chapter 3 fundamentals of fluvial geomorphology and stream ...

midwestern experience, while Rosgen's experience began insteep, mountain streams. In addition, Schumm's (1977)classification does not specifically include incised channels, whichare included in Rosgen's (1994) F and G classes. Figure 3.15includes C, D, DA, and E classes, and could be expanded toinclude all of Rosgen (1994) classes. The point of Figure 3.15 is todemonstrate that moving from class to class is a somewhatpredictable morphological response that manages energy,materials, and channel planform to re-establish the balancebetween the local capacity of the channel to convey water andsediment, and the discharge and supply of sediment fromupstream.Figure 3.15 – ChannelClassification CombiningAspects of Schumm (1981)and Rosgen (1994)Thorne et al. (1997) point out that many classificationsystems fail to account for dynamic adjustment or evolution of thefluvial system. Downs (1995) developed a comprehensive systemthat incorporates the classifications of Brice (1975) and Brookes(1981), and builds on their earlier work by linking observed trendsand patterns of adjustment to the fluvial and sediment processesresponsible for driving channel change (Figure 3.16). Adjustmentbasedclassifications like that of Downs differ fundamentally frommorphology-based schemes in that each system requires theobserver to determine the current stability status of the channeland the nature of channel adjustment processes. Because datamay not be available to document change, these schemes requiresound judgment on the part of the engineer, who must inferprocesses and trend of adjustment from channel form.60 Fundamentals of Fluvial Geomorphology and Stream Processes