"地形学上的" can be translated as "topographical" or "in terms of topography".
"Topographical" is an adjective that directly relates to topography, the study or description of the physical features of an area, especially in relation to its surface shape.
"In terms of topography" is a phrase that can be used to introduce a discussion or description related to the specific aspects of topography.
For example:
"Topographical features" refers to the physical characteristics of the land surface.
"We need to consider the area in terms of topography for our construction project." means we need to take into account the physical features of the land when planning our construction.