When performing scour computations for a bridge under flow condtions that are not overtopping be bridge but that do produce an HGL that falls between the minimum top of deck and maximum low chord elevation, how should the flow area, width and hydraulic depth be calculated. I am finding that the hydraulic properties table will often leave these values blank for this type of condition. Would the overbank width be the left over bank bridge opening length and would the area include all the way up to the HGL for the limits of the bridge opening? I’m confused about selecting the correct contraction scour parameters Yo and W2 for submerged bridge scenarios.
Any feedback is appreciated.
Thanks