Sediment transport calculations

1D Sediment Transport Solver is based on the predictions of the sediment transport equations.  All sediment transport predictors can be subject to quite significant errors due to the difficulties in obtaining accurate sediment transport measurements and due to the stochastic nature of sediment transport.  Typically the best sediment transport predictors will achieve predictions within half to twice of measured values in about 70% of cases. Caution must be exercised therefore in the use of sediment transport predictions.  For 1D Sediment Transport Solver, either calibration of the model should be performed, or sensitivity tests should be undertaken.

The revised Ackers-White sediment transport equation is recommended in the absence of data to suggest another equation is more accurate for that site.  The Engelund-Hansen equation is also appropriate.  Use of the Westrich-Jurashek equation should be limited to cohesive sediments or for assessing deposition on rigid boundary channels.  The 1973 Ackers-White equation should be used for sensitivity analyses or to ensure compatibility with earlier work using that equation.  The modified Parker equation accounts for size fraction interaction in sediment mixtures and is applicable to both uniform and graded sediments – it is recommended for use in the case of widely graded sediments transported as bedload.

Sensitivity tests can be performed by changing the equation (not to Westrich-Jurashek, however, which is not designed to predict transport in sand or gravel bed channels), or by changing the calibration coefficient 'K'.

The calibration coefficient 'K' should not be changed from 1.0 unless for sensitivity tests or, in extreme cases, for resolving problems with calibration.  Values outside the range 0.3 to 3.0 would indicate severe problems in calibration.