Why does the stream bed of a river become more uneven as the slope of the river becomes steeper?

Question

Why does the stream bed of a river become more uneven as the slope of the river becomes steeper?

Answer 1

as the force of the water becomes greater the direction the water takes is usually the path of least resistance making some areas of the river bed lower an more washed then others.

Answer 2

The flow of the water becomes faster and the sand, pebbles and small rocks carried by the water act as an abrasive and dig into the bottom of the river.  The softest areas get eroded away faster than the harder areas creating an uneven river bed.