How are riffles and pools formed?

Answer 1

The usual spacing between pools, areas of deeper water, and riffles, areas of shallower water, is usually very regular, being 5-6 times that of the bed width. The pool is an area of greater erosion where the availiable energy in the river builds up due to a reduction in friction. Energy is dissipated across the riffle area. As a higher proportion of the total energy is then needed to overcome friction, the erosive capacity is decreased and, except at times of high discharge, material is deposited.

Answer 2

Riffles are formed in shallow areas of a stream or river where the water flows faster over rocks or gravel, creating small, turbulent waves. Pools are formed in deeper areas where the water slows down and deepens, often creating calmer, still water. Both riffles and pools are important habitats for aquatic organisms and play a role in stream ecology.