本计算器遵循 HEC-RAS 参考手册的方法，采用 Chow（1959）第 136 页公式 6-17（而非 6-18）计算各分区的综合 n 值。
石材护坡
如需设计护坡石材，请使用曼宁梯形渠道计算器。本计算器更适用于天然断面。
Errata
Found and fixed 23 August 2026. A segment drawn exactly vertical — two points at the same station, one above the other, which is how a rectangular channel, a box culvert or a retaining wall is drawn — added no wetted perimeter. Results from before that date are too high for any section with a vertical wall: a channel 10 wide and 5 deep was given a wetted perimeter of 10 instead of 20, and flow about 1.6 times the correct value. A sloping bank, however steep, was never affected, and neither was a wall standing above the water. If you used this page on a section with a vertical wall, please run it again.