Why is running water the main force shaping the Apennine landscape?

Running water is the primary agent of erosion responsible for shaping the contemporary Apennine landscape because it acts upon a diverse range of rock types that exhibit varying degrees of resistance to water action.1

The physical geography of the range is defined by this interaction between water and the underlying geology. For instance, in limestone regions, the landscape is characterized by karst erosion, where water creates distinct crevasses. In other areas, such as those with clayey rock types, the landscape takes on a desolate appearance featuring frequent erosion of the calanchi, or badlands, type.12

While the Apennines exhibit characteristics of an early, or juvenile, stage in the cycle of erosion, the overall relief is a direct result of how these specific geological materials respond to the erosive power of water.1