<p>The river system plays a very important role in denudation processes and, consequently, in relief evolution in non-glacial landscapes. Several theoretical and empirical studies have contributed to a better understanding of how rivers change after modifications in their boundary conditions, such as tectonics or climate. The region of the Middle Valley of Para&#237;ba do Sul (MVPS) has important records of recent drainage captures, which show a state of transition of the landscape and, consequently, a reorganization of the drainage networks. This region is in the Southeast of Brazil, topographically characterized as an area with escarpment of passive continental margin, where, close to the coast, the Serras do Mar and Serra da Mantiqueira stand out. The relief of the PSMV area and its respective drainage network had its evolution conditioned to the tectonic and climatic events that occurred during the Cenozoic. The oldest tectonic event is described as a NW-SE (E1) stretch, of Paleogenic age, followed by an E-W sinistral transcurrence (TS) event in the Neogene and a dextral transcurrence (DT) event, which occurred in the Pleistocene-Holocene. Finally, the extension event (E2) in the Holocene was associated with generalized reactivations of NE-SW structures, locally related to the generation of grabens, such as the Rio Bananal graben.Although of great importance in studies involving relief evolution, there are still few works that use river profiles and fluvial gradient indices such as &#967; and ksn to analyze the role of river captures in the reorganization of drainage networks and their relationship with neotectonics. Thus, the present study aims to investigate the causes of the reorganization of the drainage network in the MVPS region and its relationship with the evolution of the relief and its respective neotectonic activity. The E1 event was responsible for the consolidation of the hemi-graben configuration of the sedimentary basins in the MVPS. The normalized steepness index calculated for the main rivers demonstrates that this configuration possibly established a greater erosive power for the basins that drained the active fault, represented by the basins of the northern sector of the study area. During the Neogene, the TS event occurred, responsible for the inflections of the main channels to N-NW. These inflections are marked by knickpoints and sudden changes of &#967; and ksn in the fluvial profiles of the main channels. The paleotension analysis showed that structures associated with the TD event may be related to the filling and clogging of valleys with alluvium-colluvium ramps. The E2 event generated a system of normal transcurrent faults associated with a NW-SE Holocene extensional regime, responsible for captures oriented preferentially to SE and secondarily to NW. In the field, the relationship between TD and E2 was observed: the first related to NW-SE triangular facets and filling by valleys with alluvial-colluvium ramps and then, the fluvial capture promoted by E2. The Chi-z fluvial profiles and longitudinal profiles corroborate this model, indicating migration of the dividers compatible with the main capture directions observed.</p>
<p>Both internal and external Earth&#8217;s dynamics are constantly changing the landscapes and one of the most influent external components are the fluvial processes, altering the relief through erosion and fluvial deposition, as well as through its respective drainage network&#8217;s reorganization. The drainage basins dynamics seeks to achieve a balance between tectonic uplift and river erosion. The use of parameter <em>Chi</em> (&#967;) allows a comparison of basins in different scales, erosion and uplift rates, making it possible to determinate its steady or transient state and comprehends the dynamics de divisor migration of basins. Although the great advances have been reached in last decades, there are still many questions without answer. For the accomplishment of this study, two areas in the Serra do Mar of S&#227;o Paulo and Paran&#225; were chosen due to the presence of important river captures, which generated significant reorganizations in the drainage network. Furthermore, cosmogenic isotopes (<sup>10</sup>Be) data from existent literature in Serra do Mar of Paran&#225; allows the estimation of the denudation rate of these basins in the long term. In this study, these rates are analyzed combined with values of <em>Chi</em>, verifying the influence of the captured rivers, which contribute to the understanding of landscape evolution. This study uses the Digital Elevation Model (DEM) SRTM 30m. The DEM data were treated in ArcGIS and analyzed in MATLAB, where oceanic and continental basins were selected, considering sea level as the base level. The analysis was made through functions of <em>Topographic Analysis Kit</em> (TAK), integrated to <em>TopoToolBox</em>, to generate longitudinal and elevation-Chi profiles and <em>Chi</em> maps plotted with knickpoints data and, for the Paran&#225; basins, the product obtained were simultaneously analyzed with <sup>10</sup>Be data. From the analysis of these data, was possible to notice the ocean basins are capturing the continental basins and, therefore, that these basins are in a transient state, which means that their divisor is migrating towards higher Chi values, thus, towards the interior of the continent. In Paran&#225; basins, the retreating areas of the Serra do Mar escarpment directly related to places of high erosion rates on the oceanic slope. These results, although preliminary, attest the potential of analysis methods used, proving the influence of river captures in the disruption of the steady state between adjacent drainage basins located on the oceanic and continental slopes, as well as their influence on the differentiated retreat in the Serra do Mar escarpment.</p>
<p>In the last few decades, many studies have focused on the hydrologic effects and sediment regulation by LULC changes. Besides, land degradation by soil erosion is a major problem in many tropical developing countries, particularly when natural vegetation is converted to farmland. In Brazil, the MATOPIBA Region located in the Cerrado biome, has been considered the greatest national agricultural frontier, responsible for a large part of the Brazilian production of grains and fibers. The flat topography, the deep soils and the favorable climate for the cultivation of the main crops of grains favored the accelerated agricultural expansion in the last 30 years. In order to analyze and measure erosion and sediment regulation in the Rio Grande watershed were performed using two models: InVEST and ARIES. The aim of the InVEST model is to map and quantify the sediment delivery and retention services. It is a spatially-explicit model working with calculations at the pixel scale. The ARIES program works through ecosystem services modeling and calculations that, depending on the used module, considers both supply and demand. The mean sediment retention, in InVEST model, which is the difference in the amount of sediment delivered by the current watershed and a hypothetical watershed where all land use types have been converted to bare ground, was 42.76 ton/year/ha. These results should be taken as a good first estimate of the current scenario for the sediment retention service. This is due to some limitations of the SDR model. It uses the revised universal soil loss equation (RUSLE), which is limited in scope with regards to sediment source. ARIES model, for the Sediment Regulation analysis, used RUSLE to calculate soil loss and soil retention by vegetation in tons of sediments per hectare per year. The data of rain erosivity comes from the Global Rainfall Erosivity database (factor <em>R</em>) and the soil erodibility data (factor <em>K</em>) from Soil Grids. The sediment retention calculation is done through the application of RUSLE twice, first with the current land use and land cover and then with bare soil (Mart&#237;nez-L&#243;pez et al., 2019). Then a subtraction is made between the two outputs, which determines the collaboration that current use and coverage has on sediment retention. The basin presents a mean value of 905.37, standard deviation of 1854.58 and maximum and minimum value of 39982.67 and 0, respectively. A limitation of the InVEST sediment model compared and ARIES is the temporal and spatial scale of its outputs. It is able to provide only average annual impacts under steady state conditions, limiting the model&#8217;s usability for ecosystem services in need of assessment via timescales shorter than one year.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.