online_modified_einstein:   Total sediment discharge by the Modified Einstein Procedure

References

  1. Einstein, H. A., 1950. The bed-load function for sediment transportation in open channel flows. USDA Soil Conservation Service, Technical Bulletin No. 1026, Washington, D.C., September.

  2. Colby, B. R. and C. H. Hembree, 1955. Computations of total sediment discharge, Niobrara river, near Cody, Nebraska. U.S. Geological Survey Water Supply Paper 1357, Washington, D.C.

  3. U.S. Bureau of Reclamation, 1955. Step method for computing total sediment load by the Modified Einstein Procedure. Sedimentation Section, Hydrology Branch, Project Investigations Division, July.

  4. U.S. Bureau of Reclamation, 1966. Computation of "Z's" for use in the Modified Einstein Procedure. Sedimentation Section, Hydrology Branch, Project Investigations Division, June.
RATIONALE

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The Modified Einstein Procedure computes total sediment load, consisting of bed material load and fine material load (wash load), by individual size fractions. It computes the measured and unmeasured portions of the total sediment load. As such, it is the most complete method of calculating sediment load.

The procedure requires the following input variables: (1) hydraulic flow variables; (2) bed material sizes; (3) measured sediment concentration; (4) bed material fractions in each of several size ranges, and (5) percentages of suspended material in each of several size ranges.

Consider the following:

  • A given sediment transport formula computes only bed material load, and not fine material load.

  • A given sediment transport formula may not be strictly applicable to the site of interest.

  • A field measurement (with a suspended sampler) provides a "measured" fraction of sediment load, but not the total sediment load.

  • The unmeasured portion of the sediment load may be a substantial fraction of the total sediment load.

  • The Modified Einstein Procedure is based on the Einstein bedload function.

  • The Modified Einstein Procedure computes both bed material load and wash load, and accounts for both measured and unmeasured loads.

Thus, the Modified Einstein Procedure eliminates the shortcomings inherent in sediment transport formulas and field measurements of sediment load.

Given the proper front-end/back-end unit conversions, the Modified Einstein Procedure can be used with SI units.

Given several sediment load measurements at different flow stages, the Modified Einstein Procedure can be used to develop a sediment rating curve, i.e., a curve of total sediment load (tons/day) vs water discharge (cfs) [or Metric Tons/day vs m3/s].

•    Total sediment load = Bed material load + Fine material load    •

•    Total sediment load = Measured sediment load + Unmeasured sediment load    •

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