Drenagem urbana: estudo dos impactos da expansão urbana do município de Medianeira-PR na vazão de cheia da bacia do rio Alegria a montante da foz do rio Bolinha

Abstract

Urban densification and consequent soil impermeabilization are the subject of studies in several countries, mainly in relation to the impacts on urban drainage systems which, during extreme weather events, cannot handle the large volumes of rainfall, causing floods and inundations. However, most studies address the impacts and their causes after the event, demonstrating the scarcity of studies regarding the prediction of the impacts of urbanization on the flood flow of urban rivers, especially in small municipalities. This highlights the need for research and the development of methodologies on this subject. With the aim of evaluating the potential impacts of urban expansion on the drainage system of the municipality of Medianeira-PR, the flood flows of the Alegria River microbasin upstream of the mouth of the Bolinha River were verified, both for the current urbanization parameters and for the total urbanization of the area included in the urban perimeter, considering the maximum occupation and impermeability allowed by current legislation. To this end, scientific works on the subject were analyzed, and granulometric tests of the microbasin soil were carried out, along with studies of legal provisions. The study area was mapped using digital elevation models, the soil type and its use were identified, and, using the Soil Conservation Service (SCS) method, the basin's flood flows were determined for return periods of 50 and 100 years. It was concluded that the urbanization of the region could increase the volume of surface runoff in the micro-basin by 10%, the clay soil makes it difficult to use infiltration systems, and municipal legislation lacks flood control mechanisms, which could overload the macro-drainage system and intensify floods and inundations in risk areas, highlighting the need for future interventions to mitigate the impact of this increase in flow volume.