Why does overland flow often lead to the formation of stream channels?

In hydrologic sciences, overland flow occurs when the rate of rainfall exceeds the soil's infiltration capacity, causing water to collect and move across the land surface. This process is inherently inefficient because the large surface area of the landscape creates significant resistance to water movement.1

To overcome this resistance, the flowing water tends to incise the substrate, a process that leads to the formation of a channel. This transition from overland flow to channelized flow is a fundamental response to rainfall input, as concentrated flow increases stream power and allows for more effective erosion and transport of material. Over time, this dissection of the landscape by channels facilitates the differentiation of hills from valleys. In environments with sparse vegetation and intense rainfall, this conversion is often accelerated, leading to the rapid multiplication of channels and the development of complex drainage networks.12