Wow I go to work for a day and all this happens. I have several things to say but I don't know where to start so I will make it simple.
1) During the course of this thread I was attempting to explain things in a manner that someone with a nontechnical background could understand. I hesitated to mention Hydraulic Grade line but I felt I had to in order explain some of the concepts. I really did not want to get into the details of how the computer programs work and the theory behind it as I don't think it could be understood by all. I did not want to mention variable roughness coefficients, hydraulic radius, wetted perimeter, energy grade lines etc etc. Not to mention raising a number to the 2/3 power. In addition trying to explain what a flood stage is, whether a river is in or out of it's banks or even keeping track of whether a station has a local zero or is referenced to NAVD88 and is adjusted to the latest GEOID.
2) Mr. King I wouldn't be going anywhere to apply for a job as a river hydraulicists. I suggest you do a Google search for "HEC RAS" (Hydraulic Engineering Center - River Analysis System) and download the manual. Study that manual and EDUCATE YOURSELF so you can start to get a grasp of the intricacies of what is going on here. Because, by your posts today, I can see that you really don't know ------- you really really really don't know. Don't ask me to explain it either, because the concepts that are presented in the manual are taught in the Senior year of most Civil Engineering Schools. And why is that --- because you will need every bit of mathematics, physics and concepts taught in lower level engineering courses in the three previous years to fully grasp the situation. Then you will have to work at it for several years for it to really mature in your mind and be confident enough to make sound engineering judgements. I can assure you that the Corps of Engineers DOES NOT make their decisions on river stages alone and they use many more decision making tools than could be listed here - including sound engineering judgements.
Dominique D. Naomi, P.E.