Which sediment characteristic is most influential in determining channel shape?

The average size of the sediment is the most influential characteristic in determining channel shape. This is because sediment size directly affects the dynamics of sediment transport and deposition within a river or stream system. Larger sediment particles, such as gravel, tend to be deposited in certain ways that create broader, shallower channels, while smaller particles like silt or clay can lead to narrower, deeper channels due to their ability to be carried downstream more easily.

Sediment size also influences the velocity of water flow; larger particles require higher velocities to be transported, whereas finer materials can be moved at lower speeds. This interplay of sediment size and water flow dynamics shapes the morphology of the channel significantly. As a result, the average size of sediment plays a crucial role in determining the overall form and structure of the channel.

In contrast, color, texture, and aging of sediment do not have a direct impact on channel shape to the same extent. While color may indicate mineral composition and certain properties, it does not influence hydraulic behavior. Texture refers to the surface characteristics which could affect other properties but are less critical than size in shaping channel morphology. Aging may change physical and chemical properties over time but does not directly influence the immediate hydraulic factors that shape channels.