Hydraulic Boundary Conditions

This article describes the different hydraulic boundary conditions available in Slide, and should make it more clear when each of the boundary conditions would be best used.


The figure below illustrates many of the different boundary conditions:

Constant head:  ABC, EFG

No flow:  HI

Free surface:  CD

Note: The location of D is determined by the program as part of the solution, it is not defined by the user. It is the boundary between the saturated and unsaturated zones.

Seepage Face:  DE



Descriptions of each boundary condition can be found below: 

  1. What is the Constant Head boundary condition?

  2. What is the Nodal Flow boundary condition?

  3. What is the Seepage Face boundary condition?

  4. What is the Infiltration boundary condition?

  5. What is the No Flow boundary condition?


Also note the following tips regarding specifying boundary conditions:

  • When a boundary has no boundary conditions assigned to it, that boundary is an impermeable boundary.  
  • When assigning a "Seepage Face condition" or "Unknown Boundary Condition" for a node or a segment of a boundary, that section cannot have pressure greater than zero.  This means that whenever the water table rises to the level of that point, water can flow out of the model from that point (seep out).
  • Discharge sections are best put inside boundaries and not on them.