Future Scenarios: Analysis of Susceptible Areas to Floods and Mass Movements

Abstract

The cities' migration process, leveraged by the rural exodus, contributed to the triggering of infrastructure problems, basic sanitation, occupation of susceptible areas, among others. In this sense, the proper planning of cities is fundamental to overcome the challenges faced by these urban agglomerations. Given these considerations, this paper aims to determine scenarios of the urban expansion of the city of Novo Hamburgo - RS, from 2015 to 2030. The modeling of Cellular Automata, within the Dynamic EGO software, was applied to analyze the viability of these scenarios concerning areas susceptible to flooding and mass movements in the city. Therefore, the urban spots of 2009 and 2015 were used to calibrate the weights and parameters of the variables used: distance from vegetation areas, distance from the drainage system, distance from the road system, altitude, and declivity. Based on the results, the construction of four future prognostic scenarios (2030), were built and then crossed with the susceptibility charts of the Geological Survey of Brazil, in order to identify the expansion against areas susceptible to flooding and mass movements. The results of the 2015 simulation reached similarity values of 0.80. Future scenarios showed a total growth of 3.9% in the study area, mainly concentrated in rural areas, through the expansion of existing spots and the formation of new nuclei. The urban territory composed of medium and high density, and the adjacent areas unfit for occupation, did not allow large expansions of the main urban area, but subtle growth to the south towards the flood areas near the Sinos River is visible; in the northern region, where the terrain reaches high slopes and in the west where a region of wetlands is concentrated. Crossing with susceptibility charts expressed that 7% of predicted expansion areas will occur in areas characterized as highly susceptible to flooding or mass movement. Thus, planning and supervision are the main tools for defining guidelines for an appropriate urbanization process.