ICFM6 - International Conference On Flood Management

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

Flood Mapping in Urban Area Using Hec-Ras Model Supported by Gis (PAP014412)




Filipe Viezzer da Silva, Nadia Bernardi Bonuma, Patrícia Kazue Uda


Urban Floods


Floods are among the most damaging natural disasters in Brazil, not only financially, but also in human terms. In 2011, floods have affected about 2.5 million people, causing 900 deaths and more than $ 1 billion in economic losses. In the Santa Catarina state, in the 1991-2010 period, about 5.7 million people were affected and 4,054 deaths were reported as results of these phenomena. This reality highlights the necessity for studies that can support flood control measures. Among these measures, flood maps have a non-structural character and can assist decision-making in relation to urban planning, increasing of public awareness regarding risk areas and evacuation routes. The Itajaí River Valley is known for flood events since its occupation and figures among the areas with the highest number of flood records in Santa Catarina. This study mapped the flood extent of Rio dos Cedros city urban area, medium Itajaí Valley, through the hydrodynamic mathematical model HEC-RAS, supported by a GIS. The following data were used: digital terrain model, hydrography map and orthorectified aerial image (1:10,000 scale), Cedros River discharge time series and field discharge measurements. Simulations were performed for events with return period of 2, 5, 10, 20, 50 and 100 years, and for a flood event occurred on 08/09/2011. The results indicated that the roads and buildings in the surroundings of the Cedros River bridge and the Ouro Creek and its tributary confluence region are more susceptible to flooding. In addition, show the absence of urban planning and the occupation of the watercourses natural flood areas. The model presented an underestimated result when compared to the flooded areas recorded in the 09/08/2011 event. This behavior may be due to the return of the Cedros River water by urban drainage system, and the possible backwater of the Cedros River in the Ouro Creek and its tributary. This study demonstrates the potential of use HEC-RAS model and GIS with high resolution spatial data for mapping highly susceptible flood areas.

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