Revista Brasileira de Geomorfologia

Morphological changes in the lower estuarine coastal sector and socio-environmental impacts – Amapá: between 1992 and 2022

2024-11-12T16:21:45-03:00

Coastal regions are transitional areas between terrestrial and marine environments, with dynamic ecosystems, high biodiversity, economic productivity, population density and environmental fragility. The Amapá Coastal Zone is 800 km long and is influenced by atmospheric and oceanographic agents as well as the Amazon River. The study examined the variation between erosion and accretionary processes and their consequences, such as loss of infrastructure, lack of energy and increased saline intrusion in communities between the Gurijuba and Araguari rivers, including the Bailique archipelago. The physiographic characteristics, fieldwork and a multi-temporal series between the years 1992, 2005, 2014 and 2022 were analyzed. It was identified that 60% of the area presents accretion processes, represented by the formation of muddy banks, tidal flats and the clogging of the mouth of the Araguari River, while 40% suffers erosion, affecting 14 of the 20 monitored communities, highlighting the opening of drainages and modification of hydrodynamics. The deficiency in the management of these modifications has generated isolated and ineffective mitigating actions, aggravating the effects of erosion and wasting resources. If current trends are maintained, including forecasts of increased extreme weather events and sea level, more losses will occur, causing irreversible changes in local morphology and hydrodynamics in the short term.

Rivers channelization and the (dis)continuos geomorphological effects on the fluvial system of the Macaé River - RJ

2025-02-12T15:32:55-03:00

Hydraulic engineering works play a critical role in altering the natural behavior of a river landscape. One of the most common interventions is channelization, which directly entails the widening and deepening of the riverbed and modifying the channel's cross-sectional geometry. In Brazil, this type of work has often been conducted in floodplain areas and urban centers to ensure basic sanitation and promote economic activities. Despite its widespread use, there is a significant gap in research focused on the effects of these works on the evolution of river environments. From a geomorphological perspective, this intervention can trigger a series of changes in the pattern of hydrosedimentological processes in the river system, not limited to the altered segments. This study discusses the impacts of river channelization on the Macaé catchment, from a geomorphological approach and the recent trajectory of channel evolution. The results suggest that the intervention has intensified upstream erosion processes, characterized by rapid vertical incision of the riverbed, increased bank erosion with terrace exposure, and migration of meanders towards the channelized areas.

Relationship between soil, relief, and parental material in the Devonian Escarpment – Ponta Grossa – Southern Brazil

2025-03-20T17:10:08-03:00

The Devonian Escarpment (South Brazil) has developed in a very peculiar area, in the transition between the First (basement) and Second (Paraná Sedimentary Basin) Paranaense Plateaus. Considering this complex geological-geomorphological framework, this study aims to understand the relationship between soil, relief, and lithology in a sector of this area, in Ponta Grossa (Paraná State). Together with geological information, Copernicus elevation data were interpreted in order to divide the study area into morphopedological units, for which the probable soil cover could be inferred. Subsequently, field work was carried out to describe soil profiles and collect samples to perform granulometric and chemical analyses. On the top of the Second Plateau, Neossolos Litólicos Húmicos and Hísticos [Leptosols (Histic, Humic)] dominate due to the presence of headwaters and closed depressions, whose origin is related to mineral dissolution caused by organic acids. Cambissolos Háplicos [Cambisols] and Latossolos Vermelho-Amarelos [Clayic Ferralsols (Ferritic, Rhodic)] occur in interfluves where there are no headwaters and closed depressions. In the First Plateau, Argissolos Vermelho-Amarelos [Acrisols (Ferric)] associated with Cambissolos Háplicos [Cambisols] dominate on the slopes, while in the flat-bottomed valleys, Gleissolos Háplicos [Gleysols] associated with Cambissolos Háplicos [Cambisols] occur. In the Escarpment Front, Neossolos Litólicos [Loamic Leptosols (Cambic)] with low concentration of organic matter dominate over metamorphic rocks due to the presence of very steep relief.

Depositional processes and the formation of the paleontological and archeological record at the Lagoa dos Porcos site, Southeastern Piaui

2025-04-03T12:31:16-03:00

This article addresses the processes involved in the formation of Quaternary sedimentary deposits at the Lagoa dos Porcos site, with emphasis on stratigraphic analysis, with the aim of providing new contributions on the depositional processes involved in the formation of the paleontological and archaeological record of this shallow lake, located in the Serra da Capivara Archaeological Area, in the semi-arid region of Piauí. The research method used a combination of granulometric analysis, verification of morphological properties, radiocarbon dating (AMS) and optically stimulated luminescence (OSL) in samples of sediments and carbonate nodules from stratigraphic profile 4. The data obtained indicate that the lake holds information reflecting at least four periods of deposition related to the Pleistocene, the Pleistocene/Holocene transition, and the early and recent Holocene. Regarding the source area of the paleofauna bones and archaeological material, it is proposed that they came from the surrounding areas, such as the pediment ramps and ancient terraces.

Mountains of the intertropical passive margins and their cartographic representation: methodological proposal in different litostructural arrangements

2025-02-17T08:18:47-03:00

The core hypothesis of this article considers that methodological approaches related to geomorphological cartography must seek standardization based on landscape types. Thus, a methodological proposal for geomorphological cartography in mountainous landscapes is presented, with demonstrations in compartments structured in three distinct lithostructural bases located in the context of Serra da Mantiqueira: nepheline-syenites, gneiss-granites and quartzites. The results showed a similar geomorphological organization for the different compartments, admitting the same methodological approach and the adoption of a unified legend, since the geomorphic facts found were convergent, despite the differences in the geological bases between the areas. It is postulated that the methodological approach presented can be applied to different geomorphological contexts located in the large escarpments of the intertropical passive margins, thus making the universalization of interpretative and technical procedures compatible with the also universal character of this landscapes.

The development of erosion features in cuesta relief regions

2025-02-04T15:13:53-03:00

The cuesta relief is characterized by high slopes, colluvial deposits and intense evolutionary dynamics, making the
region especially prone to soil degradation. This study intends to identify how the relief, lithology, and soils influence the
occurrence of linear erosion processes of rill erosion, ravines and gullies in the cuestas environments. For that, the density of
linear erosion features of 1972 and 2010/2011 were mapped and then analyzed in comparison with the mapped morphological
features of the Cuesta in Botucatu, also prepared in this study, and lithological and soil maps from secondary sources.
Quantitative and qualitative analysis identified concentrations of gullies in the cuesta reverse, at drainage headwaters, close
to lithological contacts and over latosols. On the cuesta front, concentrations of rills, ravines and small gullies were identified,
driven by the steep slope, colluvial covers, and transitions of heterogeneous lithologies and soils. The data demonstrated that
lithological and pedological transitions, typical of cuesta regions due to high geodiversity, in addition to other conditions, are
factors that enhance erosive dynamics and must be considered in territorial planning in order to preserve soils and other
natural resources of these regions

Hydrosedimentary dynamics and morphological features of a rocky channel bend: Piquiri River, PR, Brazil

2025-02-03T07:18:10-03:00

The size and geometry of alluvial river bends are a result of the stream power and the sediment load. However, the efficiency of these variables is not the same in rivers over rocky substrates. Considering the hypothesis that a channel bend influences the flow dynamics and characterizes specific flow zone conditions, bed morphology, and sediment load distribution, the objective of this study is to characterize these variables in a rocky-bottom controlled bend of the Piquiri River, PR, Southern Brazil. The methods used for this were: a) Field data collection (bottom and suspended sediments, bathymetric Esurveys, and flow discharge and velocity); b) echosounder and ADCP data were processed by the ArcGis 10.4 and VMT (Velocity Mapping Toolbox) software; and c) Laboratory procedure (quantification of suspended and bottom sediment). The results demonstrate that the bottom morphology and channel curvature influence the depth variation, highlighting the increase in depth in the downstream section of the bend, as well as in the flow distribution and velocity with the generation of helical cells in the channel bend zone. The concentration of suspended sediment varies, both from upstream to downstream, as well as at different depths, being, however, significantly higher downstream of the bend. These results denote great importance in understanding the dynamics and flow processes in channel bends with rocky beds, with emphasis on the behavior of the flow with different pressure gradients.

How have bridges and culverts changed rivers? A scientometric investigation

2025-03-17T15:51:44-03:00

Bridges and culverts play a crucial role as connectors between river banks. However, these crossing structures alter sediment transport, flow regime, and river morphology. In this study, the aim was the scientometric analyses of studies on the morphological changes in fluvial landscapes caused by bridges and culverts with an analysis of the quantity and global distribution of scientific production. These analyses demonstrate that there is a geographical gap in characterising and quantifying geomorphological alterations. It is necessary to focus the need for additional research in diverse regions worldwide that quantify and characterises geomorphological changes according to the type of structures and their spatial distribution in the river, i.e., understanding how alterations occur upstream and downstream of the structures. Furthermore, it emphasises the importance of interdisciplinary collaboration between fluvial geomorphology and river engineering, which can enhance the development of new structural projects.