USGS Regional Curves

Bankfull channel dimensions of cross-sectional area, width, mean depth, and the related streamflow velocities tend to increase linearly with increases in drainage area (Leopold et al. 1964). When stratified by stream type, plots of bankfull channel dimensions prove even more useful for estimating similar channel dimensions for ungaged areas.

For example, selected average bankfull channel dimensions for four hydro-physiographic regions are shown in Figure 99 (PDF, 157 kb, 1 p.) (Dunne and Leopold, 1978).

The majority of these streams are alluvial channels. The bankfull channel dimensions that have been collected and field-calibrated at stream gages should be plotted similarly in order to build a supporting database useful for refining estimates of bankfull channel dimensions for ungaged areas.

As one constructs local relationships and curves from the gage data, the plot of bankfull channel dimensions by drainage area should not only be integrated or stratified for a hydro-physiographic province, but also by stream type. Follow the progression in Figure 100 (PDF, 45 kb, 1 p.) for development of regional curves (Leopold,et al, 2000).

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