Why would you find waterfalls on the upper course?

Waterfalls are commonly found in the upper course of a river due to the steep gradient and the erosion processes that occur in this region. As the river flows over hard rock, it can create vertical drops where softer rock erodes away faster, leading to the formation of a waterfall. Additionally, the energy of the fast-flowing water in the upper course enhances the erosion, contributing to the development and maintenance of waterfalls.