Rivulet instabilities appear in many engineering applications. In absorption equipment, they affect the interface area available for mass transfer, and thus, reducing the efficiency. Here, computational fluid dynamics are used to reproduce the meanders and braids in rivulets flowing down an inclined channel. Fast oscillations of the meander (f = 5.6Hz) are observed at low flow rates. At greater flow rates, an analysis of the transversal velocity in the retraction waves shows the effect of the surface tension, which causes the braiding phenomenon, and thus, the reduction in gas-liquid interface area.