Abstract
Sediment transport and stream discharge are two of the natural procedures which affect the hydromorphological profile of a watercourse. Measurements of water discharge, bed load transport rate and suspended sediment concentration were conducted in Kosynthos River and Kimmeria Torrent –two intermittent streams– in north-eastern Greece. The total sediment concentration was calculated, in both streams, by means of various nonlinear regression equations and by means of the formulas of Yang, after calibrating the coefficients of the formulas. In the computations according to the Yang formulas, two different states were examined regarding the incipient motion: one considering and one disregarding the critical conditions. The results obtained from Yang’s multiple regression-derived equations had a better fit compared to the original equations and were acceptable in both cases. Ultimately, two counterparts of Yang’s stream sediment transport formulas were constructed and made available to the readership. The comparison between the calculated and measured total sediment concentrations was achieved by means of several statistical criteria. The results indicate that the modified formulas of Yang can be successfully used for the determination of the total sediment concentration in Kosynthos River and Kimmeria Torrent.
Highlights
One of the long-lasting problems hydraulic engineers are faced with is understanding and modeling the processes that govern sediment transport in streams
The objective of this study is to redetermine the arithmetic coefficients of the total sediment transport rate formulas of Yang based on field data of Kosynthos River and Kimmeria Torrent, using multiple regressions, and create modified equations that will provide substantially more accurate calculations of sediment concentration in these streams
The logarithmic total sediment concentration, logcF, was set as the dependent variable and the following auxiliary variables x1, x2, x3, x4 and x5 were set as the independent variables: x1 = log(wD50 /v) x2 = log(u∗ /w) x3 = log(us/w − ucr s/w) ucr s x4 = log us
Summary
One of the long-lasting problems hydraulic engineers are faced with is understanding and modeling the processes that govern sediment transport in streams. Perennial rivers have a continuous flow throughout the year, intermittent or seasonal rivers flow at specific wet seasons of the year when there are sufficient water resources, while the flow of ephemeral streams emanates only from surface runoff or snowmelt. Williamson et al [5] took this one step further by developing a standardized protocol based on field-based procedures, and on regionally calibrated hydrologic models, to classify ephemeral, intermittent, and perennial streams in the area of Kentucky, USA. Sefton et al [6] created heat maps using spatial analysis in order to classify the hydrological state of headwaters of the Thames River basin in the UK
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