DETERMINING STREAMFLOW CHARACTERISTICS BASED ON CHANNEL CROSS-SECTION PROPERTIES

Channel dimensions have proved to be valid indicators of streamflow characteristics. Use of channel geometry requires definition of a relation between the desired flow characteristic and stream-channel size based on data at gaging stations; estimates of the flow characteristic can then be made a ungaged sites by obtaining the channel dimensions. Regional analyses have been made in many western states and in some eastern states by the U.S. Geological Survey. These analyses are summarized and some results are compared. Three reference levels have been used to define the channel dimensions. The principal differences between the channel-geometry approach and conventional approaches that use basin characteristics are that (a) the ungaged site must be visited to measure the channel size before an estimate can be made and (b) some field training is required before an individual can identify the channel reference level. Variability among channel measurements by trainined individuals effectively increases the error of the estimate over the standard error of the estimate defined during calibration. The increase is dependent on the variability in channel type, but extremely variable conditions could increase a calibration error of 42 percent to an application error of 55 percent. (Author)