O sistema de drenagem como eixo estruturante do planejamento urbano: caso da bacia hidrográfica do Rio Acari

Abstract

In the last decades, the Metropolitan Region of Rio de Janeiro, Brazil, like most other urban centers in underdeveloped countries, observed a strong vector of disordered urban growth, often associated with inadequate planning. Several areas of environmental value, especially flood plains, were occupied informally and irregularly. In addition to the fact of being exposed to flood hazards, these occupations contribute significantly to amplify the flood itself, due to increased runoff generation and higher flood peaks. Soil waterproofing and the suppression of natural spaces previously used by rivers are the main drivers of this process. Floods may cause: people to be exposed to sewage and garbage, exposing them to waterborne diseases, losses to buildings and their contents; traffic blockage; and economic losses and incapacity of recovering from these losses (in successive events); and environment and urban degradation. Thus, this work discusses the role of urban drainage and flood control as a preceding driver in urban planning, taking water as a structuring axis for city development. Therefore, seeking to support this perception, a bibliographic review was made to find historic elements that put in evidence the significance of this proposition. In addition, a critical urban watershed in the Metropolitan area of Rio de Janeiro was modelled, and hydrodynamic simulations were performed to estimate urban gains due to flood mitigation, in relation to habitation, sanitation, transportation, urban facilities and economy. The mitigation strategies, where urban planning was not sensible to the presence of water, were based on sustainable urban drainage concepts integrated with the use of the urban open spaces system, improving resilience to floods and allocating water volumes in adequate multifunctional spaces for re-organizing flood flows.