ICFM6 - International Conference On Flood Management

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

Best Management Practices as Alternative for Flood and Urban Stormwater Control in a Changing Climate (PAP014390)




Newton Celio Becker de Moura, Paulo Renato Mesquita Pellegrino, José Rodolfo Scarati Martins


Floods in a changing climate


Global climate models regarding the predicted scenarios of Greenhouse Gases (GHG) emissions, forecast a general increase in intensity and frequency of extreme rainfalls. Advanced studies in regional and local scales attest this intensification with greater spatial and temporal precision. The increase in rainfall associated with urban growth and more impervious surfaces, will lead to unprecedented impacts on drainage infrastructures, with high risks of flooding. Projections by the National Institute for Space Research (INPE) for Greater São Paulo, which already suffers from severe floods every summer, indicate a likely increase in the number of days with heavy rainfall until the end of the century. INPE also estimates that, between 2070 and 2100, a regional rise in temperature of 2 ° C to 3 ° C could double the number of days with heavy rainfall (over 10 mm) in the city of São Paulo and its metropolitan area. Considering the current scenario of urban sprawl and heavy rains, which both tend to worsen imminently, conventional solutions for stormwater management are still the dominant model in São Paulo and in Brazilian cities. Public administrators, policymakers, contractors and professionals - Engineers, Planners and Landscape Architects - still rely on stormwater detention and usual solutions for drainage infrastructures as the only suitable alternative, even with its growing costs and evident inefficiency in water conservation. In fact, detention ponds, known locally as big pools", were found to be very successful to prevent floods in the Greater São Paulo, and thus to mitigate material loss of population, traffic and other issues related to the limited conveyance of water in urban streams. However, when considering the hydrological cycle and natural processes, not to mention urban and social impacts, this strategy has proven to be ineffective. The immediate problem is solved in terms of hydraulics, but with the floods, pollution throughout the watershed is drained into detention ponds, which hold not only the surplus water, but trash and siltation. Then, numerous drawbacks become frequent for the operation and maintenance of these facilities, such as obstructions, unpleasant odor and unattractive landscape, which often result in rejection by the surrounding neighborhood. Facing the need of adaption to the future scenario, cities have the opportunity to perform an infrastructural transition when adopting stormwater Best Management Practices (BMPs) as a sustainable, resilient and landscape friendly solution. This paper presents a qualitative and quantitative comparison between BMPs techniques and usual detention reservoirs as flow control strategies. Regarding a case study urban watershed in Greater São Paulo, where two reservoirs with total volume of 19.200m3 were built, porous sidewalks and bioretention elements have been located in the contribution area within this basin. The retention volume of these proposed techniques considering their average porosity corresponds to 42% of the reservoirs capacity. It is then confirmed the stormwater BMPs viability and suitability as alternatives to adapting cities to climate change, but their efficiency relies on a design that takes into account the specific local environment."

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