Characterizing Pattern, Profile and Dimension
Level I classification continues with pattern, profile, and possibly dimension analysis following the Valley type assessment. In the next series of slides for this FGM Module Section, images will be used to convey the dominant features of the A to G river types. Given that this is a Level I analysis, the presentation will not discuss bed material, or provide detailed illustrations of channel cross sections. In the Level II analysis, more attention will be given to methods for extracting values for Entrenchment Ratio and width to depth ratio.
Central to Rosgen classification is the analysis of many geomorphologic features, including the entrenchment ratio, width to depth ratio, Sinuosity, and slopes. Entrenchment Ratio is given as the channel width at Bankfull Depth and the Flood-Prone Width at double Bankfull Width. In the following slides many geomorphological descriptors are provided for the various channel types. If they are unfamiliar, please review Section 3
As explained earlier, the detail of most topographic maps and aerial or space based photographs will prove inadequate for precision measurement of dimension features such as channel width and depth. Pattern features such as Sinuosity, and profile features such as Valley slope and Channel Slope, are typically extracted from 1:2400 scale topographic maps and equivalent or better photos.
Image courtesy of Rosgen