Transport in a three-zone wetland: Flow velocity profile and environmental dispersion

•To find the velocity profile of the superficial flow through a three-zone wetland.•To determine the environmental dispersivity by a multi-scale analysis.•To analyze the effects of dimensionless characteristic parameters on the velocity profile and environmental dispersivity.•To illustrate the difference of dispersivity between the three-zone flow and three-layer flow.

To achieve better understanding of transport process in real waterways interacted with adjacent aquatic vegetation and riparian buffers, a three-zone model featuring the bank-effect is presented to character the water flow and environmental dispersion. Based on basic formulation in context of porous media flow, the velocity profile of a fully developed flow through the wetland is derived, with that for single zone and two-zone wetland flows recovered as special cases. The environmental dispersivity is determined by the approach of multi-scale analysis, with the effects of dimensionless parameters well illustrated. Application examples are provided to illustrate associated hierarchical structure for the critical length and duration of the contaminant cloud, and a comparison is made between the three-zone wetland and a corresponding three-layer wetland.