Many water surface profile software programs prior to HEC-RAS had a quirky rule against having perfect vertical sides. In other words, you could not have two or more elevations at the same stationing. A perfect example of this is a rectangular flume. The workaround for the older software was to define the tops of the flume to be 0.01 ft or meters just outside of the bottom edge of the flume, like this:
In HEC-RAS, you don’t need to do this. In fact, you shouldn’t do this as you’ll get the wrong answer. Let me explain why...
