The file for this example, Gymea All Model Example - Full Unsteady.drn, is located in the folder C:\ProgramData\Drains in the Full Unsteady examples.  If this folder is hidden, from File Explorer select the View tab and tick the Show Hidden Items box).

To adapt the model in Example 1 to full unsteady hydraulic operation it is necessary to specify a length for each overflow route, rather than a time lag, as DRAINS will use the full unsteady flow equations of momentum and continuity for routing flow through the overflow route. These are added in the overflow route property sheet.  For sag pits, it is necessary to specify a weir representing the barrier over which stormwater will flow to escape from the sag. This can be a horizontal weir, a parabolic weir representing the vertical curve of a road, or some other relationship (table of depth vs discharge). Finally it is necessary to add upstream and downstream levels for the invert of the overflow path. DRAINS can provide these automatically, but they should be checked.

The results of a run equivalent to the Design results shown in Example 1 are presented below. The Horton (ILSAX) model is applied, but ERM and IL-CL model calculations can also be made.

When there is limited overland flow such as a well designed drainage network, the Lite hydraulic model storm results are similar to those for the Full Unsteady hydraulic model, as there are limited storage and tailwater affects.  Differences are more pronounced in the 1% AEP runs, or in situations where flooding is an issue.  Note that the critical results are the same storm, but this is not always the case.

If you set up a model to run with individual storms, as in Example S2, DRAINS will operate in its older form, presenting 'worst-case' results. It will be possible to plot long-sections for overflow routes, as well as pipes and channels.