Metodologia para determinação de volume de detenção em pequenas bacias urbanas: o caso do córrego Wenzel, Rio Claro/SP

With the accelerated urbanization process of Brazil from the 50s, there was a disorderly occupation of spaces and consequent soil sealing. Unlike this growth, the support capacity of urban environments has not evolved in the same way, generating negative environmental impacts to the citizens. Among these impacts are the effects of flooding. In order to minimize the negative effects of extreme precipitation over cities, the government invests in corrective measures, like compensatory techniques on urban drainage, which have as a basic principle the retention and infiltration of the rainfall, dampening the peak flow and runoff. An example of applying these techniques in urban areas are the detention basins, commonly called large pools. The hydraulic design of these structures is dependent of complex data and variables, and projects involving small areas generally use simplified methods for defining the reservoirs volume of the storage (Tassi, 2005). One of these methods is presented in this study, which relates to the percentage of soil sealing to the specific storage volume (m³/ha) in combination by applying the hydrological model of the Rational Method and analyzing regional rainfall and soil occupation over the basin. Within this context, the basin of the Wenzel stream, which is located amidst the urban area of Rio Claro/SP, also presents the problems related to human occupation in its valley. Thus, by the method presented has been adjusted a curve correlating the percentage of impermeable area and the specific volume of a detention basin. For the current situation of Wenzel Basin with 82% of impermeable area, and return period of 10 years, the specific volume is 262.1 m³/ha. The presented method is consistent with the results of other studies in the area, and the expression obtained allows estimating the volume of storage required to match hydrograph pre and post-occupancy. It presents itself as a useful tool in the planning stage of...

Aplicação de modelos hidrológicos para avaliação de reservatórios de retenção e detenção combinados à obra de recuperação do canal de macrodrenagem no controle de cheias em uma bacia hidrográfica urbanizada

The aim of this paper was to evaluate the effect of retention and detention reservoirs along with the regulation in channel flow upgrade on flood for an urban watershed located at Rio Claro, SP. For this purpose, modeling and simulation techniques were applied for runoff determination and its propagation in channel. The Soil Conservation Service – SCS hydrologic model as well as Pulz and non-linear Muskingum-Cunge model were used. The software IPHS1 was applied on simulations. The results pointed out that the combination of retention increasing and detention reservoir implementation (120,000 m3, corresponding to 1.5% of the watershed area) with the streamflow upgrade (n decreasing from 0,04 to 0,02) can minimize the flood on the investigated Servidão watershed. Further, after the proposed intervention, the flood was eliminated for the investigated times of recurrence: 5, 20, 50 and 100 years. The prognostic indicated that the available area occupation had a minor effect on flow increasing due to the observed high urbanization.