Least-Cost and Most Efficient Channel Cross Sections

It has been a long-standing concern to decide if a channel should be designed to have the highest hydraulic efficiency or the least cost. In this study, a large amount of channel construction costs were reviewed and analyzed to derive the channel construction cost function as the sum of the costs for the land acquisition of the channel’s alignment, lining material for the channel’s cross section, and earth excavation for the channel’s depth. Case studies conducted in this technical note indicate that the differences between the least-cost and most efficient cross sections are closely related to the channel lining to land acquisition cost ratio. When the lining to land unit cost ratio vanishes, the difference between these two cross sections is diminished. As revealed by the cost data, the least-cost channel section tends to be deeper if the land cost is much higher than the lining cost. This trade-off was incorporated into the normalized equation to provide direct solutions to the least-cost channel cross section. The normalization of the least-cost equations allows this approach to be transferred to other regions when the local cost data are available.