river energy in lower course

The lower course of a river has the largest (kinetic) energy because of the high river discharge and velocity.
However, deposition occur in the lower course as the slope of the river bed become gentle that encourage deposition of river loads. Increase in deposition may reduce the velocity of the river and hence less energy brought by the river. Compare to the upper and middle courses of the river, there is a very large river discharge and less friction produced by the rough river bed (rough river bed incresae friction and lower the river velocity) in the lower course that can produce huge energy although increase in river loads hinder the river flow.
Also, depodsition takes place at the river bed which will not affect the surface river flow.
Therefore, the largest energy found is in the lower course of a river.

deposition occurs in the lower course because of the change of gradient.

2009-06-20 17:03:37 補充：
"the largest energy" refers to the volume of sediments that carried by the river.
lower course > upper course

冇錯。
河游下流係水多能量多流速大，但衰在沉積物仲多。
所以會有deposition.