Efeito da rugosidade no transporte de sedimentos em escoamentos superficiais utilizando canal hidráulico

Abstract

Accelerated and unplanned urbanization alters the urban hydrological cycle, causing major impacts such as increased sediment transport in surface runoff, also increasing economic, social and environmental impacts in urban areas. Nowadays, there is a search for solutions that minimize the impacts caused by the increase in the amount of sediment and surface runoff in urban areas. In addition to the need to find solutions to problems related to sediment transport in surface runoff, there are difficulties in carrying out work in the field, which is generally laborious, requires a lot of effort and is expensive. In this way, the use of scale models makes it possible to complement studies on sediment transport in surface runoff, facilitating the control of some variables that are difficult to control on real scales, in addition to reducing research costs and time. In this study, experiments were carried out on a reduced scale in a hydraulic channel in the laboratory of the Federal University of Alfenas to verify the effect of roughness on sediment transport in surface flow. The tests were carried out in an acrylic channel for two different roughnesses, in triplicates for three different flow rates that varied from 0.15 to 0.25 L.s-1 and 25 grams of sediment were used per test. The results showed that the peak mass discharges of the pollutograms were much lower for the R2 roughness than for the R1 roughness, where there was a decrease of 98.09% in the Q1 flow, 99.10% in the Q2 flow and 99.17% at flow rate Q3. Furthermore, the temporal distribution of sediments in the pollutograms was much smaller for roughness R1, where a large part of the amount of sediment was collected in a very small interval of time, between 12 and 30 seconds, and for roughness R2 the amount of sediment was distributed over a much longer period of time. The study made it possible to verify that with the increase in the roughness of the channel covering material there was a significant decrease in the peak mass discharge of the pollutograms and that the amount of sediment present in the surface flow decreased due to the increase in sediment retention caused by the material with the greater roughness, showing that the greater the roughness of the channel bottom material, the longer it will take to transport the entire amount of sediment.