Time varying OL drainage parameters

In projects where you want to simulate the build out of an OL Drainage net­work over time, or changes in the OL Drainage time constants over time, then you can use this set of extra parameters. Without this set of extra parameters you would have to hot start your simulation at regular time intervals with the new OL Drainage parameters.

Note: If you specify time varying OL Drainage parameters, you will not be able to use any of the drainage routing methods that depend on the OL drain level. The preprocessor checks this and gives an error if you have specified

·         option 1 (routing based on levels), or

·         option 3 (distributed options) AND any of the distributed option codes are 1 (routing based on levels in these cells).

To activate time varying OL Drainage parameter options, you must specify the following extra parameters

Note: The time constants above refer to Inflow Time Constants. There is no option for time varying Outflow Time Constants

The dfs2 Drain Level is an elevation that can be specified using the following three EUM Data Units (V1 p. 135):

·         Elevation

·         Depth Below Ground (i.e. positive values)

·         Height Above Ground (i.e. negative values)

By default, the Time Series Types (V1 p. 147) is Instantaneous, but there is an extra option that allows you to used Mean Step Accumulated values if you want. The use of Mean Step Accumulated does not change the meaning of the item, but changes the way the values are interpolated.

Note: The code does not check for the time series type.

All specifications are printed to the projectname_PP_Print.log and project­name_WM_Print.log files.