Introduction A river or stream is dynamic through time. Change is one of the most common features associated with river and stream channels. In general, this change is very slow, however, and only over long periods of time is it actually noticeable to most individuals. As a result, engineers, ecologists, and others involved with the hydrologic balance of a stream many times treat the stream system as static (i.e. unchanging in shape, slope, or pattern). One only has to observe a favorite fishing stream or pleasure area along a stream to notice that the stream channel itself probably looks slightly different now than it did two or three years previous. In general, most streams are continually changing position and shape as a consequence of hydraulic forces acting on their beds and banks. This stress is mainly a result of climatic changes from year to year in the amount of water flow variation that occurs in the stream. Over time, the stream system adjusts to this natural variation in flow and develops a pattern which puts the system in a quasi-steady, yet dynamic, situation where only unusual climatic events or human activities may cause rapid changes in the nature of the stream channel morphology (dimensions, shape, or pattern). It should be noted, however, that streams are, in fact, the most actively changing of all geomorphic forms, especially alluvial stream systems. It is the rule rather than the exception that banks will erode, sediments will be deposited, and floodplains, islands, etc., will undergo change with time (Richardson et al. 1975). The problem in all this comes when humans induce change upon the system without taking the necessary steps to restore the quasi-steady situation and thus set in motion a response by the stream system to adjust to this change, which results in the propagated response along great distances from the human-induced action.
In planning and designing stream channel restoration and stream system balance, it is critically important to avoid the geometric stress thresholds of a stream at which dramatic and significant undesirable landscape modifications occur. It is desirable to approximate a range of appropriate stream channel features that will cause the stream system to respond to its natural inclinations (the stream pattern which would exist under normal conditions) as if no human action had occurred. This intervention will result in controlled sediment production and produce a channel similar to the existing stream channel. The end result will be a system where stream habitat should be equivalent to predisturbance and, hopefully, a slight enhancement of habitat and form.
This chapter discusses methods and techniques for restoring a stream channel to its natural inclinations after a human-induced change such as surface mining, road construction, etc. The main emphasis will be on meander parameters and their importance in stream channel stability.
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