When does a stream become graded?
A)When erosion and deposition are in equilibrium.
B)When a local base level controls the stream.
C)When a river achieves a longitudinal stream profile of a steeper upstream portion.
D)When its basin becomes rejuvenated.

Question

Quizplus · Accepted Answer

A stream becomes graded when erosion and deposition are in equilibrium, meaning that it is not actively cutting down or building up its channel. This typically occurs when a stream has reached a state of dynamic equilibrium with its surrounding landscape, with its discharge and sediment load balanced by the downstream transport capacity of the channel. Choice B is incorrect because a local base level, which is typically a large body of water that a stream flows into, can influence a stream's profile but does not necessarily cause it to become graded. Choice C is incorrect because a stream does not necessarily have to have a steeper upstream portion to be graded, though a graded stream will typically have a smooth longitudinal profile with a consistent slope. Choice D is incorrect because basin rejuvenation can cause a stream to adjust its channel and become ungraded, by increasing its energy and sediment load.

When Does a Stream Become Graded