Channel & Overbank Transition Option

When the abutment has no setback (is at the channel bank), the scour at the overbank will be equal to that for channel. When the setback is small, the scour at the overbank will be very close to the scour in the channel. However, due to the idealization of channel and overbank flow into rectangular shapes, the calculated overbank scour may be based on clear water scour (as determined from the Approach Section calculations) when it is actually subject to live bed scour conditions from the main channel. There is obviously a transition zone between the no setback case and the long setback case. To make a smooth transition, the following scheme is used to calculate the scour in this transition zone. This scheme applies to both contraction scour and abutment scour, although the details are somewhat different. The program provides this option to disable this interpolation. In case of armored overbank and vegetation covered overbank, user should choose to disable this interpolation.