Final answer:
The velocity of a stream's flow is directly proportional to its potential to cause erosion. Higher velocities can carry more sediment and have greater erosional power, while slower velocities lead to sedimentation.
Step-by-step explanation:
The relationship between a stream's velocity and the rate of erosion is significant. As the velocity of the water in a stream increases, its ability to erode soil and rock also increases. This can be explained through the equation Q = Av, where Q is the flow rate, A is the cross-sectional area of the stream, and v is the average velocity of the water. Therefore, the flow rate is directly proportional to the velocity of the water. Fast-flowing rivers can carry more sediment and have greater erosional power, leading to wider and deeper channels over time. Conversely, when a river's velocity decreases, sedimentation can occur because the river's capacity to carry particles also decreases.