We propose a hierarchical representation for the morphology of a terrain. The basis of our morphological model is a decomposition of the terrain model, composed of the stable and unstable manifolds defined by its critical points, called a Morse-Smale complex. We propose a compact dual representation of the Morse-Smale complex and we define new simplification operators of the terrain morphology, which act on such representation. Based on these operators, we define a hierarchical morphology-based representation for a terrain, that we call a Multi-resolution Morse-Smale Complex (MMSC). Results from our implementation of the MMSC are shown.