A shallow section of a stream or river where water flows rapidly over rocks or gravel, creating surface turbulence and often a distinctive rippling sound. Riffles are important for stream ecology as they oxygenate the water.
From Middle English 'riflen' meaning 'to scratch' or 'wrinkle,' describing the scratched or wrinkled appearance of water flowing over a rough streambed. The term evolved to specifically describe these turbulent shallow sections by the 18th century.
Riffles are like the lungs of a river system – they're where streams 'breathe' by mixing oxygen into the water! Gold prospectors love riffles because the turbulent water naturally sorts sediments, concentrating heavy materials like gold in the gravel beds downstream.
Complete word intelligence in one call. Free tier — 50 lookups/day.