SEDIMENTOLOGICAL FLUID DYNAMIC “TRINITY”: WHY IS THIS CONCEPT SO IMPORTANT?

Morphodynamic systems are governed by a unique coupling between fluid flow, sediment transport, and bed morphology (Leeder, 1983; Best, 1993). The dynamic physical processes that link fluid flow, sediment transport, and bed morphology largely dictate (i) the spatial and temporal changes in flow conditions, (ii) the rate of sediment transport, and (iii) large and small-scale adjustments in bed topography. Thus, unraveling how morphodynamic systems operate through time and space rests with gaining a deep understanding of all the physical processes that build the foundation of the sedimentological fluid dynamic “trinity” (SFD). In the context of bedforms, each of the components and physical processes controlling the SFD “trinity” are deeply intertwined thus making it very difficult to isolate the effects of one component relative to the others. For instance, water in motion develops turbulent sweeps and bursts that entrain sediment into the flow (Heathershaw and Thorne, 1985), which generates differential transport of grains. These regions of erosion and deposition ultimately lead to the development of a bedform (i.e. bed morphology change). Distortions on the bed (i.e. bedforms) then change the flow and turbulent characteristics of the fluid flow, which in turn induce a new condition for sediment transport that begins to modify the originally generated bedform. Hence, to fully understand morphodynamic systems one must gain a clear understanding of the numerous feedback loops continually operating in the vicinity of the bed. Therefore, this presentation will utilize the results of combined flow bedform laboratory experiments conducted at the Ven Te Chow Hydrosystems Laboratory, University of Illinois to help characterize many of the feedback loops embedded within the SFD “trinity”.

Best, J. L. (1993) In: Turbulence:Perspectives on Flow and Sediment Transport,Wiley,New York, 61–92.

Heathershaw, A. D. and Thorne, P. D. (1985). Nature, 316, no. 6026, 339–342.

Leeder, M. R. (1983) In: Modern and Ancient Fluvial Systems, 6 of Special Publications of the International Association of Sedimentologists,Blackwell Science Ltd, 584.