Rivers and their valleys have long been a source of contemplation and wonder. They are not only key geomorphic agents, but they are also economically important, acting as transportation arteries, sources of irrigation water and food, and as generators of hydropower. We also use rivers for drinking, waste disposal, and for a variety of recreational activities. Many geomorphologists consider running water to be the most dominant and important geomorphic process – shaping landscapes everywhere. Even in deserts, running water is often the most important and widespread geomorphic agent.

Most valleys have a stream or a river at their bottom. In ancient days, it was thought that water simply “found” its way into preexisting valleys, forming rivers there. Geomorphologists now know that most valleys were formed by the rivers currently within them, which moved sediment out and carved the valley over time.

Deals with watershed geomorphology and characteristics, including hierarchical structure of a draiange basin, morphological parameters, hypsometry, stream order, Horton’s laws, stream power, longitudinal stream profile, hydraulic geometry, drainage density, drainage pattern, lag time, and time of concentration.