What is the typical shape of stream valleys?

Stream valleys typically take on a V-shaped profile. This shape develops as streams erode their channels, primarily through the process of downcutting into the landscape, which happens when the flow of water carves into the soil and rock over time. The steep edges of the valley walls form a triangular shape when viewed from the side, resembling the letter "V."

The V-shape is most prominent in youthful or actively eroding streams that are still actively cutting into the bedrock or sediment. As streams mature or if they experience lateral erosion, their valleys may evolve further, but the initial formation reflects the V-shape due to the hydrological processes at work.

Other shapes like flat-bottomed or U-shaped valleys can occur, but they are typically associated with other geological processes, such as glaciation or the development of alluvial plains. Asymmetrical valleys may also occur, but they are less common compared to the classic V-shape that is characteristic of stream valleys.