Final answer:
The difference in average velocities between Type 1 and Type 3 stream channels can be understood through the concepts of laminar and turbulent flow, and how flow rates are determined by the velocity of the stream and its cross-sectional area.
Step-by-step explanation:
The differences between Type 1 and Type 3 stream channels imply a difference in the average velocities of the streams flowing through them. When streamlines are closer together, as seen in figures within the text, this suggests a higher fluid velocity due to the decreased cross-sectional area through which the fluid flows.
This concept is linked to laminar and turbulent flow, where in a Type 1 stream, you are more likely to find laminar flow, indicated by smooth, continuous streamlines and likely a more uniform velocity. In contrast, a Type 3 stream channel might show signs of turbulent flow, with streamlines that break and mix due to higher speeds and possibly obstructions, leading to a broad range of velocities within the stream.
The flow rate (Q), described as Q = Av, where 'A' is the cross-sectional area and 'v' is the velocity of the fluid, also plays a role. A smaller cross-sectional area paired with a high velocity would indicate that the stream has a certain flow rate despite having a constraining area, reflecting a Type 1 channel. In contrast, a Type 3 channel, which may have a more substantial or irregular area with turbulent flow, might have a different flow rate despite potentially high velocities at certain points.