A study of flow dynamics and implications for benthic fauna in a meander bend of a lowland river

Abstract

Channel curvature and riffle-pool bathymetry in meandering streams control complex hydrodynamic and morphodynamic processes. This study investigates how spatial and temporal heterogeneities in flow hydraulics influence benthic fauna in a meander bend of a lowland sand-bed river. Spatial heterogeneity of riverbed morphology and secondary flow, induced by channel curvature, make pools hydraulically more diverse compared with riffles. Numerical simulations demonstrate that velocity reversal between riffles and pools in this meander bend produces spatially variable flow with complex temporal variations. Patterns of macro-invertebrates indicate an increase in population density from riffle to pool, reflecting an increase in diversity of abiotic factors. For most invertebrate species the observed patterns persisted during temporal variations of the flow. Considerable changes were observed only in some groups with specific preferences.