Landscape shaping with curves

Hi guys,

I am a beginner in grasshopper, and I am working on a structure that can be controlled at the same time in transverse as well as longitudinal cross-sections (I have a reference curve to control these cross-section shapes) I can fully control the shape of the structure in transverse section, but when I try to combine it with control of the shape in longitudinal cross-section I have a problem of anchoring or snaping the structure to the ground level (in my case: to two base curves that I started creating the geometry with)

I want to control the shape in both cross-sections accoring to a reference curve. Can anyone help?

Thanks,

Philip Sailor