This paper focuses on characterizing proposed human-built topographic forms and describing them parametrically. Two basic approaches exist for characterizing shape algorithmically: parametric descriptions, which describe discrete geometries, and non-parametric methods, which for the most part work on fields. This paper offers a brief overview of the range of parametric modeling options for topography, a set of criteria that need to be fulfilled for any successful landform design system, and a primitives and operators approach that offers some specific advantages in the AMG context.