Subsurface flow and associated oxygen transfer induced by turbulence in a gravel bed river

Abstract

A model for the subsurface flow and associated oxygen transfer induced by surface flow and slip velocity is presented in a gravel bed river. The shear velocity (U *) and hydraulic conductivity (K) were used to characterize the surface flow and subsurface flow, respectively. The subsurface flow field was described by using the Darcy and the Brinkman equations. The interaction between surface and subsurface flow can be represented by the slip velocity via the shear velocity (U *) and hydraulic conductivity (K). The effect of turbulence above the permeable surface on the subsurface flow can also be described by the Reynolds stress in terms of eddy viscosity (νt ). The model was found to substantially reproduce the experimental time-averaged subsurface velocity profiles. It was shown that turbulence penetrating through permeable sediments is limited to a thinner layer within a few centimetres from the sediment/water interface. This result can be useful to evaluate the effect of turbulence over the permeable surface on oxygen penetration into the sediment.