Bed-load transport model based on fractional size distribution

Abstract

Two models based on the fractional size distribution approach, used in conjunction with the excess discharge theory, have been developed by using bed-load data collected from the Roaring River (Rocky Mountain National Park, Colorado) during the summer of 1995. The first model is based on the critical discharge value of individual fractional (IF) sizes, IF model (for log-normal and nonlog-normal size distribution modes), while the other is based on critical discharge value for total (combined) sizes, total fractional (TF) sizes model (for log-normal and nonlog-normal size distribution modes). The performance of the log-normal size distribution based models was tested with data from the Roaring River, Rich Creek, and Fourmile Creek (three Colorado streams), whereas the performance of the nonlog-normal size distribution based models was tested using Pitzbach River data. The performance of the models was also tested by comparing their results with the Inpasihardjo fractional size distribution based model. For all tests, the TF model performed better for both the log-normal and nonlog-normal grain size distributions.Key words: fractional size, critical discharge, IF model, TF model, discharge theory, Roaring River.