CALIBRATION OF A ONE-DIMENSIONAL SEDIMENT TRANSPORT MODEL ON A TWO-DIMENSIONAL SCOUR PROBLEM

One-dimensional sediment transport models tend to be easier to parameterize and require fewer assumptions about sediment transport processes than two-and three-dimensional models. However, since scour and deposition in channels is often a three-dimensional process, one-dimensional models clearly do not fully describe the processes that occur in many, if not most, channels. Furthermore, channels have lateral variation in particle size. However, in a one-dimensional sediment-transport model, a single sediment source characterization is required at each cross-section to maintain continuity of sediment in and out of a cross-section. Therefore, it is necessary to include empirical relationships to describe scour and deposition in banks and overbanks. This paper describes parameterization and calibration of HEC6T, a one-dimensional sediment transport model, to a large flow in Pueblo Canyon at Los Alamos National Lab. In July 2001 this canyon was subjected to a flow, which significantly scoured the channel in some locations and deposited sediment in others. We have been able to estimate scour and deposition by comparison before and after elevations at monumented cross-sections. In addition, high-resolution topographic data are available from both before and after the event. For the reach studied, scour occurred in the upper portion of the reach while deposition occurred in the lower portion. Also, scour occurred in some overbanks and deposition occurred in other overbanks. The HEC6T model was able to simulate the trends observed in the field. It was also interesting to note that the model predicted scour at peak discharge in cross-sections, where deposition ultimately occurred.