What is the rate of change in elevation of a stream or river?

• A. Stream gradients
• B. Elevation
• C. Slope
• D. Cartesian coordinate system

Answer: (A)

The rate at which a stream’s elevation changes downstream is described by its gradient. Gradient measures how much the elevation drops per unit distance along the stream, essentially the steepness of the river’s path. It’s calculated as the change in elevation divided by the distance traveled downstream (Δelevation/Δdistance), with typical units like meters per kilometer. For example, a drop of 30 meters over 1 kilometer gives a gradient of 30 m/km (about a 3% grade). This rate affects flow velocity, erosion, and sediment transport. Elevation itself is just a height value, not a rate, and Cartesian coordinates describe positions rather than how elevation changes along the stream. While slope is related, gradient is the term most directly used for the rate of elevation change along a stream.