Fluvial scour and incision: models for their influence on the development of realistic reservoir geometries

Abstract: The three-dimensional geometry of fluvial sandbodies may be very complicated. Factors influencing this complexity include th processes of fluvial scour and incision, both of which can promote local or widespread increases in sandbody thickness. Incision, as caused by downstream relative base-level fall, produces entrenched valleys that control the location of subsequent alluvial deposits. A simple model is presented that attempts to quantify the scale of this extrinsic incision and, in turn, highlights everal sedimentary implications ofbase-level fall. In contrast, scour is an intrinsic process common to all fluvial systems, and is promoted by constriction, curvature or confluences within the major channels. Existing empirical el tionships that predict fluvial sandbody width from thick-ness are oversimplistic, failing to consider the modification ofsandbody dimensions by such intrinsic processes. At low aggradation rates sandbody thickness may exceed channel bankfull depth by 100%, due purely to the effects of scour. It is proposed that future fluvial width:thickness databases should stem from the classification of deposits according to the aggradational regime during their deposition. This will encourage the specific recognition of scour and incision, particularly in coastal plai