levee,

I haven't used the current version of Slope/W, but I would imagine that it's as simple as creating a soil layer or layers that matches the section of the flood wall. Set the strength parameters for the wall to infinite strength.

Jeff

If you don't understand how a slope stability program uses material strengths and have a lot of experience, you should probably get someone else to do the analysis.

A levee is not the time to learn how slope stability software works.

I agree with GeoPaveTraffic, levee evaluation should be performed by someone with experience.  Scour and erosion are major issues, as well as undrained strengths and seepage pressures/groundwater modelling.  There was a very good article in the ASCE monthly a year or so back, I believe by Mitchell or Duncan.

That said, modelling structural elements with Limit Equilibrium methods is tricky.  Here is what Slope/W recommends:

Summary

Taking into account the effect of a sheet pile wall or other similar structural elements in a SLOPE/W stability analysis.
 
Description

When a potential slip surface passes through a sheet pile wall, for example at the base of an excavation, the shear resistance of the wall will affect the factor of safety.
 
Resolution

The best way to represent the sheet pile resistance in SLOPE/W is with a Line Load applied just above the slip surface. It is up to you as the user to select and specify the appropriate magnitude of the Line Load. Remember that the magnitude of the Line Load needs to be per unit length of the wall. You should not try to model the sheet pile wall as a material.

SLOPE/W can only give you the margin of safety against potential failure. If you are interested in the structural integrity of the sheet pile wall by assessing the shear and moment distribution within the wall, then you will need to do a soil-structure interaction analysis using SIGMA/W.