Zoneamento do escoamento superficial da bacia hidrográfica do Rio Paciência, Ilha do Maranhão-MA
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Data
2016-01-08
Autores
Cavalcanti Júnior, Francisco Afonso [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A proposta deste estudo foi a elaboração da carta do potencial de escoamento superficial da bacia hidrográfica do Rio Paciência – MA. Essa bacia hidrográfica apresenta uma área de 150 km² e está inserida nos quatro municípios da Região Metropolitana da Grande São Luís, na Ilha do Maranhão: São Luís, São José de Ribamar, Paço do Lumiar e Raposa. Os trabalhos de campo foram realizados em parceria com o Laboratório de Estudos de Bacias Hidrográficas – LEBAC da Universidade Federal do Maranhão. Na elaboração da carta de escoamento superficial foi empregada a Técnica de Cartografia Geotécnica conforme Zuquette (1993) e Zuquette e Gandolfi (2004), na qual se buscou avaliar e caracterizar as variáveis do meio físico associadas aos diferentes usos da terra. Nessa técnica as características geotécnicas relacionadas à geologia, tipos de solos (textura, morfologia e permeabilidade), densidade de drenagem, declividade e feições favoráveis ao armazenamento superficial, são agrupadas em classes e atribuídos valores específicos. O produto final foi o resultado do cruzamento dos atributos dos meios físico e antrópico através do uso de aplicativos em ambiente de Sistema de Informações de Geográficas. A partir da análise dos resultados concluiu-se que os problemas identificados são consequência, antes de tudo, da má administração dos gestores públicos evidenciado nas ruas não pavimentadas e ausência de calçamento das marginais das vias de transporte, abrangência e manutenção do sistema de esgoto quando existente, urbanização não planejada, concessão de área para a construção de empreendimentos imobiliários desconsiderando a legislação ambiental e as aptidões físicas do terreno. Os problemas resultantes, como os alagamentos, afetam tanto os moradores da bacia hidrográfica quanto uma parcela da população da Ilha que por ela transita. Não foram encontrados registros de mortes causadas pelos alagamentos e, de modo geral, as consequências incorrem quase sempre em transtornos no fluxo dos transportes, no comércio de porte pequeno e em perdas materiais. Foram estabelecidas cinco classes de potenciais de escoamento: muito alto, alto, médio, baixo e muito baixo. Em 35% da área da bacia, o alto potencial ao escoamento superficial foi predominante, principalmente no alto curso, onde se encontram os maiores adensamentos urbanos, sendo este o parâmetro de maior peso para o fenômeno observado e não a declividade. Conforme pode ser observado na carta de escoamento superficial e na sua análise, a bacia hidrográfica apresentou um cenário muito favorável ao escoamento superficial, com 58% do seu território variando de potencial muito alto a potencial médio. Tal faixa equivale ao alto e médio curso da bacia que se caracterizam por serem áreas mais urbanizadas. Do lado oposto, o baixo curso e as margens dos interflúvios representam 42% do território bacia variando de potencial baixo a potencial muito baixo. As áreas de potencial muito baixo, correspondendo aos topos de tabuleiros e colinas no baixo curso da bacia hidrográfica, são áreas com solo predominantemente arenoso, vegetadas e pouco urbanizadas. No zoneamento, a preservação dessas áreas é importante não somente para evitar problemas decorrentes do escoamento superficial, mas também para a segurança hídrica da bacia. A hipótese central da pesquisa foi confirmada, porém se faz necessário a realização deste mesmo estudo em outras bacias vizinhas ou até mesmo em toda a Ilha do Maranhão para que se tenham parâmetros, e assim se possa melhor dimensionar os impactos do escoamento superficial. Essas informações podem auxiliar no planejamento ambiental do uso e cobertura da terra da referida bacia hidrográfica, sendo um importante documento para futuros projetos de ordenamento do espaço geográfico.
The purpose of this study was the development of the potential runoff map from the Paciência River Basin. This basin covers an area of 150 km² and is embedded in the four municipalities of the Metropolitan Region of Greater São Luis at Ilha do Maranhão: São Luís, São José de Ribamar, Paço do Lumiar and Raposa. The fieldwork was carried out in partnership with the Basin Research Laboratory Hydrographic - LEBAC from Federal University of Maranhão. In preparing the runoff map it was employed the Geotechnical Mapping Technique as Zuquette (1993) and Zuquette and Gandolfi (2004), which aimed to evaluate and characterize the variables of the physical environment associated with different land uses. In this technique the geotechnical characteristics related to geology, soils (texture, morphology and permeability), drainage density, slope and features favorable to surface storage, are grouped into classes and specific value are assigned. The final product was the result of physical and man-made resources attributes crossing through the software of use in Geographic Information System environment. From the analysis of the results it was concluded that the identified problems are consequence, first of all, of poor management of public managers evidenced in the unpaved streets and absence of sidewalks in the marginal transportation routes, coverage and maintenance of the sewer system, when present, unplanned urbanization, concession area for the construction of real estate projects without considering the environmental legislation and the physical parameters of the land. The resulting problems such as flooding, affect both the residents of the basin and a portion of the island population during its movement. There were no records of deaths caused by flooding and the consequences generally incur in disturbances in the transport flow, in small trade and material losses. Five runoff potential classes were established: very high, high, medium, low and very low. In a 35% of the basin area, the high potential to runoff was predominant, especially in the upper reaches, where are the largest urban concentrations, which is the main parameter to the observed phenomenon and not the slope. As can be seen in the runoff map and its analysis, the basin had a very favorable runoff scenario, with a 58% of its territory ranging from very high to medium potential. Such range is equivalent of the high and medium-haul basin that are characterized by being more urbanized areas. In the opposite side, the lower course and the interfluve banks represent a 42% of the basin territory ranging from low to very low potential. The very low potential areas, corresponding to the tops of hills and trays in the lower course of the river basin, are areas with predominant sandy soil, vegetated and poorly urbanized. Zoning, in the preservation of these areas, is important not only to avoid the problems resulting from runoff, but also to the water security of the basin. The central hypothesis of the research was confirmed, but it is necessary the realization of similar study in other neighboring basins or even across the Ilha do Maranhão in order to obtain parameters and thus better scale of the runoff impacts. This information can assist in planning the environmental use and cover of the land from this basin, being an important document for future geographic spatial planning projects.
The purpose of this study was the development of the potential runoff map from the Paciência River Basin. This basin covers an area of 150 km² and is embedded in the four municipalities of the Metropolitan Region of Greater São Luis at Ilha do Maranhão: São Luís, São José de Ribamar, Paço do Lumiar and Raposa. The fieldwork was carried out in partnership with the Basin Research Laboratory Hydrographic - LEBAC from Federal University of Maranhão. In preparing the runoff map it was employed the Geotechnical Mapping Technique as Zuquette (1993) and Zuquette and Gandolfi (2004), which aimed to evaluate and characterize the variables of the physical environment associated with different land uses. In this technique the geotechnical characteristics related to geology, soils (texture, morphology and permeability), drainage density, slope and features favorable to surface storage, are grouped into classes and specific value are assigned. The final product was the result of physical and man-made resources attributes crossing through the software of use in Geographic Information System environment. From the analysis of the results it was concluded that the identified problems are consequence, first of all, of poor management of public managers evidenced in the unpaved streets and absence of sidewalks in the marginal transportation routes, coverage and maintenance of the sewer system, when present, unplanned urbanization, concession area for the construction of real estate projects without considering the environmental legislation and the physical parameters of the land. The resulting problems such as flooding, affect both the residents of the basin and a portion of the island population during its movement. There were no records of deaths caused by flooding and the consequences generally incur in disturbances in the transport flow, in small trade and material losses. Five runoff potential classes were established: very high, high, medium, low and very low. In a 35% of the basin area, the high potential to runoff was predominant, especially in the upper reaches, where are the largest urban concentrations, which is the main parameter to the observed phenomenon and not the slope. As can be seen in the runoff map and its analysis, the basin had a very favorable runoff scenario, with a 58% of its territory ranging from very high to medium potential. Such range is equivalent of the high and medium-haul basin that are characterized by being more urbanized areas. In the opposite side, the lower course and the interfluve banks represent a 42% of the basin territory ranging from low to very low potential. The very low potential areas, corresponding to the tops of hills and trays in the lower course of the river basin, are areas with predominant sandy soil, vegetated and poorly urbanized. Zoning, in the preservation of these areas, is important not only to avoid the problems resulting from runoff, but also to the water security of the basin. The central hypothesis of the research was confirmed, but it is necessary the realization of similar study in other neighboring basins or even across the Ilha do Maranhão in order to obtain parameters and thus better scale of the runoff impacts. This information can assist in planning the environmental use and cover of the land from this basin, being an important document for future geographic spatial planning projects.
Descrição
Palavras-chave
Escoamento superficial, Mapeamento geoambiental, Permeabilidade do solo, Runoff, Geoenvironmental mapping, Soil permeability