Velocity profiles and the structure of turbulence at the outer bank of a compound meander bend

- Curved channel flow caused Reynolds stresses to differ from straight channel norms
- Streamwise-lateral stresses as critical as streamwise-vertical stresses in this bend
- Local bank geometry can disrupt this pattern, with implications for bank erosion

Few studies have quantified near-bank turbulence at the field-scale in meander bends. As a result, details of the structure of turbulence at the outer bank of bends are poorly understood, despite recognized linkages among turbulence, bank erosion, and channel migration. This study uses high-frequency measurements of flow velocities to analyze the characteristics of turbulence in close proximity to the outer bank of an actively migrating compound meander bend. Results show that the structure of turbulence in the bend is linked to curvature-induced effects through the progressive advection of high momentum fluid toward the outer bank as flow moves through the bend. Vertical profiles of streamwise-vertical Reynolds stresses near the outer bank differ considerably from those in wide straight channels because of the effects both of curvature-induced helical motion and of local frictional effects associated with the complex bank morphology. The results of the study provide the basis for a conceptual model of the structure of outer bank turbulence in this meander bend.