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Navegando por Assunto "Erosão"

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    Análise integrada da paisagem e processos de erosão costeira na ilha de Atalaia, Salinópolis, Pará
    (Universidade Federal do Pará, 2024-03-27) SOUZA, Ewerton Müller da Silva; ANDRADE, Milena Marília Nogueira de; http://lattes.cnpq.br/1930321094483005; https://orcid.org/0000-0001-5799-7321
    The study aims to analyze the landscape and erosion susceptibility processes on Atalaia Island, Salinópolis, Pará, as a basis for coastal management policies. The objective unfolds in examining the coastline position between 2002 and 2022, identifying coastal dynamics through geoindicators, analyzing landscape units, and the degree of susceptibility to erosion on the island. To achieve the objectives, the study area was divided into three sectors: Espadarte, Atalaia, and Sofia. The materials and methods used include satellite images for a twenty-year multi-temporal analysis, with polygon change analysis techniques, areal and linear rates. For this assessment of coastal changes, the Digital Shoreline Analysis System (DSAS) plugin was used in the Geographic Information System environment of ArcMap 10.5. The use of geoindicators was granted through field sheets with the identification of natural or anthropogenic elements that pointed to the movement of the coastline. For the landscape analysis, the theoretical basis of landscape geoecology and the use of geoprocessing to generate a map of landscape units were used. The study revealed areas of high susceptibility with 47,798m², mainly in sector A, in this sector, geoindicators such as the front strip of vegetation modified by erosion (44) and the presence of retaining walls and other constructions in contact with the beach arch or on the surface of estirance (64) stand out. The areas of moderate susceptibility were present, prominently in Sector B, with an area of 66,950m², in this sector, the geoindicators of water/sewage piping or energy poles, located on the beach arch in a situation of destruction by physical agents (54) and the presence of retaining walls and other constructions in contact with the beach arch or on the surface of estirance (62) stand out. The areas of low susceptibility to erosion were present, most evidently, in Sector C, with an area of 341,274.1m², in this sector, the geoindicator related to the width of the post-beach/sandy berm surface (70) stands out. The results of the landscape analysis allowed the understanding of the structure and functioning of the fluvio-marine plain, urban areas, open areas, moving dunes, and beach and post-beach. The investigation offers a dynamic perspective on the erosion processes of Atalaia Island from the employed methodology, thereby, the results indicate the need for more effective coastal management strategies, underlining the importance of an integrated approach that considers both physical and socioeconomic aspects to mitigate adverse impacts on local communities and the ecosystem.
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    Análise multitemporal (1991-2021) da linha de costa (trecho Calçoene - Cabo Norte), costa atlântica do estado do Amapá.
    (Universidade Federal do Pará, 2023-08-21) SILVA, Rhuan Rodrigo Pereira e; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; https://orcid.org/0000-0001-7850-1217
    The coastline (LC) is highly dynamic due to its geographic position adjacent to the mouth of the Amazon River estuary. This region is characterized by meteorological forcings, such as a semihumid equatorial climate, high rainfall (> 2,600 mm. year-1), winds (3 to 9 m. s-1), and extreme events (El Nino - 1997/1998 and 2015/2016; La Nina - 1999/2000 and 2010/2011). It is also influenced by hydrological forcings, including water and solid discharge from the Amazon River (175,000 m³ s-1 and 1,200 Mt. year-1, respectively), and oceanographic forcings, such as hyper-tides (up to 12 m), tidal currents (2 m. s-1), waves (up to 3 m in height), and currents (up to 3 m. s-1). This study aims to analyze the multitemporal variation of the LC between the mouths of the Calçoene and Sucuriju rivers, and at the Maracá-Jipioca Ecological Station, from 1991 to 2021. The methodology includes a literature review, acquisition of LANDSAT satellite images (1991, 2000, 2008, 2014, and 2021), LC vectorization, and the application of DSAS to quantify accretion (m) and erosion areas (m) of the LC, determine retreat and advance rates (m/year and m²/year) between the mouths of the Calçoene and Sucuriju rivers, and create change polygons at the Maracá-Jipioca Ecological Station. The study area experienced predominant erosive dynamics, with an average LC retreat of 12 m. year-1 and 1.4 km² of erosion in the Calçoene-Sucuriju stretch, and 2 km² of erosion at the Maracá-Jipioca Ecological Station with an annual average retreat of approximately 18 m. Due to erosive dynamics, the study area requires special attention from public managers to prevent any type of anthropic interference that could intensify this process.
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    Estudo geofísico sobre a erosão fluvial do Rio Guamá na orla da Universidade Federal do Pará, Belém (PA)
    (Universidade Federal do Pará, 2011-09-27) DIAS, Gustavo Nogueira; SILVA, Lúcia Maria da Costa e; http://lattes.cnpq.br/8612431024609774
    The present work is a geophysical study of a riverbank exposed to erosion and it aims to evaluate its use for detecting areas degraded by critical erosion stage before they collapse. The studied area is situated 600m alongside Guamá River – between Tucunduba River Bridge and Canoeing Pier at Federal University of Pará. The area has different kinds of erosion contentions along its way such as cement walls and cement bags. Therefore the place is considered a laboratory to test geophysics expertise in detecting areas affected by imperceptible process so that it can act before they erode. The following four geophysical methods were used: spontaneous potential –SP; electroresistivity; Slingram – LIN and ground penetration radar – GPR. The measures were taken during both low and high tides in order to map the preferable subsuperficial paths the water runs through. In general, tides increase oscillations in SP measures, electroresistivity and LIN as well as increase the reflections intensity from GPR compared to low tide measures and during high tide, measures show compared to low tide: I) In erosion affected area there is a voltage decrease in SP, a resistivity decrease in electroresistivity, a conductive increase in LIN as well as an intensity increase of the reflections and a continuity disturbance in GPR. II) In contained areas there is an increase of the SP voltage, an increase of the resistivity from electroresistivity, a decrease of the LIN conductivity and an ease in the reflections from the GPR and a reduction of tides global effects. Despite the difficulties, the results show Geophysics can be a useful tool not only on preventing affected areas from collapsing but also on analyzing the effectiveness of previous contention woks.
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    Modelagem numérica-experimental da produção de sedimentos de pequenas bacias hidrográficas da Amazônia
    (Universidade Federal do Pará, 2021-04-22) BARBOSA, Ana Júlia Soares da Silva; BLANCO, Claudio José Cavalcante; http://lattes.cnpq.br/8319326553139808; https://orcid.org/0000-0001-8022-2647
    Erosion is a process of direct impact in urban and rural environments. The understanding of this process requires the use of models and techniques of geoprocessing and field, for approximate estimation of the realized one, since it is a phenomenon with many variables to be taken into account. For the present study, two models were used to generate data in a small Amazon basin. The USLE (universal soil loss equation) and also the modified MUSLE version. For both models, the common factors (K, LS, C and P) were determined. For USLE, the calibration occurred for rain erosivity, which is the differential factor of this model. After USLE application with calibrated R factor, the model was applied to the study area with an average soil loss of 1.99 ton. ha-1.year-1, for a period of 21 years. For MUSLE, the differential variables are the hydrological variables (Q and qp) were determined by analyzing the hydrographs observed with the aid of a digital filter. Two methods of calibration and validation have been done for MUSLE. Method 1 calibrated the factors ɑ and b, with sediment production data measured from 62 flood events from 2012 to 2014. The values found for factors ɑ and b were equal to 19.90 and 0.60, respectively. MUSLE was validated with sediment production data measured from 62 flood events in the years 2014 and 2015. The validated MUSLE equation represented in a satisfactory way, in more than 70%, the data of soil loss observed in the hydrographic basin of the Igarapé da Prata. Method 2 calibrated only the value of a, using the solid discharge curve with potential regression for the years 2012 and 2013, which showed R² of 0.70 and 0.68, respectively. The value of ɑ obtained was 17.25, and was applied to MUSLE, keeping the value of b at 0.56, the original value of the model. The validation for the latter method proved to be adequate, with an R² of 0.69. These results validate the empirical models for the region with experimental activities, which corroborates for the production of sediment information in the Amazon region, as a way of maturing and the search for new research, for the understanding of the impacts arising from the transport of soil between areas and in the water environment.
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