Riffle

A riffle is an important component of a river or a stream's physical morphology and a fly fisher must read these areas carefully because of the abundant aquatic life they are able to support.

The anatomy of a riffle is quite straight forward and easily recognized. Riffles are generally higher energy sections of a stream or river system and tend run at shallower depths than other portions of the system. Because the energy level of the water passing through a riffle is higher than average for the system, larger cobbles, rocks, and stones often collect along the river bed beneath a passing riffle. The length of a riffle is primarily determined by the gradient of the stream and riffles can be very short (only a few meters in length) or extremely long (several hundred meters in length). Riffles are classically located just up stream from deeper pools, slower runs, and otherwise undefined or smooth water areas.

Riffles are so important to fly fishers -- especially to trout and steelhead anglers -- because of the aquatic life they are able to support. Many aquatic insect species spend much of their life cycles enjoying the cool, oxygen rich environment a riffle provides. The shallow water in a riffle also offers these insects and the plants on which the often feed the sunlight necessary to thrive.

Because riffles often include whatever happens to be caught in the main drift, they can be thought of as a conveyor belt potentially filled with morsels of food for hungry fish. Trout and steelhead will commonly park themselves in the middle of this efficient feeding lane and feast on these insects and often call riffles home.

When fly fishing, it's always important to approach a potential holding area for fish with great care and attention to sound, light, shadow, and other disturbances -- if any of these environmental elements is out of balance, an angler will greatly increase the chance of spooking wary fish. However, in when approaching a riffle, an angler can usually afford to be a bit more conspicuous on her approach due to the good cover a riffle offers a holding fish. Look for choppy areas, contrasting currents that create nice seam lines, dips, and rises above rocks -- these are generally the most productive angling spots within a riffle.