Resistência do fluxo em um canal com características de leito misto

Abstract

Obtaining data and organizing information about the flow resistance in channels is an expensive task that requires a lot of time, since information on the roughness of channels bed is scarce and imprecise. The use of empirical equations, using coefficients to obtain resistance values is a strategy widely adopted by researchers on the subject. However, each stream has particularities and different sources of roughness, that is, equations obtained with data from the studied channel data tend to present better performance when compared to those present in the literature. There is a range of parameters that can be used as roughness coefficients, and those related to the bed sediment diameter are the most adopted. However, there is a line of investigation that, considering the use of a Terrestrial Laser Scanner (LST) equipment to obtain the topography of the channel generating the standard deviation of the bed elevation, allows using this parameter - the standard deviation - as a measure of roughness. This study sought to evaluate the performance of the standard deviation of the bed elevation as a roughness parameter of a reach in the Arroio do Ouro watershed, located in the city of Morro Redondo, Rio Grande do Sul state, to estimate the flow resistance. The study site is characterized by a good distribution of large boulders, both on its bed and on its banks, composing the macroroughness of the site, making this reach very suitable for the study of flow resistance, especially when using the standard deviation of the bed elevation as a measure of roughness, since this parameter has a strong relationship with macroroughness. This study presents a relevant scientific innovation, which consists in the use of a Terrestrial Laser Scanner to carry out a topographic survey of an open channel, going against the common use of this equipment, which is mainly used indoors. A topographic survey was obtained with great precision and quality using this equipment, with very low discrepancies, in the range of 0.01 meters. As for the standard deviation of bed elevation, the study found satisfactory results, even better than the equations widely adopted in the literature.