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What Are Large Sweeping Curves in a River Channel?

Rivers almost never follow straight paths. Instead, they venture off in long, sweeping curves, at times nearly looping and backtracking. These are natural occurrences due to the build-up and erosion of the shoreline as the river flows through. Typically, these wild, divergent turns occur anywhere the river has to go down a slight decline, around a natural obstacle or through a fine grain soil that erodes, but sticks together well enough to form banks.

Meanders
- The large, sweeping curves that naturally occur in a river channel are called meanders. The term comes from a river in modern-day Turkey known to the ancient Greeks as Maiandros, or Maeander. The river was notable for its extremely windy and twisty path. The name of this river gave rise to the word "meander," a noun referring to a winding path, and a verb meaning to wander aimlessly, or following a winding or intricate course.
Causes
- While it's easy for water to run straight down steep declines, meanders that begin as rivers are required to take a turn due to a gentle slope, an obstacle or fine soil. Over time, as the river continues to flow through the area, the curve moves farther and farther out due to the water sweeping sediments to the inside portion of the curve and eroding the outside of it. Eventually, this deposit and erosion cycle results in the convoluted path that most long rivers take.
Motion of River Water
- The water within the riverbed naturally cycles from the inside of the curve to the outside, down and across the bottom of the bed and back up to the inside of curve. This circular motion causes the outer edge of the curve to move farther by having the water sweep down and away at the outer curve, while carrying sentiments and other materials from the outer side and the bottom of the riverbed to the inside of the curve.
Shortcuts
- Occasionally the loops and curves of a river become so loopy and twisted that the ends of two separate curves begin to touch. Once this happens, and the cumulative erosion of the outer curves increases on both sides, the loops merge and create a shortcut. Here the water begins to run straight through that shortcut and ignore the loop completely,
Entrenched Meanders
- Over the course of millions of years, there has been a tendency for rivers to cut deeper and deeper into the rock, so much that there is an actual change in elevation between the river bed and the top of the rock. In this case, the river continues to move in long, sweeping curves, but is no longer actively meandering. This occurrence is called an entrenched meander because while the river still curves, it isn't moving any farther toward the outside. The best-known example of this is the Grand Canyon where the Colorado River still curves, but its path is set into the stone.

Nature