Modelagem das transformações no uso da terra, de processos erosivos e de escoamento superficial na bacia hidrográfica do Ribeirão São Domingos, município de Santa Cruz do Rio Pardo - SP
Carregando...
Data
2019-06-14
Autores
Demarchi, Julio Cesar [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
No processo de produção do espaço geográfico, o homem promove mudanças no uso da terra e, consequentemente, alterações no ciclo hidrológico, que dão origem a impactos ambientais negativos, tais como o aumento das taxas de erosão do solo, da exportação de sedimentos das bacias hidrográficas e do escoamento superficial, principalmente quando reduz ou elimina a cobertura vegetal. Tais impactos são observados na bacia do Ribeirão São Domingos, localizada no município de Santa Cruz do Rio Pardo – SP, que passou pelos processos de expansão urbana e intensificação da ocupação agrícola a partir da década de 1970. Nesse contexto, o objetivo desta tese foi analisar a influência das transformações ocorridas no uso da terra da referida bacia hidrográfica desde a década de 1960 e em cenários futuros de uso na configuração dos processos de erosão, aporte de sedimentos e escoamento superficial, por meio de modelagem, como subsídio ao ordenamento territorial urbano e rural. Para tanto, foi necessário: caracterizar os usos da terra passados e atuais; simular os cenários futuros; levantar, caracterizar e mapear os solos da área de estudo; ajustar a equação Intensidade-Duração-Frequência (IDF) para utilização nos estudos hidrológicos; realizar as modelagens de erosão e hidrológica; analisar os instrumentos de ordenamento territorial e parcelamento do solo do Plano Diretor do município e propor as alterações necessárias à redução do escoamento superficial e do perigo de inundação na bacia. A metodologia baseou-se na elaboração dos mapas de uso da terra dos anos 1962, 1984, 2004, 2018 e de adequação à legislação florestal vigente, no levantamento semidetalhado de solos e na coleta de dados pluviométricos, fluviométricos e sedimentométricos, que constituíram a base para as modelagens. As alocações espaciais dos cenários futuros de uso da terra foram simuladas pelo modelo Dyna-CLUE. A modelagem de erosão e aporte de sedimentos no exutório da bacia hidrográfica foi realizada no modelo WaTEM/SEDEM, e a modelagem hidrológica foi conduzida no programa HEC-HMS, pelo método do Número da Curva do Serviço de Conservação do Solo dos Estados Unidos. A série histórica de mapas de uso da terra possibilitou a compreensão do processo de modernização da agricultura ocorrido a partir da década de 1970, o declínio da lavoura cafeeira e sua substituição pelas pastagens e culturas agrícolas destinadas à agroindústria ou à exportação, além do crescimento urbano. Os cenários futuros 1 a 4 mostraram a alocação espacial do crescimento urbano, industrial e da área cultivada pelas commodities agrícolas em diferentes intensidades, ao passo que os cenários 5 e 6 representaram as especializações produtivas na produção florestal e na criação de gado, respectivamente. A modelagem de erosão apontou a redução em suas taxas e nas de exportação de sedimentos pela bacia de 1962 a 2018, e a redução ainda maior nos cenários 5, 6 e de adequação à Legislação Florestal (LF) comparada ao ano-base 2018, devido à evolução dos sistemas de cultivo e à adoção de práticas de conservação do solo. O aumento dessas taxas nos cenários 1 a 4 está associado ao crescimento das áreas agrícolas e/ou urbanas em detrimento das pastagens. A modelagem hidrológica evidenciou o aumento do escoamento superficial no período de 1962 a 2018 e nos cenários futuros 1 a 4, e sua redução nos cenários 5, 6, LF e drenagem urbana moderna. Por fim, verificou-se que os parâmetros urbanísticos Taxa de Ocupação e Taxa de Permeabilidade, associados às macrozonas rurais estabelecidas no Plano Diretor do município, possibilitam a expansão urbana e o parcelamento do solo para uso por chácaras de recreio no perímetro da bacia hidrográfica e o consequente aumento da intensidade dos episódios de inundação, o que foi comprovado pelas simulações hidrológicas realizadas nessas condições. Diante deste fato, foi elaborada uma proposta alternativa de macrozoneamento e das diretrizes de uso da terra para o município, para controlar o escoamento superficial na área de estudo.
In the process of producing the geographical space, humans promote changes in land use and, consequently, changes in the hydrological cycle, which generate negative environmental impacts such as an increase in soil erosion rates, sediment yield and surface runoff at the watershed outlets, especially when the vegetal cover is reduced or eliminated. These impacts are observed in São Domingos stream watershed, located in the municipality of Santa Cruz do Rio Pardo, in São Paulo state, which has undergone urban expansion and intensification of agricultural use since the 1970s. In this context, this thesis aims to analyze the influence of land use changes in this watershed, since the 1960s and in future use scenarios, in the configuration of erosion processes, sediment yield, and surface runoff by means of modeling, as a subsidy to the urban and rural land use planning. Aiming this objective, the following steps were necessary: to characterize the past and current land uses; to simulate future scenarios; to survey, characterize and map the soils of the study site; to adjust the Intensity-Duration-Frequency (IDF) equation to be used in hydrological studies; to perform erosion and hydrologic modeling; to analyze the land use planning and soil parceling instruments of the municipality’s master plan and to propose the necessary changes in order to reduce runoff and flood hazard in the watershed. The methodology was based on the production of land use maps for the years 1962, 1984, 2004, 2018 and land use adequacy to current forest laws, on semi-detailed soil survey, and the collection of rainfall, discharge, and sedimentometric data, which served as the basis for the modeling. The spatial allocations of future land use scenarios were simulated by the Dyna-CLUE model. The modeling of erosion and sediment yield at the basin outlet was performed based on the WaTEM/SEDEM model, and the hydrological modeling was carried out in the HEC-HMS program, using the US Soil Conservation Service Curve Number method. The time series of land use maps made it possible to understand the agriculture modernization process that started in the 1970s, the decline of coffee plantations, their replacement by pastures and farm crops dedicated to agroindustry or exportation, besides urban growth. Future scenarios 1 to 4 showed the spatial allocation of urban and industrial growth, as well as the increase of commodities cultivated fields in different intensities, whereas scenarios 5 and 6 represented productive specializations in forest production and cattle breeding, respectively. The erosion modeling showed a reduction in soil loss and sediment yield at the watershed outlet from 1962 to 2018, and an even greater reduction in the scenarios 5 and 6, and in an adequacy to Forest Laws (FL) if compared to the base year 2018, due to crop systems evolution and the adoption of soil conservation techniques. The increase of these rates in scenarios 1 to 4 is associated with the growth of farmlands and urban areas over pastures. The hydrological modeling demonstrated the runoff increase from 1962 to 2018 and in the future scenarios 1 to 4, and its reduction in 5, 6, FL, and modern urban drainage scenarios. Finally, it has been verified that the urbanistic coefficients of Occupancy Rate and Permeability Rate, associated with the rural zoning established by the municipality’s master plan, have allowed an urbanization increase and land parceling for recreational farms on the watershed perimeter, and they have increased the intensity of flood events, which was confirmed by the hydrological simulations that reproduced those conditions. Given this fact, an alternative municipality zoning and land use guidelines proposal was developed in order to control surface runoff on the study site.
In the process of producing the geographical space, humans promote changes in land use and, consequently, changes in the hydrological cycle, which generate negative environmental impacts such as an increase in soil erosion rates, sediment yield and surface runoff at the watershed outlets, especially when the vegetal cover is reduced or eliminated. These impacts are observed in São Domingos stream watershed, located in the municipality of Santa Cruz do Rio Pardo, in São Paulo state, which has undergone urban expansion and intensification of agricultural use since the 1970s. In this context, this thesis aims to analyze the influence of land use changes in this watershed, since the 1960s and in future use scenarios, in the configuration of erosion processes, sediment yield, and surface runoff by means of modeling, as a subsidy to the urban and rural land use planning. Aiming this objective, the following steps were necessary: to characterize the past and current land uses; to simulate future scenarios; to survey, characterize and map the soils of the study site; to adjust the Intensity-Duration-Frequency (IDF) equation to be used in hydrological studies; to perform erosion and hydrologic modeling; to analyze the land use planning and soil parceling instruments of the municipality’s master plan and to propose the necessary changes in order to reduce runoff and flood hazard in the watershed. The methodology was based on the production of land use maps for the years 1962, 1984, 2004, 2018 and land use adequacy to current forest laws, on semi-detailed soil survey, and the collection of rainfall, discharge, and sedimentometric data, which served as the basis for the modeling. The spatial allocations of future land use scenarios were simulated by the Dyna-CLUE model. The modeling of erosion and sediment yield at the basin outlet was performed based on the WaTEM/SEDEM model, and the hydrological modeling was carried out in the HEC-HMS program, using the US Soil Conservation Service Curve Number method. The time series of land use maps made it possible to understand the agriculture modernization process that started in the 1970s, the decline of coffee plantations, their replacement by pastures and farm crops dedicated to agroindustry or exportation, besides urban growth. Future scenarios 1 to 4 showed the spatial allocation of urban and industrial growth, as well as the increase of commodities cultivated fields in different intensities, whereas scenarios 5 and 6 represented productive specializations in forest production and cattle breeding, respectively. The erosion modeling showed a reduction in soil loss and sediment yield at the watershed outlet from 1962 to 2018, and an even greater reduction in the scenarios 5 and 6, and in an adequacy to Forest Laws (FL) if compared to the base year 2018, due to crop systems evolution and the adoption of soil conservation techniques. The increase of these rates in scenarios 1 to 4 is associated with the growth of farmlands and urban areas over pastures. The hydrological modeling demonstrated the runoff increase from 1962 to 2018 and in the future scenarios 1 to 4, and its reduction in 5, 6, FL, and modern urban drainage scenarios. Finally, it has been verified that the urbanistic coefficients of Occupancy Rate and Permeability Rate, associated with the rural zoning established by the municipality’s master plan, have allowed an urbanization increase and land parceling for recreational farms on the watershed perimeter, and they have increased the intensity of flood events, which was confirmed by the hydrological simulations that reproduced those conditions. Given this fact, an alternative municipality zoning and land use guidelines proposal was developed in order to control surface runoff on the study site.
Descrição
Palavras-chave
Modelagem ambiental, Ordenamento territorial, Mudança no uso da terra, Produção do espaço geográfico, Gestão de bacias hidrográficas, Environmental modeling, Land use planning, Land use change, Production of geographic space, Watershed management