Initial runs

Initially the model should be developed and run using the Flood Modeller 1D Solver without employing the sediment computations.  This should ensure that convergence in the hydraulic computations is satisfactory and that predicted water levels are appropriate.  Cross-sections may need to be extended from those used in the 1D model, because sedimentation may increase maximum flood levels.

It is recommended that a single sediment size and no bed updating is used in an initial sediment simulation which, if run times are long, can be for only a short, representative period. The results of this run should then be checked to ensure that the sediment inflow quantities are sensible, and that the overall behaviour is as expected.

The model can then be made more complex, and thus more representative of true conditions, by adding these features as appropriate:

• more size fractions for well graded sediments, and hence use of the SORTED algorithm
• more comprehensive description of the bed material by including variations from section to section
• use of the 'NEW' option for determining the sediment distribution entering at the inflow boundaries
• bed updating initially using the method 1, graduating to method 3
• addition of cohesive sediment fractions
• specifying dredging or sections with hard beds