To start an unsteady flow run, an estimate of the initial conditions (flow and stage) is required at every model node. This is most often obtained by carrying out a steady state run at the proposed start time. However, steady state simulations may also be a valid modelling technique under certain conditions.
Two methods are available within Flood Modeller to compute steady flows. The Pseudo-Timestepping Method uses the Preissmann 4-point scheme, whereas the Direct Method uses a quite different and highly accurate solution technique.
Topographic data, including channel cross-sections and structure dimensions for example, are assembled into a datafile. This datafile represents the channel network system which may be very complex; it may be looped or branched and contain many interacting flow paths. The datafile will also contain the appropriate boundary conditions at the upstream and downstream extents of the model.