topography

1. N-UNCOUNT Topography is the study and description of the physical features of an area, for example, its hills, valleys, or rivers, or the representation of these features on maps. 地形学

2. N-COUNT The topography of a particular area is its physical shape, including its hills, valleys, and rivers. 地形[usu sing, with poss]

The topography of the river's basin has changed significantly since the floods. 洪水过后，这条河的流域地形已经明显改变了。