Eddies Rocks in the river bed, unless they protrude above the surface, are recognized by the nature of the turbulence downstream. During periods of low discharge, large rocks protrude well above the surface and are readily obvious from upstream. Eddies occur below both of these obstructions. An eddy is an area immediately downstream of an obstacle in a river where the current is relatively calm or may actually flow upstream. The eddy results from water filling the void behind the obstacle as the main current flows past.
Eddies provide a place for rest stops in the midst of even the most difficult rapids.
Rocks submerged just below the surface of the water can be recognized by a smooth hump that is formed by the fast-moving water as it follows the contour of the rock. This smooth hump of dark water is often followed by white turbulence downstream. Be careful since the turbulence may be several feet downstream of the rock. Such rocks are hard to spot. In slow-moving water, the hump may not show.