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mid-channel berm (1979), and after berm construction and trespass on _, National Forest lands (1986) (photographs 1,2, and 3). Photographs of the " - confluence area and South Fork San Miguel River taken in 1978 and 1986 show that the river and wetlands complex near the confluence had well-vegetated streambanks and the water level was within a couple feet of the upper banks (photographs 4 and 6). Photographs of the confluence area retaken in 1993 show the incised stream channel and lowered water table, loss of riparian vegetation and wetland areas, and unstable and eroded streambanks (photographs 5 and 7, 8-15). These off-site impacts are associated with stream channel excavation and Che corresponding change of the channel base level (gradient). Stream channel profiles or cross sections of the South Fork of the San Miguel river were .surveyed by the Forest Service in 1983, prior to initiation of an instream habitat improvement project conducted in 1984 and 1985. Three of these sites were resurveyed in April, 1993, after determining cross section locations using field notes, measurements, and photographs from the 1983 surveys. An additional site was established near the Mary E campground, within 300 feet of the confluence (Figure 1). Permanent markers for each cross section location were established on both the east and west banks. Cross section #1 and #2 are within the portion of the South Fork San Miguel that is actively eroding and headcutting. Cross sections #3 and #4 are both located upstream of the active erosion and headcutting. An understanding of the impacts to the stream channel can be gained by reviewing the base level and stream channel widths at cross sections locations over a period of time. The base level is the elevation of a given location to which upstream areas or stream reaches have adjusted (Heede, 1986). Lowering the base level, through activities such as gravel excavation, disturbs channel equilibrium and induces channel adjustment processes, such as channel incision (downcutting). The stream is then forced to adjust to the new, lower base elevation (Heede, 1980). Cross sections #1 and #2 indicate how the stream has responded to changes in the base level (elevation or gradient) of .the stream channel. High flows in 1993 caused extensive bank erosion and channel widening near the confluence (Photographs 8 and 9). Cross section #1 shows that the stream channel has widened from about 73 feet to 149 feet, and has downcut an additional 2 feet (Figure 2). This occurred between April, 1993, and August, 1993, during high flows. The channel gradient in this reach was measured as approximately 0.58 in 1983; in April, 1993, it was 2.58. The stream channel at cross section #2 has adjusted primarily by incision, resulting in the channel abandoning the previous floodplain. The channel narrowed from about"93 feet in 1983 to about 24 feet in 1993, but deepening from about 3.5 feet to almost 5,5 feet, as measured from the upper banks (Figure 3). Cross section #3 is located in a wide, formerly meandering portion of the stream channel, and I did not have adequate information from 1983 to determine if the 1993 cross section was relocated correctly. The information for cross section #3 is not included in this report.