Evaluation of Flood Control Design with Traditional and Sustainable Approaches in a Urban Basin Under Development, Supported by Integrated Modeling

Cities that have difficulties in managing their stormwaters will gradually degrade since the failure of drainage systems directly affects the operation of others urban systems, such as housing, sanitation and urban mobility. The disorganized urbanization process tends to favor the occupation of naturally flooded areas and produce extreme changes in land use, such as the removal of the natural vegetation cover and the significant increase of impermeable areas. These changes increase both velocity and runoff volume, what can overstress the drainage system previously designed and constructed to support planned urban stormwater patterns. The city of Rio de Janeiro, which is the second most populous city in Brazil, presents an urban-expansion process that aggravated the flood situation in several regions. When combined with recurrent events of very intense rainfalls, these regions suffer great losses. The theme of urban water management in metropolitan territory needs to be further studied in order to clarify the real challenges and promote the most diverse management perspectives in densely occupied watersheds, especially when administrative boundaries (and management decisions) disregard natural needs and environmental patterns. Thus, to address the challenges posed by uncontrolled urban growth in flood-prone areas, one should make use of not only a wider set of tools, but also consider the political factors that influence land use change processes.

The present work proposes the comparison of different urban drainage design alternatives for the Guerenguê River basin, located in an area of priority for the urban expansion of Rio de Janeiro city. Different hydrological-hydrodynamic simulation scenarios, comparing current and future situations, as well as flood control alternatives, were carried out with HIDROFLU and MODCEL software, both developed at the Federal University of Rio de Janeiro/UFRJ. Detention and infiltration measures were prioritized, seeking to mitigate the negative effects of urbanization on the hydrological cycle. Additionally, scenarios with climate change impacts over storm intensity and sea level were performed in order to establish project parameters in favor of resilience over time. The research shows the importance of integrated modeling in evaluating the effectiveness of different flood control approaches over the watershed.