Resistência ao fluxo em canais íngremes com leito de cascalho e formação de camada resistente.

Abstract

The present study presents an experimental investigation of flow in a steep channel with a bed-gravel. In steep slope rivers two flow conditions arc observed, the first one, the most common condition, when the water runs through the gravel layer and the second one, in flood occurrence, when the surface of the water stays just being above of the gravel layer. It was verified that for the flow through the gravel layer, the equation proposed by Stephenson estimates satisfactorily the flow, i f the friction factor K of the gravel has an appropriated value to the form of the bed material. For the second flow condition, the resistance variation of the gravel-bed was analyzed, The equation developed by Ugarte and Madrid for the bed resistance calculation by the modification of Manning coefficient n and the equations of Hey and Bathurst for Darcy-Weisbach coefficient f9 had been evaluated and these equations had showed to be satisfactory in limited conditions of bed material size and slope. The armor coat formation was also investigated, where the gravel-bed consisted by sediments with more than one size. By conclusion, the armor coat can be formed by the removal of the fine sediments from the surface, remaining only the large sediments or by the surface paving with the presence of fine sediments protected in the interstices.