Bridges
The option to choose for bridges whether building or ground height is taken into account. ground height is the standard, which can be adjusted via advanced settings. This is to avoid unrealistic adjustments to the flow underneath bridges.
Documentation:
https://support.tygron.com/wiki/Include_bridge_elevation_(Water_Overlay)
https://support.tygron.com/wiki/How_to_remove_bridge_heights_(Water_Overlay)