Final answer:
The statement is false; streams with broad, shallow channels and narrow, deep channels generally have a slower flow velocity compared to those with semi-circular channels where flow velocity is greatest.
Step-by-step explanation:
The statement that streams with broad, shallow channels and narrow, deep channels have a higher flow velocity than do those with semi-circular channels is false. According to fluid dynamics principles, flow velocity is greatest where streamlines are closest together, which occurs when a fluid is forced through a smaller cross-sectional area, such as what happens with semi-circular channels often found in naturally eroded riverbeds.
The change in kinetic energy results from the work done on the fluid to push it into the narrower channel. Conversely, broad, shallow channels typically result in slower water movement due to a decrease in flow velocity caused by the increase in channel width and depth and a reduction in gradient as the river moves downstream from its source. As a river or stream widens, the current slows, sedimentation increases, and the water becomes warmer.