I have a model where when doing the calculations the program switches from using the momentum bridge method to the energy only. It gives me the note that “momentum answer is not valid if the water surface is above the low chord or if there id weir flow. The momentum answer has been disregarded.” My issue is that I don’t understand why the program is throwing out the momentum answer. Neither the wsel or the energy elevation is above the low chord and there is not any weir flow to speak of. Just trying to understand what is going on. This happens on 25-yr flow. For reference the 10-yr flow is only 0.12 ft below but does not switch out of the momentum equation for bridge modeling, and it shows a sharp draw down through the bridge for the 25-yr event that crosses below the 10-yr and even the 5-year event. Thanks for any insight.