A conceptual model of the relationship between channel characteristics and discharge

Abstract

SUMMARYRegression equations with the form y =f(q), where y is a channel characteristic and q is a discharge of a particular frequency are widely used in fluvial geomorphology. They imply that channel geometry is related to a dominant discharge. For this to be so, the river must be 'in regime' i.e. its characteristics must fluctuate about a mean condition which is effectively stationary at the time scale considered. The static regression-dominant discharge approach does not fully describe the relationship between channel characteristics and discharge and an alternative model is proposed with the form y ( t ) = l ; h ( u ) . q ( t -u ) d u . This model states that channel form is a product of the whole series of discharges experienced by the channel. The dominant discharge-static regression approach provides a working approximation of the relationship between channel characteristics and discharge only when temporal variations in q are small or when y is insensitive to variations in q.

Rational regime model of alluvial channel morphology and response

“…Regime models are predicated on the assumption that a single discharge and associated equilibrium sediment transport rate are sufficient to predict the channel form of active stream channels, which may be approximately true when discharge fluctuations are small, but is unlikely to be generally applicable to alluvial streams (Pickup and Rieger, 1979). Furthermore, the functional relation between discharge and sediment transport capacity depends not just on the magnitude of sediment supply, but also on its calibre.…”

Determination of bankfull discharge magnitude and frequency: comparison of methods on 16 gravel‐bed river reaches

“…The bankfull discharge corresponds to the river level just before it starts to flow out of its main channel and over its floodplain (Wolman and Leopold, 1957;Kilpatrick and Barnes, 1964;Riley, 1972;Pickup and Reiger, 1979;Williams, 1978;Harrelson et al, 1994;McCandless and Everett, 2002).…”

Channel response to extreme floods: Insights on controlling factors from six mountain rivers in northern Apennines, Italy

“…A major issue has been the role of large floods in comparison to more frequent floods with lower magnitude. Several studies have contributed to developing the concept of effective and formative discharge proposed originally by Wolman and Miller (1960), pointing out that (i) it may be more appropriate to consider a range of discharges rather than a single formative discharge (Pickup and Rieger, 1979;Surian et al, 2009) and (ii) large floods may play a major role in certain fluvial systems such as steep channels (Johnson and Warburton, 2002;Lenzi et al, 2006), in ephemeral streams in arid and semiarid areas (Harvey, 1984;Reid et al, 1998;Hooke and Mant, 2000), and in bedrock channels (Jansen, 2006). Another major research question concerns the factors controlling channel response to a large flood event.…”