Attribute: SICK [-] (node-wise) (vertical and 3D models only)

With this data type the node numbers along a possible free seepage face are defined. It is not necessary to specify a value for the seepage rate (columns 1 to 14 of the model file).

The point at which a potentiometric surface of, for example, a dam naturally intersects with the atmosphere is typically situated higher than the surrounding water table. This distance between these two points can result in a “free outflow boundary” or seepage face.

When the SICK attribute is assigned to the nodes along a boundary where the potentiometric surface intersects the atmosphere or is higher than the surrounding groundwater elevation, the resulting seepage is automatically calculated. During the calculation, the seepage nodes initially have a fixed potential head equal to the geographic elevation of those nodes. The calculation can then iteratively change the seepage rate for the boundary condition at these nodes as the potential head changes, and for example, change the seepage rate to zero when the potential head drops below the elevation of the node. Seepage boundary conditions can also be switched on and off iteratively for different time steps using transient SICK data.

A node that has been assigned the attribute SICK must not simultaneously be assigned the attribute GLEI, POTE, or VORF!