Multiple outlets describe how coastal ocean tides can move upstream along rivers, forming “tidal rivers” that can extend hundreds of kilometers inland. In these stretches, river water and the incoming tidal oscillations interact in complex ways. When a river is already experiencing high discharge or flooding, the tidal influence can further raise water levels rather than simply displacing or draining flow. This added effect can increase the river’s overall peak height, making flooding more severe than it would be without tidal forcing. Phys.org highlights that tides push upstream and that this interaction can amplify peak water levels during flood events. Eos (AGU Earth Science) adds that specific tide–river mechanisms, including tidal subharmonics, can contribute to higher water levels in tidal rivers. Together, the sources emphasize that flood risk in tidal rivers depends not only on upstream rainfall and river discharge, but also on timing and characteristics of ocean tides, which can produce additional amplification of water levels during flooding.