Warning System Based on Real-Time Flood Forecasts in São Paulo, Brazil (PAP014951)

Código

PAP014951

Autores

CRISTIANO DE PADUA MILAGRES OLIVEIRA, Carla Voltarelli Franco da Silva, André Sandor Kajdacsy Balla Sosnoski, Pedro Ludovico Bozzini, Daniela Mendes Rossi, Sandra Uemura, FLAVIO CONDE

Tema

Flood forecasting and early warning systems

Resumo

Floods are natural events that can cause victims and various social and economic losses. These events are originated from intense rainfall that exceeds soil infiltration capacity leading to major water runoff that surpasses the capacity of drainage systems causing flooding and overflows. In particular, at highly urbanized basins, the problem becomes even more complex since it involves land use issues, not only by raised flood peaks caused by broadened impervious surface areas, but also by increased vulnerability to flooding due to highest population densities located in flood prone areas. Yet there are frequent cases when the impacts of these floods are aggravated by lack of consistent information, which implies poorly conceived projects, bad maintenance and faulty decisions by public officials, investors and society in general. Based on this scenario, the São Paulo City Hall (PMSP) has invested in a flood management system for evaluation, monitoring, forecasting and warning in order to promote stormwater management efficiency and effectiveness of preventive and corrective actions. Therefore, PMSP maintains a technical assistance contract with the Hydraulics Technology Center Foundation (FCTH). At first, this partnership addressed activities of atmospheric monitoring of precipitation using radar and land precipitation monitoring, as well as channel and reservoir levels through telemetric network and weather forecast. Seeking to understand and evaluate the response of basins and major drainage structures to different precipitation, a rainfall-runoff model followed by a hydraulic model are now being applied to predict outflow and flood extents in critical watersheds, in order to support the management of the impacts of extreme hydrological events.PMSP selected six priority independent watersheds with distinct characteristics that represent about 15.5% of municipal territory area for the initial implementation of this technology, namely Aricanduva, Água Espraiada, Cabuçu de Baixo, Mandaqui, Morro do S and Pirajuçara. Selected watersheds already hold flood control structures, but still experience flood related problems, except Mandaqui.Hydrological modeling of the subcatchments and hydraulic modeling of the main channels were performed employing PCSWMM (CHI), which consists of a set of solutions associated with the core calculation SWMM5 EPA, incorporated into a modern GIS engine. The models were calibrated for each watershed adopting recent extreme event data. As a result, PCSWMM delivers profiles and hydrographs along simulated channels, reservoir states, flood inundation extents and affected buildings. In addition, there is a PCSWMM Real-Time module that discloses prediction results for flood inundation sites based on radar rainfall forecasts, taken every 10 minutes to a prediction horizon of 3 hours. These outputs are addressed to the Emergency Management Center (CGE) in real time on the internet, with an intuitive graphical web-interface, easily allowing access to information and analysis of complex problems by technicians.