Obviously rivers must flow downhill. The type of terrain it flows through will always vary. The river is always at its steepest descent in mountainous areas, and of course, that's where the rainfall is highest.
Danube river gradient
The Mississippi River is longer than the Colorado River.The Mississippi River
Take the elevation from an upstream point on the river and the elevation from a point downstream on the river. Calculate the difference in the two elevations. Measure the distance between the two points by tracing the path of the river. Divide the difference in the two elevations by the distance between the two points in order to get the slope of the river, or the river gradient.
If a river channel has a steep gradient, the river flows faster and has more erosive energy.
A river beginning high up in the mountains will fall sharply until the gradient levels out in the valleys. A river beginning in lower hills will naturally have a less steep gradient over all. Therefore, each river's longitudinal gradient will be different and there is no definitive answer.
The gradient of a river is the steepness of its slope.
A rejuvenated river is a river with a gradient that is raised by tectonic uplift.
A 'Rejuvenated' river is a river with a gradient that is raised by tectonic uplift.
pressure gradient
Concentration Gradient
A young river is very active. It is still at the upper course. It moves at a characteristic high speed that enhances its active down-cutting and under-cutting. Its competence is very high due to its speed. An old river on the other hand is characterised by its materials and also the topography of its course. The old river has lost its competence due to the gradient of its course. The speed is low compared to a young river.
It doesn't decrease, it increases. It only apears to decrease because the lower course of a river is smoother. Because of waterfalls etc in the upper course, it appears to be going quicker when actually obstructions, although creating a splash, decrease spped.