A river with large, smooth rocks on the bottom, small and medium sized sediment is moving downstream.

Question

Which conditions resulted in the erosion of larger rocks, like the one circled in the image? Check all that apply.
low gradient, low velocity
low gradient, high velocity
low gradient, high volume

Answer 1

To determine the conditions that resulted in the erosion of larger rocks in a river, we need to consider how the characteristics of the river's flow—gradient, velocity, and volume—affect the transport and erosion of sediment.

1. Low gradient, low velocity - This combination typically results in less erosion since the flow of water is slower and less capable of moving larger rocks.

2. Low gradient, high velocity - While a low gradient usually results in a more gentle flow, high velocity can contribute to erosion by increasing the movement of water, which can help dislodge larger rocks, so this condition could lead to some erosion of larger rocks.

3. Low gradient, high volume - Higher volume of water can increase the force of flow even at a low gradient, potentially leading to the erosion of larger rocks as well.

Based on the explanation above, the conditions that may have contributed to the erosion of larger rocks in the river are:

• Low gradient, high velocity
• Low gradient, high volume

These conditions provide sufficient energy and flow characteristics to facilitate the erosion of larger rocks.