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I am curious about 2D modeling of bridge piers when the 2D cell size is small enough to appropriately model the individual piers. I have been using a grid cell of 1m or less. There are many bridge crossings in this stretch of river, and most of the piers are about the same width as my grid cells so I can model the piers as blocked cells using a Z polygon or Z line. The results seem to accurately capture changes in velocity patterns adjacent to the piers. I've attached an image of results through one bridge. My question is this: is it necessary to add additional form losses if the piers are modeled as blocked cells, or will this accurately estimate losses around the piers? (Assume all flow is below the low chord). If additional losses are necessary, is there an appropriate way to estimate these? Presumably this would be smaller than the form loss used for a percent blockage (which wouldn't account for these velocity patterns). I am using a 1D HEC-RAS model as well, but the 1D bridge modeling is producing some contradictory results depending on which bridge modeling method is used (either energy or momentum equations). I was hoping the Tuflow model results could provide some support for one method or the other. -Frances