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The estuary of the Rio Jaguaribe (NE Brazil) is filled by a sediment sequence of more than 23 m and characterised by estuarine plains that – today - extend 30 km upstream. We investigated the sedimentary dynamics in the Rio Jaguaribe estuary since the early Holocene by means of clay mineralogical analyses, as well as sediment analyses from 11 sediment cores. The clay mineralogical approach proves to provide the most robust results. A transition of the illite/kaolinite peak area ratio from 0.3 to 1.8 within the vertical depositional record suggests a change of sediment transport direction over time. Whereas in the lower sequence marine influence dominates, characterised by the relatively high kaolinite content originating from the weathered Barreira formation at the coast, in the upper sequence sediments of fluvial origin dominate, which are characterised by the relatively high illite content originating from the crystalline rocks in the source area of the Jaguaribe river. The depositional architecture of the Holocene sediments of the Jaguaribe estuary shows a seawards prograding infill, assumed to have occurred since the mid-Holocene and supports studies suggesting a stagnating or slightly falling relative sea level (RSL) since ∼7000 BP. • Within the estuary sediment infill a transition from low illite/kaolinite to high illite/kaolinite ratios is documented. • Clay mineralogy is a robust tool for defining changes of dominant sediment pathways in an estuary. • The change from marine ingression to progradation of the estuary is assumed to correlate with RSL change around 7000 BP. [ABSTRACT FROM AUTHOR]

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The Meaípe-Maimbá embayed beach (MMEB) on the south-east coast of Brazil has been subject to anthropogenic pressures since the 70's. In this study we discuss the adequacy and contribution of the parabolic planform model to determine the planform and variability of the MMEB, taking into consideration variation in wave conditions. The role of different controlling conditions on the planform variability is analyzed, as well as the morphological and planform mobility. MMEB exhibited a new configuration in response to the construction of a harbor, which interrupted the longshore sediment transport. After four decades, three particular morphodynamic sectors have been recognized along the beach. The central sector is more exposed to normal wave incidence and cross-shore processes predominate. The northern and southern sectors are influenced by wave diffraction processes around the headlands and port, respectively. In the northern sector, the presence of secondary headlands and inner islands imposed a geomorphological control on beach morphology and coastal processes. The use of the parabolic planform model provided useful insights for the assessment of potential planform mobility, since the decadal shoreline evolution combined with beach profiles and sediment characteristics allowed understanding of the beach mobility processes and supported the interpretation of modeling results. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines the role of coastline orientation on foredune and dunefield development at Moçambique Beach, Southern Brazil. The beach displays significant alongshore variations in exposure to the prevailing winds and waves, grain size, beach/surfzone morphodynamic type, foredune volume, and type and dimensions of the Holocene dune systems. Two wind analyses and calculation of aeolian drift potentials were carried out, one based on 1year of wind record and another based on a record of 34years. Monthly topographic surveys of beach and foredunes on 5 profiles along Moçambique beach were conducted over one year to obtain data on beach mobility and width, aeolian sediment transport and foredune development. Southerly winds dominate, and aeolian sediment supply is minimal in the south, moderate in the central portion and high in the northern portion of the embayment. The relationship between actual sediment supply, foredune building and potential sediment supply is relatively poor over one year due to factors such as beach type and mobility, beach moisture levels, rainfall, storm surge and wave scarping. The intermediate term (34year) record indicates a strong relationship between foredune size and volume, winds and shoreline orientation: foredune volume is minimum in the southern part of the beach and greatest in the northern part of the beach. The Holocene barrier and dunefield development also reflects the long term control of shoreline orientation and increasing longshore gradient in exposure to southerly winds: for the last 6000–7000years a small foredune developed in the southern portion, parabolics and small transgressive dunes in the central portion, and a large-scale transgressive dunefield in the northern portion. [Copyright &y& Elsevier]

A port complex was implanted in the coast region of Suape, PE-Brasil, in 1979–80, which altered the geomorphological and hydrodynamic conditions of the area, mainly in the estuary of the Ipojuca River. Water samples were collected from the surface and the deep layer to determine the salinity, pH, dissolved oxygen, transparency, and temperature from three fixed stations in the estuary of the Ipojuca River during the summer and winter before (1978) and after (1986–87) the port's construction, in order to evaluate the effects of the port-induced changes. The data were subjected to a principal component analysis and to individual t tests. The first principal component, the axis of maximum information, alone explained 50% of the total variance, being associated with the generalized increase of the chemical parameters after the port's construction, mainly the salinity. Despite the fact that the results of the t tests presented significant differences only for the dissolved oxygen, pH, and temperature, the increased salinity produced the greatest ecological effects in the estuary. The water flow of the Ipojuca River was diverted toward the ocean, decreasing the river-flow velocity at the mouth. This decrease in flow caused a sedimentation in the area, a decrease in the circulation and depth, and a transformation of the mouth of the river into a coastal lagoon with an increase in evaporation and salinity. A delay of more than 2 hours was observed in the dynamic tide in relation to the normal 6-hour cycles. Despite an increase in the concentration of dissolved oxygen and transparency values, effects that theoretically improve environmental conditions, a morphological transformation occurred that caused drastic changes in the estuary's circulation and in the tidal currents. [ABSTRACT FROM AUTHOR]

• Nonoccurrence samples acquisition is relevant to resulting susceptibility maps. • ANN models can lose generalization ability if training set is too easy to classify. • Using only easy-to-classify nonoccurrence samples affects maps negatively. Landslide susceptibility assessment using Artificial Neural Networks (ANNs) requires occurrence (landslide) and nonoccurrence (not prone to landslide) samples for ANN training. We present empirical evidence that a priori intervention on the nonoccurrence samples can produce models that are improper for generalization. Thirteen nonoccurrence cases based on GIS data from Rolante River basin (828.26 km2) in Brazil are studied, divided in three groups. The first group was based on six combinations of buffers with different minimum and maximum distances from the mapped scars (BO). The second group (RO) acquired nonoccurrence only from a rectangle in the lowlands, known for not being susceptible to landslides. For BR, six alternatives respectively to BO were presented, with the inclusion of nonoccurrence samples acquired from the same rectangle used for RO. Accuracy (acc) and the Area Under Receiving Operating Characteristic Curve (AUC) were calculated. RO resulted in perfect discrimination between susceptible and not susceptible to landslides (acc = 1 e AUC = 1). This occurred because the model simply provided susceptible classification to points in which attributes are different from those in the rectangle, harming the classification of nonoccurrence sampling points outside the rectangle. RO map shows large areas classified as susceptible which are known to be non-susceptible. In BR, sampling points from the rectangle, which are easy to classify, were added to the verification sample of BR. Average acc for BO 00 m (minimum buffer distance to scars of 0 m): 89.45%, average acc for BR 00 m: 92.33%, average AUC for BO 00 m: 0.9409, average AUC for BR 00 m: 0.9616. Maps of groups BO and BR were alike. This indicates that metrics can be artificially risen if biased samples are added, although the final map is not visibly affected. To avoid this effect, the employment of easily classifiable samples, generated based on expert knowledge, should be made carefully. [ABSTRACT FROM AUTHOR]

The objective of the present work was to analyze the bottom morphology, the genesis of the bedforms, and the patterns of current and sediment transport of the internal portion of the south mouth in Paranaguá Bay, Paraná - Brazil. This region was used as a laboratory field to study the geomorphology of a dune field on a tide channel, with features of flood delta in the inner portion and ebb delta in the direction of the continental shelf. A sediment hydrodynamic model was used to calculate the direction and magnitude of the sediment transport and the residual current flows. A map of apparent roughness was used in the numerical model, obtained through the soundings of a sidescan sonar (Starfish Sonar) and estimated from the classification of the dune field, so it is possible to obtain simulations with higher correspondence with reality. It was observed two vortices of residual circulations near the shores of Pontal do Sul and Ilha do Mel, with directions towards the continental shelf. The residual circulation vortex is responsible for the triangular shape of the large dunes near the Pontal do Sul margin. In the flood, the sediment material is conducted inward forming small ripples and accumulating sediment material on large dunes. During the ebb, these ripples are supposedly destroyed and attached to the large dunes or to the water column. On the other hand, the bedforms of Saco do Limoeiro are formed due to the effects of the tide when entering the mouth and the confinement of the water mass in the region until the next moment of padding. • The bedforms and the sediment transport of the south mouth of the Paranaguá Bay were investigated. • The residual current vortices are responsible for the superposition of small ripples in the dunes and also by its shape. • At Saco do Limoeiro was demonstrated how the bedforms could lead to a false interpretation of geomorphologic evolution. [ABSTRACT FROM AUTHOR]