Estudo de áreas urbanas susceptíveis a fenômenos de inundações, enchentes e alagamentos na cidade de Alegrete-RS

Abstract

According to IBGE data (2010) about 84,4% of the brazilian population lives today in urban city centers. The accelerated growth of the urban population generates in the urban space a serie of interventions, whereas the development of the infrastructure of cities can’t keep up this uncontrolled growth. Thus, the poorer population end up settling in inappropriate places, such as banks of streams, slopes, among others, contributing to the increase of irregular homes in regions that offer risk to the population. The city of Alegrete, located on the western border of the state of Rio Grande do Sul, constantly is affected by flood phenomenons, because, as well as several brazilian cities, the same also has a high number of people living in urban area. Because of the relevance of this problem, this project is based on informations worked with local organs to analysis vulnerable regions to these events, interviewing residentes with a help of a questionnaire. Perceives in this aspect, the precariousness of these locations with respect to infrastructure, because there is a very big deficit on the drainage system, many are damaged and clogged by trash. According to the majority of the interviewed population, floods tend to occur very frequently, between three to five years, and normally in the summer, especially in November. However, according to data from the Ibirapuitã River flows and quotas raised in the ANA, it was found that the greatest flow rate which has occurred in Alegrete it was in April, and the month with the highest incidence of events is October. Therefore, starting from the central objective of evaluating the areas and critical points within the urban area of Alegrete, was defined by mapping, seven critical places susceptible to flooding in the municipality, determining the scope of the events in these regions. Subsequently, using the statistical method of Gumbel, you can design periods of future returns and get the flows that are likely to occur, it is obtained a very short turnaround time of only two years, taking into account critical values for early flood with quota from 10.8 m and flow of 900 m³/s. From this, it can be seen that the floods are worryingly frequent, affecting a big part of the urban population. So, it is necessary that occupation control measures of preservation areas must be adopted by municipality and intervention measures in populated areas be applied, like alert systems and zoning, containment construction, revitalization of the River banks, among others.