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400 :J: Vl 300 - I.L. I.L. 0 ?OO 0:: u.J a:l 100 :::: :::l z: 0 1962 63 64 65 Pre-logging 66 67 68 69 70 71 Post-logging 73 72 Figure 1. The effect of logging on coastal cutthroat trout populations in Needle Branch, Alsea River Watershed, Oregon. (From Lantz 1976). western rangelands (Buckhouse 1977). How- ever, the deleterious effects of grazing on aquatic ecosystems and riparian vegeta- tion has been recognized in a number of papers (Behnke 1977; Duff 1977; Gunderson 1968; Kimbal and Savage 1977; Lorz 1974; Platts and Meehan 1977). Quantitative data on the effects of livestock grazing on a population of brown trout (Salmo trutta) was presented in the special reP9rt by Mar- cuson (1977). His major findings on the trout population in natural versus grazed reaches of Rock Creek, Montana in 1969 are summarized in Fig. 2. The r.wnber of trout was 268% greater and the biomass was 336% greater in a natural reach of Rock Creek when compared with a reach that was grazed by livestock. The differences in the brown trout population in grazed and natural rea- ches of the same Montana stream were not as large in 1964-65 (Gunderson 1968). Marcu- son (1977) pointed out that the streamflows were higher than normal during Gunderson's study and these flows contributed water to overflow channels that produced lower val- ues for the trout population in the natural reach. Lorz (1974) reported higher brown trout populations in grazed reaches of the Deschutes River, Oregon, than in natural reaches. However, he pointed out that the trout populations were closely correlated with willow cover along the streambank and, with increased streamflow, the grazed reaches provided more habitat for the trout as extensive willow cover on the banks was flooded. Behnke (1977) believed that the rehabilitation of streams that have been damaged from livestock grazing "offers the single greatest potential to increase the abundance of wild, self-sustaining trout populations in the western U.S.". Live- stock grazing can have adverse effects on the morphology of the stream channel, stream- flow, water temperature, water quality (par- ticularly sedimentation), soil stability, and the abundance and biomass of inverte- brates and fish (Platts and Meehan 1977). Channelization Natural streams tend to form a repeat- inq pattern of curves or meanders that are a function of streamflow, channel geometry, channel slope, geology, bank stability, and streambed stability (Lang 1971a; Leopold and Langbein 1966; Tinkler 1970). Stream meander forms a ratio between the wave length of the curve and the l~ngth of the ch~nnel that usually ranges between 1.3:1 and 4:1 (Leopold and Langbein 1966). Since stream meanders often interfere with the activities of man, stream channels have been straightened for highway construction, land reclamation, navigation, flood control, and for other reasons. In Montana, activi- ties associated with agriculture, railroads, and roads accounted for nearly 90% of stream alterations (Fig. 3; Peters and Alvord 1964). Mining activities in Idaho caused 13% of the alterations to s~ream channels in that state (Gebhards 1970). Straightening and reducing the length of the original stream channel increases the hydraulic gradient. Cover along the streambanks is also removed and pools are often converted into riffles or runs (Elser 1968). Instable substrates fol- lowing channelization are believed to be the most significant factor related to changes in fish and invertebrate populations (Etnier 1972). Stream channelization is a subversive approach to controlling high wa- ter since it generally aggravates flooding downstream (Campbell et al. 1972; Stroud 59