Effects of channel enlargement by river ice processes on bankfull discharge in Alberta, Canada

Results from 24 rivers studied in Alberta show that bankfull recurrence intervals average 16.7 yr, ranging between 2.4 and 45 yr. These results differ sharply from the average of 1.6 yr for rivers in the warmer countries such as Great Britain, Australia, and the United States. The difference in frequency of return period for Alberta rivers may be attributed to channel enlargement caused by the occurrences of scour from ice breakup, drives, and jams of unknown frequencies. The enlarged channel areas (cross sections) at bankfull average 2.6 times larger, but due to comparison adjustments, may be 3 times larger than comparable rivers at bankfull in the United States, and are thus able to carry an average of 4.7 times more discharge, taking into account the increase in velocity.