What is the primary factor that influences a stream's competence?

The primary factor that influences a stream's competence is stream velocity. Competence refers to the maximum size of particles that a stream can transport. As the velocity of the stream increases, its ability to carry larger sediment also increases. This is because a higher velocity provides more energy to overcome the forces of gravity and friction acting on the particles.

When a stream flows faster, it generates greater lift and drag forces, enabling it to move larger and heavier particles along its bed and through the water column. Thus, stream velocity is a crucial determinant of how much sediment can be transported, ultimately influencing the stream's competence.

While factors such as particle size, water temperature, and the direction of the river may have an impact on sediment dynamics and river behavior, they do not directly determine the competence of a stream as effectively as viscosity does through flow speed. Understanding how stream velocity impacts competence is vital for comprehending sediment transport and river morphology.