Flume experiments are conducted to examine the effects of plan geometric factors, such as confluent planform and junction angle, on channel morphologic adjustments at stream confulences. Because a receiving stream aligns with an axis bisecting an initial angle of junction, channel morphology can be classified into three types based upon an initial confluent planform symmetrical, transitional, and asymmetrical. Channel capacity is directly related to junction angle regardless of confluent planform. However, changes in channel slope and form ratio are different depending on confluent planform. They are related to junction angle inversely for asymmetrical confluences, but directly for symmetrical confluences. It indicates a mutual adjustment of channel slope and form to exogenous conditions. Channel morphologic adjustments to the changes of junction angle (A) and symmetrical degree of confluent planform (S) can be explained in terms of combined effects of these variables as follows :
A+S+≈c+ (w+d-) f+s+
A-S+≈c- (w-d+) f-s-
A+S-≈c+ (w-d+) f-s-
A-S-≈c- (w+d-) f+s+
where c is the channel capacity, f the form ratio of width (w) to depth (d), and s the channel slope. The plus and minus superscripts represent an increase and decrease in channel characteristics. These relations qualitatively show how changes of channel characteristics occur with the plan geometric factors at stream confluences.
