Which Factor CANNOT Be Used to Determine the Depth of a Debris

Multiple Choice

Which factor CANNOT be used to determine the depth of a debris flow in a canyon it moved through?

A) bark battered off the upstream sides of trees up to that height
B) sand embedded in bark up to that height
C) rocks lodged in tree branches up to that height
D) the maximum height of sand eroded from the valley sides
E) the highest rocks on natural levees deposited by the flow