ICFM6 - International Conference On Flood Management

Data: 17/09/2014 à 19/09/2014
Local: São Paulo - Brazil

Flood Prone Areas in Santo Amaro Da Imperatriz Municipality (PAP014757)

Código

PAP014757

Autores

Daniel Etchegaray Mendes, Pedro Luiz Borges Chaffe

Tema

Urban Floods

Resumo

The Santo Amaro da Imperatriz municipality (SAIM) is located in the downstream area of Cubatão do Sul river basin (CSRB) in Santa Catarina State, Brazil. Since the city has suffered with flood, the knowledge about flood prone areas in is critical for better design practices and disaster prevention plan. The objective of this paper was to analyze the changes in inundated areas due to different design rainfalls for the Santo Amaro da Imperatriz municipality. The CSRB with 740 km2 is the main drinking water supply for more than 700,000 inhabitants of the region. Water level and discharge data were obtained from 2 gauging stations: the Poço Fundo station, localized upstream of the SAIM with a 57 years historical record; and the ETA CASAN station, localized downstream of the SAIM and with a 19 years historical record. Design rainfall of 20, 50 and 100 years return period were obtained using IDF curves for the location and the SCS method. In this study we divided the total basin area in 4 subbasins: the upper reach of the Cubatão do Sul river (425 km2); the lower reach of the Cubatão do Sul river (42 km2); the Matias river basin (86 km2); and the Vargem do Braço basin (187 km2). Design flood discharge for each of the 4 selected subbasins was calculated using the Triangular Unit Hydrograph. Flood routing and inundation were calculated using the HEC-RAS model. Channel sections geometry were extracted from DEM with 30m obtained through the Epagri website. The calibration of the HEC-RAS model was done by comparison of the discharge and water level obtained with the model and the measured ones in the Poço Fundo station and the ETA CASAN station. The errors for the simulated water level were within 1% and 10% for the Poço Fundo station and the ETA CASAN station respectively. The simulated inundation areas also accurately corresponded to the neighborhoods which were reported to being flooded in past flood events. In general, the inundation behavior and inundated area found for the 20, 50 and 100 year return periods were very similar. Therefore, the 20 year return period event might be causing many of the inundations occurring in the area. In some of the downstream cross sections we observed two peaks for the water elevation due to the different arrival time of the flood wave coming from the different subbasins. Despite the reasonable results, our simulations were limited by the lack of more detailed river cross sections and for not considering some of the hydraulic structures such as bridges.

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