#Riffle run pool series

Additionally, some fish and insect species reproduce or grow within riffles. This fact is the reason different species of fish like idling near riffles especially in hot weather. Because of the turbulent nature of riffles, plenty of air gets mixed up with water providing aquatic animals (fish and insects) with the much-needed dissolved oxygen. Daters, sculpins, and crayfish hide beneath sediments at night enabling predators like Strout to easily find and feed on them. For these species, riffles may also provide food deposits hidden under the rocks, as well as shelter. The rocky bottoms of riffles provide some species of fish like trout with good spaces to hide away from predators. Stoneflies and caddisflies get good cobbly gravel within riffles to hide. Such fish and other organisms include mayflies, stoneflies, caddisflies, Strout, net-winged midges, sculpins, and dace. Within these features, only fish with a capability of clinging to rocks may exist for short periods of time. Riffles have a narrow aquatic plant and animal life and in some cases, plant life is limited to small algae and diatoms. Because the water deposits sediments on these features, the discharge from the riffles usually has fewer sediments. Some sediments may be exposed to the water surface and some may be submerged near the surface. During the development process of features in a stream, riffles normally develop long before the streams form visible meanders, and continues to develop even after the meanders form. In many circumstances, riffles are features of cold water streams and vary in depth, usually between one inch to approximately three feet. Once in a while, heavy stream flooding may alter the riffle-pool sequence but it takes a short period to redevelop.

#Riffle run pool series

Eventually, the stream develops a series of riffles and pools. As the water flows faster over a riffle, it forms a pool at some distance after the riffle which may become bigger over time. As the stream continues to deposit the particles, they cause a disturbance in the flow thus making water flowing above them flow faster and in a more agitated manner than upstream and downstream. Since the streams carry the rock and gravel sediments over a short distance, they tend to be rough and different from alluvium.

Formation of RifflesĪs a stream flows, it carries rough sediments downstream which it deposits in shallower areas. Just like other river features, riffles have their advantages and disadvantages to aquatic life within them. In most cases, a pool forms immediately after a riffle thus forming a sequence of riffle-pool features on a given length of a stream. Mostly, riffles form in the shallow straight waters between loops. A riffle is a shallow landform (elevated river bed) on a stream where water runs fast and in an agitated manner due to sediment deposits below the place. Rivers form a variety of features that vary in size and functions as they flow.