Ammophila arenaria in catching sediments. It was made by comparing sectors with dense vegetation cover and bare dunes (blowout), on foredunes at the central coast of Chile (38°05′S). Vertical sand traps were placed across transects at the beginning of the dune formation, and at the base and the top of the foredune, in order to determine the aeolian sediment transport rates. The results showed that in the windward slope with dense vegetation the sand grains were trapped and an insignificant amount (3%) advanced behind the dunes. On the other hand, on the blowout, the sand windblown increased exponentially to the top reaching values up to 447% with respect to those found at the base of the blowout. The great capacity of the Ammophila arenaria in catching sediments is verified and it considers that foredunes with dense covers of Ammophila arenaria are like true natural traps for the evaluation of aeolian sand transport rates. [ABSTRACT FROM AUTHOR]