I am working on a model with an entrenched river at the bottom of a valley. I am spanning the valley with the proposed bridge. The proposed bridge has 2 piers located in the upper floodplain of the river. The WSE is way below the bridge low chord and there is no bridge constriction. The flow is subcritical and remains as such thought the model. The two piers are 2.5 ft diameter. When I run the proposed model, I get a very small reduction in the WSE. This seems counterintuitive. Any ideas on what is causing this reduction? Thanks