Pond with various depth and various slope

Hi

I am about to create a pond with various depth, and various slope from bottom to elevation / terrain.

 How can I create a slope where it changes from 50% (1:2) to 20% (1:5).

By using "Create 3D Line By Slope To Terrain Model", I get a 3d line in 3d model view which I cant edit. (teh idea was to create one for each slope and complex them together).

Any Ideas are most welcome :-)

I am using Powercivil SS4 for Denmark vers. 08.11.09.878

Regards

Sigfus