Avaliação do impacto da ocupação urbana sobre as características hidrosedimentométricas de uma pequena bacia hidrográfica de encosta

Abstract

The objective of this research was the characterization of two small areas in different urbanization stages in a small urban hillslope basin with a total area of 0.53 km2. Two fluvio-sedimentometric stations and a pluviometric one were installed to characterize the maximum, mean and minimum discharges during the raining and dry periods, the sediment yield and also the transported material particle size analyses. The data were collected and analyzed between May 1st and December 20th , 2003 with 8 registered events at the less urbanized area and 7 events at the urban area. The sediment yield characterization was done by composing the relation of the liquid discharges with the solid discharges and the overland flow volume was also considered. The studying area and the sediment yield parameters were determined from the rating curve, which related the product of the superficially flowed volume and the peak discharge by the transported solid discharge; and the total superficially flowed volume by the total transported solid discharge. The bed load transported material and the ones transported by the storm were characterized through the particle size and sedimentation analyses. The suspended sediment mean concentration was determined through the weighting and filtering method and the laboratories analyses determined that the samples are from sandy origin. The results were analyzed and compared between the two measurement structures and they were also compared to other studies. It was observed that the sediment yield and the transported sediment characterization were as expected. The mean sediment yield to the urbanization stage area was 0.141 (t/ha.day) and to the urban area it was 0.271 (t/ha.day).