Scenario Evaluation of Alternatives for Flood Control in the Anhangabaú Watershed, Brazil (PAP014950)

Código

PAP014950

Autores

Carla Voltarelli Franco da Silva, CRISTIANO DE PADUA MILAGRES OLIVEIRA, JOAQUIN IGNACIO BONNECARRERE GARCIA, LUIZ FERNANDO ORSINI DE LIMA YAZAKI, Orlando Natale, Ana Paula Zubiaurre Brites

Tema

Flood risk management in mega cities

Resumo

Flooding and overflows are common and recurring problems in several Brazilian cities, which usually undergo disorderly development. Their causes vary from increased impervious surface areas, deficiency / inefficiency of drainage structures and their maintenance, siltation of rivers, channel obstructions and climatic factors. This situation is even aggravated when occurred in large cities. The Anhangabaú Watershed lies in the central portion of São Paulo ? Brazil and covers a drainage area of 5.4 km². The region is highly urbanized and is crossed by an important north-south road connection. During heavy rain period, portions of this interconnection passage become compromised, disrupting the flow of vehicles, creating a chaotic situation for the population, as well as losses to the national economy.In seeking solutions to the problems of flooding in the basin, which have been studied for decades, the São Paulo City Hall hired Hydraulics Technology Center Foundation (FCTH) to evaluate the performance of two traditional alternatives already proposed for the region system drainage and to offer a new alternative, based on modern concepts of water resources management. Therefore 3 alternatives intended to mitigate the flooding problem in the lower valley were evaluated: (i) 2 flood detention reservoirs and reinforcement of main gallery system, designed to ensure safety against 25-year return period events; (ii) reinforcement of the main gallery and flow derivation tunnel leading to the Tamanduateí River for a 100-year return period; (iii) distributed linear retention spread over the watershed in stages of return periods of 10/25/100-years. The comparison of alternatives was given by a multi-criteria analysis based on six subjects, namely, alternative efficiency, prevented damages, permanent environmental impacts, temporary environmental impact, costs and public response. The evaluation of technical criteria analysis was based on a complex modeling network employing PCSWMM application, representing both road and drainage systems and their interconnections. The alternatives were simulated for different scenarios corresponding to a combination of drainage system, urban occupancy, adoption of LID (Low Impact Development) controls, modeling dimension and rainfall time series.Modeling outputs showed that all alternatives presented relevant results in solving the flooding at critical locations. However, that the alternative regarding linear retention offered better overall effect to solve the problems of flooding in the Anhangabaú Watershed.