Laserfiche WebLink
<br />restored the number and amount of deep pools, it actually increased both (See <br />values for June). The number and size of the pools did not change much during <br />1976, probably because of the low runoff. <br /> <br />Table 1. Changes in the number and total linear meters of pools more than one <br />meter deep in a dredge~ reach of the Blacksmith Fork River, Cache <br />County, Utah, 1975-76. <br /> <br /> 1975 1976 <br />Parameter Jan Apr Jun Sep Jan Apr Jun <br />Number of Pools 5 2 8 2 3 5 4 <br />Total linear meters 128 34 158 64 73 70 73 <br />lOredging of this reach was done by backhoe in 1 ate March and late August, 1975. <br /> <br />Certain pools were restored by the spring runoff after one or both dredg- <br />ings (Table 2), while one (390) was not eliminated by either dredging, but <br />gradually decreased in size until it disappeared. <br /> <br />There was little change in the stream course at Blacksmith control so <br />meander and centerline length were unchanged (Figure 14). Changes in stream <br />bottom elevation were minor, leaving current flow and gravel bars relatively <br />unchanged. The number of pools more than one meter deep decreased because of <br />the decreased flow rather than any changes in the stream bottom. <br /> <br />Alterations in September at the Blacksmith bulldozed site resulted in <br />reduction of some meandering, changing the thalweg to center length ratio from <br />1.05 to 1.01. This ratio had changed to 1.02 by June, 1976 (Figure 15). <br /> <br />In August, 1975, prior to alterations, there were four pools more than 1 <br />m deep in the area of alterations. All of these pools were filled in by the <br />bulldozer. Three of the four pools had been scoured out and restored by spring <br />runoff as of June, 1976. <br /> <br />Overall there was little change in alignment at Logan control, with the <br />thalweg/centerline length ratio changing slightly from 1.006 to 1.01. There <br />were changes in elevation of the stream bottom ranging from -0.7 m to +0.5 m, <br />indicating possible changes in current velocity. Gravel bars, which were a <br />prominant feature in some locations in late 1972 and in 1973, had apparently <br />been rearranged by November, 1975, and were less numerous and prominant. Pools <br />greater than one meter deep increased from one in 1972 to four in 1975 (Figure <br />16) . <br /> <br />Changes in Cross Section with Time <br /> <br />With 0.42 m of fall per 100 m, the stream bed gradient at Logan River old <br />bulldozed is the lowest of the study sites. This reach was channelized in <br /> <br />24 <br />