Uso do modelo HEC-RAS com base em informações de LiDAR para avaliação de inundações urbanas / Use of the HEC-RAS model based on LiDAR information for urban flood assessment

RESUMO O crescimento desordenado das cidades e o excesso de impermeabilização são problemáticas dos grandes centros urbanos, tendo como consequência principal a ocorrência de inundações e alagamentos. Nesse contexto, a modelagem hidrodinâmica pode ser uma importante ferramenta para a determinação de áreas inundáveis, permitindo estimar as cotas de inundação para diferentes cenários de tempos de retorno (TR) e chuvas de projetos, permitindo, assim, representar mais fielmente a realidade e minimizar erros decorrentes de projetos hidráulicos. Trabalhando em conjunto com o Sistema de Informações Geográficas (SIG), em que a geometria do canal é extraída por meio do Modelo Digital do Terreno (MDT) de alta precisão gerado por levantamento com técnica LiDAR (Light Detection and Ranging) e software de modelagem hidrodinâmica (Hydrologic Engineering Center — River Analysis System — HEC-RAS), foi possível avaliar diferentes cenários de inundações no trecho canalizado em concreto, no córrego Botafogo, em Goiânia, Goiás. Com os resultados da modelagem hidrodinâmica foi possível avaliar o comportamento da propagação das vazões geradas, constatando-se que para precipitações com TR de 50 anos ou mais, os limites da canalização não suportam os volumes gerados e transportados, provocando inundações em seis trechos críticos. Os dados obtidos pelo HEC-RAS puderam ser validados a partir de registros fotográficos divulgados pela imprensa local e levantamento topográfico dos locais inundados, de modo que a integração entre o SIG e a modelagem hidrodinâmica se mostrou eficiente para o estudo de áreas inundáveis.

ABSTRACT The disordered growth of cities and the excessive waterproofing are problematic of the large urban centers, having as a main consequence the occurrence of floods and overflows. Within this context, hydrodynamic modeling can be an important tool for the determination of floodable areas, allowing the estimation of flood quotas for different scenarios of return periods (TR) and project rainfall, thus allowing to more accurately represent reality and minimize errors arising from hydraulic designs. Working with Geographic Information System (GIS), where the channel geometry is extracted using the high precision Digital Terrain Model (DTM) generated by LiDAR (Light Detection and Ranging) survey and hydrodynamic modeling software (HEC-RAS), it was possible to evaluate different flood scenarios in the channeled concrete section, in the Botafogo Stream in Goiânia, Goiás. With the results of hydrodynamic modeling, it was possible to evaluate the propagation behavior of the generated flows, finding that for precipitation with TR 50 years or older, the plumbing limits do not support the generated and transported volumes, causing flooding in six critical stretches. The data obtained by HEC-RAS could be validated from photographic records released by the press and topographic survey of flooded sites, so that the integration between GIS and hydrodynamic modeling proved to be efficient for the study of floodable areas.

Use of a geographic information system to find areas for locating of municipal solid waste management facilities.

Municipal solid waste (MSW) management is a pressing concern for Goiás State, Brazil. Of the state's 246 municipalities, only 16 send their waste to licensed landfills. This means that 93% of the cities in Goiás dispose of their MSW inappropriately, in dumps or unlicensed landfills. This practice poses a danger to both the environment and to public health. On this basis, the goal of this study was to survey potential landfill sites in Goiás. A geographic information system tool was used to first identify Goiás landfills and dumps and then examine them, to check whether they are located in legally restricted areas. This tool cross-references morphology, land use and occupancy, conservation of the environment, public health and population projections for 2040. It then outputs restriction-free areas that are suitable for landfill construction. The results indicate that, by 2040, Goiás will have 59,500 km2 available for landfills, i.e., 17% of the state's total area. Conversely, 60% of the state's geographical area will be off limits for landfill construction. The most urgent need is in the Goiânia Metropolitan area, which will be producing about 40%, of 6,850 t⋅day-1, of the MSW generated in the state by 2040. This metropolitan area will have the smallest restriction-free area for landfill construction (832 km2). A total of 235 MSW final disposal facilities were identified in Goiás: 15 licensed landfills, 23 unlicensed landfills and 197 dumps. Of these, 15 are in permitted areas, 38 are in areas subject to approval and 182 are in restricted areas. These numbers highlight the need for Goiás municipalities to terminate and/or readjust landfills and unlicensed dumps and to set up new MSW management facilities that conform to the legal and environmental requirements and the expected population growth.