Fundamental Research on sediment transport has been conducted at NCCHE in past years. NCCHE researchers proposed formulas for determining the fractional transport capacities of bed load and suspended load, which take into account the hiding and exposure effects among different size classes. In addition, formulas for the calculations of sediment deposit porosity, settling velocity, movable bed roughness and sediment transport over steep slopes were also developed. These formulas were calibrated using a large data set that included experimental and field measurements.
Wu and Wang’s Formula
for Movable Bed Roughness
(ASCE, J. of Hydraulic
Engineering, Vol. 125, No.12, 1999)
Wu, Wang and Jia’s Formula
for Fractional Bed-Load Discharge
(IAHR, J. of Hydraulic
Research, Vol. 38, No.6, 2000)
The newly proposed Wu et al’s (2000) sediment transport capacity formulas were tested independently against many different experiment and field data, including Brownlie’s (1981) data sets, and Toffaleti’s (1968) data sets. Wu et al.’s formulas were also compared with some existing formulas, such as Ackers and White’s (1973) formula and its modification by Proffit and Sutherland (1983), Engelund and Hansen’s (1967) formula, Yang’s (1973) formula, and the SEDTRA module (Garbrecht, et al. 1995). Wu et al.’s formulas can provide reliable predictions for the fractional discharges of bed load, suspended load, and bed-material load.
Comparison of Bed-Load Transport Capacity Formulasusing Brownlie’s Uniform Bed Load Data
| Error Ranges |
Percentages (%) of Calculated Transport Rates in Error Ranges |
||||
| Van Rijn |
Engelund & Fredsfe |
Bagnold |
Meyer-Peter & Mueller |
Wu et al. |
|
| 0.8£r£1.25 |
14.8 |
21.4 |
21.4 |
21.3 |
38.7 |
| 0.667£r£1.5 |
25.3 |
37.4 |
38.9 |
39.4 |
59.3 |
| 0.5£r£2 |
44.0 |
54.1 |
57.2 |
66.2 |
80.1 |
Comparison of Bed-Material Load Transport Capacity Formulasusing Brownlie’s Uniform Bed-Material Load Data
| Error Ranges |
Percentages (%) of Calculated Transport Rates in Error Ranges |
||||
| Ackers & White |
Yang |
Engelund & Hansen |
SEDTRA |
Wu et al. |
|
| 0.8£r£1.25 |
37.3 |
33.4 |
33.6 |
36.6 |
40.4 |
| 0.667£r£1.5 |
57.9 |
56.6 |
55.4 |
59.1 |
62.7 |
| 0.5£r£2 |
82.4 |
76.6 |
77.0 |
78.1 |
81.3 |
Note: r = calculation / measurement.
Comparison of Bed-Material load Transport Capacity Formulasusing Toffaleti’s Nonuniform Bed-Material Load Data
| Error Ranges |
Percentages (%) of Calculated Transport Rates in Error Ranges |
||||
| Modified Ackers-W. |
Modified Engelund-H. |
Karim |
SEDTRA |
Wu et al. |
|
| 0.5£r£2 |
5.6 |
27.8 |
42.7 |
56.9 |
57.9 |
| 0.333£r£3 |
11.1 |
40.3 |
63.5 |
73.1 |
76.1 |
| 0.25£r£4 |
20.8 |
49.0 |
73.3 |
80.9 |
85.2 |