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Although an unknown amount of channel alteration had occurred here some- time over 20-30 years ago, this reach (Figure 1) was selected as our primary control site since it was the most IItypicalll site on either river with natural conditions (Figure 9). This site contained much streambank vegetation which provided the stable undercut banks and overhanging cover that is required by brown trout, a key species in these rivers. Pools and riffles occurred alter- nately throughout the entire reach. Blacksmith Fork River Recently Dredged Site Gravel that was deposited at a sharp bend of this river formed a IIdamll that created flooding problems for a local landowner. This landowner informed us that he was going to remove the gravel from the stream bottom, which gave us the opportunity to survey the entire reach before it was altered (Figure 1). This reach was altered for approximately 520 meters by backhoe on March 20 and 21, 1975 when the gravel was removed from the stream bottom and deposited on the streambanks (Figure 10). The backhoe was usually operated from one bank so that little change occurred to the opposite bank and there was minimal reduction in stream meander or sinuosity. Much of the gravel was redeposited in this reach during the spring runoff so the reach was dredged again by the landowner on August 28, 1975. This site was studied intensively since we were able to survey the reach before alterations were made, it contained a good pool-riffle ratio, and had good streambank cover. Estimates of the fish population were made before and after the reach was dredged, before and after spring runoff, and during selected conditions such as low streamflows to docu- ment the responses of the fish to various physical conditions. Blacksmith Fork River Recently Bulldozed Site The flood plain of the Blacksmith Fork River as it meanders through Mill- ville, Providence and Nibley, Utah and adjacent areas is being converted from agricultural uses to commercial and residential uses (Corps of Engineers 1976). In3May 1971, the streamflow of the Blacksmith Fork River was 23.4 m3/sec (825 ft /sec), a level exceeded only by the historical record of 45.9 m3/sec (1,620 ft3/ sec) of t1ay 1917. The Corps of Engi neers channel ed a reach of the Bl ack- smith Fork River near Nibley and Millville, Utah in the Fall of 1971 as a measure to prevent future flood damage in this area. On September 6, 1975, the landowners rechanneled a part of this reach (about 300 meters) by bulldozer (Figure 11). This site (Figure 1) was chosen because it provided an opportunity to compare the effects of an old bulldozed with a recently bulldozed reach. This site was subdivided into a recently bulldozed portion (1975) and an old bulldozed section (1971) immediately upstream. Logan River Control Site This reach (Figure 1) was chosen to provide supplementary information to the primary control site on the Blacksmith Fork River. This reach did not contain conditions as natural as the primary control site, but the information from this site on the larger river - the Logan - could be compared with similar data from the more intensively studied site on the smaller Blacksmith Fork River. This reach was altered several times in the past, most recently about 30 years ago, but is believed to be relatively stable now. Because of the 11