Levantamento e mapeamento do índice de risco de alagamento da Bacia do Riacho Reginaldo

Abstract

Urban floods are due, mainly, to excessive soil division with consequent surface impermeabilization, to occupation of riverine areas, to inadequate drainage works and to pipe obstruction with debris and sediments. According to the concept of sustainability, urban drainage approach should consider basin characterization, linking the occurrence of flood events and its effects with their causes. One way to characterize floods is interviewing affected neighborhoods. This study presents an Index of Flood Risk (IRA) applied to Reginaldo Creek basin (Maceió, Brazil). This index was developed from flood characterization indicators (frequency, magnitude, wideness, runoff generation). It also environmentally characterizes susceptible areas, via field trip observations. The IRA index results from the sum of four indicators that represent flood characteristics: Indicator of Flood Consequences, that evaluates flood depth; Indicator of Flood Probability of Occurrence, that evaluates the frequency of such events; Indicator of Flood Damage, that evaluates population density in flooded areas and; the Indicator of Flood Runoff Generation, that evaluates the capacity of runoff generation by floods. Twelve areas were considered susceptible to floods in the Reginaldo Creek basin, which were mapped according to the Index of Flood Risk. Such mapping helped on comparing flood effects in several areas in Reginaldo Creek Basin. Such information is powerful in subsidizing urban drainage planning or even in zoning floodable areas in the studied basin, which helps in prioritizing areas to apply drainage work interventions. It was observed in Reginaldo Creek basin that causes of frequent floods are river bank strangulation due to the presence of roads; presence of solid wastes in the drainage network and river bed siltation. Runoff increase is also remarkable probably due to chaotic urbanization and consequent basin impermeabilization.