Hjulstrom's diagram plots two curves representing (1) the minimum stream velocity required to erode sediments of varying sizes from the stream bed, and (2) the minimum velocity required to continue to transport sediments of varying sizes. this is a modified version of the diagram, showing only the transport segment. stream competence refers to the heaviest particles a stream can carry. according to hjulstrom's diagram stream competence depends on a) particle size. b) stream velocity. c) stream deposition. d) stream channel shape.