The researchers studied how tides move in the Lower Fraser River in British Columbia, Canada. They used water level data and a computer model to see how tides change from the mouth of the river to upstream areas. They found that tidal amplitudes decrease as you go upstream, with lower amplitudes in high flow seasons compared to low flow seasons. The Pitt River and Pitt Lake system is important for how tides move in the river. The balance between pressure and friction controls the momentum of the river water. The interaction between the river and tides affects how fast the water flows downstream.