Long Profile – The gradient of a river from its source to its mouth
A profile is an outline of something.
Just like a person has a profile, a river has one too. The long profile of a river is from top to bottom, or source to mouth (see below):
A long profile shows how a river changes over its course.
The upper course, where the river starts, is usually in an upland area. The river is narrower and faster-flowing here, its bed is usually V-shaped, and the particles carried by the water are relatively large.
In the lower course, the land is generally much flatter. The riverbed is more U-shaped and the particles in the water are more likely to be fine sediment, as erosion has broken down the larger pieces.