Determinação experimental do coeficiente de Manning em trecho do rio Pitimbu, Natal-RN

Abstract

The fluvial system is the result of an adaptation to the morphological characteristics of the catchment. In the water course, an irregular configuration of contours and curves reveals a dynamic process of equilibrium aiming at an optimum dissipation of the mechanical energy available. In the process of downstream flow, the resistance forces that oppose movement are associated with the dissipation of available energy. In addition, the hydraulic resistance is related to the characteristics of the velocity distribution along the wetted perimeter. Experimental studies demonstrate that the resistance, represented by the Manning coefficients (n), depends on factors associated to the flow, bed material, bed forms, gutter geometry and vegetation (species, density, geometry). The resistance can be obtained experimentally in the field. The objective of this study is to analyze the hydraulic resistance associated with the hydraulic characteristics of a stretch of Pitimbu River, at Prudente de Morais Avenue, Natal/RN. Flow measurements in the transverse section was made by using electromagnetic equipment, and revealed high flow variability through the plants stems in the close downstream regions, where reverse currents and turbulence occurred. Measured flow discharge and Manning coefficient was 0.274 m3/s and 0.127 respectively.