ABSTRACT
RESUMO O processo de urbanização resulta em alterações no ciclo hidrológico prejudiciais à população. Para amenizar esses efeitos, as técnicas compensatórias em drenagem urbana visam à maior sustentabilidade hidrológica na expansão urbana. Nesse sentido, este artigo teve como objetivos avaliar, por meio de modelagem computacional, o efeito da adoção dessas técnicas na escala de lote e da bacia hidrográfica e avançar com diferentes possibilidades de concepção de projeto. A modelagem foi realizada para diversos cenários, considerando a implantação das técnicas de forma isolada e combinada. Os parâmetros utilizados na modelagem visaram verificar possibilidades extremas de aplicação, de modo a disponibilizar dados para balizamento de projetos reais. As chuvas avaliadas possuem variadas durações e intensidades, facilitando a extrapolação dos resultados deste trabalho para bacias hidrográficas de diferentes escalas. Os resultados das simulações indicam potenciais benefícios na drenagem urbana oriundos do uso dessas técnicas no lote, com mais efetividade para as menores chuvas de projeto. Esse foi o caso dos cenários que avaliaram os jardins rebaixados isoladamente ou combinados em série com um reservatório de lote e os cenários de pavimentos permeáveis na calçada que receberiam o escoamento superficial do lote adjacente. Também foi verificado que a combinação paralela de um reservatório de lote com as dimensões propostas pela legislação municipal e um jardim rebaixado em 0,07 m seria capaz de neutralizar, hidrologicamente, os impactos da ocupação do lote para todas as chuvas de projeto analisadas, entretanto o reservatório proposto pela legislação municipal, quando adotado isoladamente, quase não atuou na escala da bacia..
ABSTRACT The urbanization process results in detrimental changes in the hydrological cycle to the population. In order to mitigate these effects, compensatory techniques in urban drainage aim at increasing hydrological sustainability in urban expansion. In this sense, this paper intended to, through computer modeling, evaluate the effect of the adoption of these techniques on site scale and at the watershed scale, as well as to discuss different design concepts. The modeling was performed for different scenarios, considering the implementation of the techniques isolated and combined. The parameters proposed for modeling aimed to check the extreme possibilities for their application in order to make data available for actual projects. The rainfalls have been evaluated for different durations and intensities, thus facilitating the extrapolation of this study results for variable watershed scales. The modeling results pointed to potential benefits on the urban drainage due to the compensatory techniques adoption at the lot scale, with the property owner being capable to easily control the smaller design rainfalls. This was the case of the scenarios with raingardens isolated or combined in series with a lot reservoir or the scenarios where a permeable pavement on sidewalk received runoff from the adjacent lot. The parallel combination of a lot reservoir proposed by the municipal legislation and a raingarden with only 0,07 m depth would be capable of hidrologically neutralize the impacts of the occupation for all project rains analyzed. Nevertheless, the same reservoir proposed by the municipal legislation, when used isolatedly, showed little or none benefits on the basin scale.
ABSTRACT
Aims: In recent decades, Ho Chi Minh City, Vietnam, frequently has been affected by local floods and inundation from heavy rainfall. Conventional flood mitigation measures such as building flood gates and upgrading sewerage systems have been implemented but problems persist. The objective of this research is to assess another approach for flood control measures, namely Sustainable Urban Drainage Systems (SUDS), with application to the Nhieu Loc - Thi Nghe Basin, located in the central part of Ho Chi Minh City. Methodology: A combination of the Stormwater Management Model (PCSWMM) and interviews with 140 households was used to assess the efficacy and acceptability of four of the most popular SUDS: Rainwater harvesting, green roofs, urban green space and pervious pavement. Thirteen SUDS and urban build-out scenarios were simulated under 6 design storm conditions. Results: PCSWMM results showed that inundation from intense rainfall could be reduced with proper land-use control, specifically by maintaining imperviousness at 65% or less of the surface area. With respect to SUDS performance, green roofs were best at reducing peak runoff (22% reduction), followed by pervious pavement, urban green space, and rainwater harvesting systems. Regarding environmental improvements, as represented by reduction in total suspended solids load, urban green space was best with 20% of the solids load removed compared to the base case scenario, followed by green roofs, pervious pavement, and rainwater harvesting. The household interviews revealed the majority of people preferred pervious pavement to the other SUDS options and the least preferred option was green roof technology. Conclusion: Considering the combination of water quantity and water quality controls, it seems that green roof technology was the best performer for this area of Ho Chi Minh City, followed by urban green space, pervious pavement and rainwater harvesting. However, green roof technology also was the least favored option for the public and stakeholder acceptance will impact SUDS implementation.