I am evaluating a model of a lock that was overtopped during a flood event. The modeler included only one lock gate as an inline weir and used a weir coefficient of 0.5. I think it is odd that he/she did not include both gates, but I wonder if the low coefficient is meant to account for both. Does anyone know of a methodology for simplifying successive weirs to account for them as one inline weir?
That seems very low for a weir coefficient. If you are interested in getting the hydraulics at the lock itself during the overtopping event, I would suggest modeling it with two inline structures with cross sections in between.