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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Sistemas de dunas do Parque das Dunas e Barreira do Inferno/Natal (RN): levantamento geol?gico /geof?sico, elabora??o do modelo determin?stico e avalia??o da vulnerabilidade/suscetibilidade frente ?s press?es antr?picas.

Fracasso, Paola 30 June 2005 (has links)
Made available in DSpace on 2015-03-13T17:08:24Z (GMT). No. of bitstreams: 1 PaolaF_ate_Cap4.pdf: 1280968 bytes, checksum: 66cf6acbdf671531fe325f80fb3ce840 (MD5) Previous issue date: 2005-06-30 / The current work was developed on the dune systems of the Parque das Dunas and Barreira do Inferno. These places are located in the cities of Natal and Parnamirim (RN, Brazil), respectively. This project has the purpose of developing the deterministic model on a specific blowout at Parque das Dunas, based in the geophysical interpretations of the lines gotten with the Ground Penetration Radar and the planialtimetric acquisitions of the topographical surface of the land. Also analyses of the vulnerability/susceptibility of these dune systems had been done in relation to the human pressures. To develop its deterministic model, it is necessary to acquire inner and outer geometries of the cited blowout. In order to depict inner geometries underneath the surface are used the GPR observing the altimetric control for topographical correction of the GPR lines. As for the outer geometries, the geodesic GPS gives us the planialtimetric points (x, y and z points) with milimetric precision, resulting in high-resolution surfaces. Using interpolation methods of the planialtimetric points was possible create Digital Elevations Models (DEM?s) of these surfaces. As a result, 1,161.4 meters of GPR lines were acquired on the blowout at the Parque das Dunas and 3,735.27 meters on the blowout at the Barreira do Inferno. These lines had been acquired with a 200 MHz antenna, except the 7 and 8 lines, for which we had been used a 100 MHz antenna. The gotten data had been processed and interpreted, being possible to identify boundary surfaces of first, second and third order. The first order boundary surface is related with the contact of the rocks of the Barreiras Group with the aeolian deposits. These deposits had been divided in two groups (Group 1 and Group 2) which are related with the geometry of stratum and the dip of its stratifications. Group 1 presented stratum of sigmoidal and irregular geometries and involved bodies where the reflectors had presented dips that had varied of 20 to the 28 degrees for the Parque das Dunas blowout and of 22 to the 29 degrees for the Barreira do Inferno blowout. Usually, it was limited in the base for the first order surface and in the top for the second order surface. Group 2 presented stratum of trough, wedge or lens geometries, limited in the base for the second order vi surface, where the corresponding deposits had more shown smoothed reflectors or with dips of low angle. The Deterministic and Digital Elevation Models had been developed from the integration and interpretation of the 2D data with the GOCAD? program. In Digital Elevations Models it was possible to see, for the localities, corridor or trough-shaped blowouts. In Deterministic Model it was possible to see first and second order boundary surfaces. For the vulnerability/susceptibility of the dune systems it was applied the methodology proposal by Boder? al (1991); however the same one did not show adequate because it evaluates actual coastal dunes. Actual coastal dunes are dunes that are presented in balance with the current environmental conditions. Therefore, a new methodology was proposal which characterizes the supplying and activity sedimentary, as well as the human pressures. For the methodology developed in this work, both the localities had presented a good management. The Parque das Dunas was characterized as a relic dune system and the Barreira do Inferno was characterized as a palimpsestic dune system. Also two Thematic Maps had been elaborated for the environmental characterization of the studied dune systems, with software ArcGis 8.3, and its respective data bases / O presente trabalho foi realizado no Sistema de Dunas do Parque das Dunas e Barreira do Inferno, localizados, respectivamente, nos munic?pios de Natal e Parnamirim, estado do Rio Grande do Norte. O objetivo deste trabalho foi elaborar um modelo determin?stico em uma fei??o erosional, denominada de ruptura de defla??o, localizada no Parque das Dunas, com base nas interpreta??es geof?sicas das linhas obtidas com o GPR (Radar de Penetra??o no Solo) e do levantamento plani-altim?trico da superf?cie topogr?fica do terreno. Foram tamb?m realizadas an?lises da vulnerabilidade/suscetibilidade destes sistemas dunares frente ?s press?es antr?picas. Para a elabora??o do modelo foi necess?rio ? aquisi??o das geometrias internas e externas da ruptura de defla??o. As geometrias internas foram obtidas com o GPR, observando-se o controle altim?trico para corre??o topogr?fica dos radargramas ou linhas de GPR. As superf?cies externas foram adquiridas a partir dos levantamentos planialtim?tricos de precis?o com o GPS Geod?sico. Estas superf?cies foram superpostas a imagens Ikonos para gera??o do Modelo Digital de Terreno (MDT) de alta precis?o. Foram levantadas, no total, dezesseis linhas de GPR, sendo oito para cada localidade o que totalizou 1.161,4 metros para a ruptura de defla??o do Parque das Dunas e 3.735,27 metros para a ruptura da Barreira do Inferno. Os levantamentos foram realizados com a antena de 200 MHz, com exce??o das linhas 7 e 8 da Barreira do Inferno, para as quais foram utilizadas antenas de 100 MHz. Os dados obtidos foram processados e interpretados, sendo poss?vel identificar superf?cies limitantes de primeira, segunda e terceira ordem. A superf?cie limitante de primeira ordem est? relacionada com o contato das rochas do Grupo Barreiras com os dep?sitos e?licos. Esses dep?sitos foram divididos em dois grupos (Grupo 1 e Grupo 2) os quais est?o relacionados com a geometria dos estratos e do mergulho das suas estratifica??es (?ngulo dos refletores). O Grupo 1 apresentou estratos de geometria sigmoidal e irregular e envolveu corpos onde os refletores apresentaram mergulhos que variaram de 20 ? 28 graus para a ruptura de defla??o no Parque das Dunas e de 22 ? 29 graus para a ruptura de defla??o na Barreira do Inferno. Frequentemente estava limitado na base pela superf?cie de primeira ordem e no topo pela superf?cie de segunda ordem. O Grupo 2 apresentou estratos de geometrias acanaladas, em cunha ou lenticular, limitado naiv base pela superf?cie de segunda ordem, onde os dep?sitos correspondentes mostraram refletores mais aplainados ou com mergulho de baixo ?ngulo. Os Modelos Determin?stico e Digital de Terreno (MDT) foram gerados a partir da integra??o e interpreta??o dos dados 2D disponibilizados espacialmente com o software GoCad 2.0.8 ?. No MDT foi poss?vel identificar, para ambas as localidades, rupturas de defla??o do tipo corredor e no Modelo Determin?stico foi poss?vel evidenciar as superf?cies limitantes de primeira e segunda ordem. Em rela??o ? vulnerabilidade/suscetibilidade do sistema de dunas frente as press?es antr?picas, foi aplicada a metodologia proposta por Boder? et al (1991), no entanto, a mesma n?o mostrou-se adequada, pois avalia dunas costeiras atuais, ou seja, dunas que apresentam-se em equil?brio com as condi??es ambientais atuais. Assim, foi proposta uma nova metodologia a qual caracteriza, alem das press?es antr?picas, o abastecimento e atividade sedimentar. Para a metodologia desenvolvida neste trabalho, ambas as localidades enquadraram-se dentro do est?gio de equil?brio frente ?s press?es antr?picas, sendo o Parque das Dunas caracterizado como um campo dunar rel?quia e a Barreira do Inferno, como um campo dunar palimpsestico. Foram tamb?m confeccionados para a caracteriza??o ambiental dos sistemas de dunas estudados dois Mapas Tem?ticos, com o software ArcGis 8.3., e seus respectivos bancos de dados

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