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August, 1975 and June, 1976 (Figure 21), but just upstream erosion lowered the stream-bed slightly (.1 m) between 396 and 446. No change was noted in the remainder of the reach, from 462 to 591. It appears that previous alterations to the river have so changed conditions as to cause sufficient aggradation of the stream bed that normal water level is now above ground level along much of this reach. Ground level east of the river from 107 to 411 is below normal water level (Figure 21, Sta 381), while from 446 to 591 the fields west of the river are below normal water level. Part of the Looan River control site from 0 upstream to 152, was altered with a bulldozer in November, 1971. The only subsequent alteration was a small area in the vicinity of 76, where a cable crossing was installed, a vehicle crossing (ford) constructed and large rock placed to protect one bank from erosion. Extensive bank erosion had occurred here. From 168 upstream it has been about 30 years since any significant alteration has been done. Cross sections were surveyed in the spring of 1972, shortly after the alterations, but lack of time and funds required that only part of the transects be surveyed. Thus intervals between cross sections at some locations in this reach were greater than for other reaches. Cross sections were surveyed again in November, 1975 (Figure 22). There were no significant changes in alignment in this reach, although bank erosion and in-stream deposition and erosion did change the character of the stream in certain locations. From 0 to 137 bank erosion widened the stream an average of 2.1 m and deoosition raised the elevation of the stream bed 0.3 m (Figure 22). A hole was s~oured near the center of the channel at 152. There was considerable erosion along the west bank from 198 to 213 and downcutting lowered the stream bed an average of 0.4 m between 183 and 320 (Figure 22). There was little change in the pool between 274 and 320, but erosion on both banks widened the river as much as 5.5 m from 290 to 366 (Figure 22). Sand and Gravel Transport and Deposition Erosion exceeded deposition during each time period (Table 3 ) in Logan bulldozed. As might be expected, filling a thalweg pool on a concave bank with loose, unconsolidated sand and gravel merely provided a supply of easily erodable material for rearrangement by the river. Nearly 700 cubic meters of material was eroded from only 112 meters of stream between May and November, 1975. When combined with over 500 cubic meters of deposition in the same time period, this represents a tremendous amount of substrate and bank rearrangement (Figure 23). Stream alteration between stations 30 and 122 in April, 1975 precluded any comparison between conditions in spring 1972 and later, since no surveys were completed prior to the 1975 alteration. From station 137 upstream however, such comparisons can be made. Total erosion and net erosion exc~eded similar values in the downstream area, but when computed in proportion to length of stream involved were less per 100 meters. The disparity would be even greater if values were computed in relation to the amount of tinle over which such changes occurred. 44