The shape of river valleys

2.5.2 MEDC - Sonoran desert

3.2 Fluvial processes

The shape of river valleys

  1. Long profile

    1. The long profile plots the height of a river against its course, which is how far it has flowed from its source
    2. Theoretically, the long profile has a steep gradient near the source, giving way to a more gradual slope farther downstream as potential energy is replaced by a larger mass

  2. Cross profile

    1. A cross profile of a river shows the cross section of the river at a particular point
    2. Cross profiles at different points on the river can be used to show how the river changes as it flows downstream
    3. Generally, the cross profile shows the valley becoming wider and flatter with lower valley sides

  3. Changes

    Property Upper course Middle course Lower course
    Channel shape Shallow & narrow Wider & deeper Widest & deepest
    Erosion direction Vertical Some vertical but more lateral Less erosion: only a little lateral
    Erosion type Hydraulic action, abrasion and attrition Abrasion & attrition All erosion much less important
    Transportation type Some traction & saltation at high flow Suspension mainly but saltation & traction still present Suspension dominant
    Deposition Large material Most material Fine material
    Load size Large Reduced Very small, but large amount