The Coquille River is a tidal-effect river. During high tides at sea, the water at the mouth of the river acts like a dam, impeding the flow of the stream. More water always flows out into the ocean than enters with the tide; however, logs, sticks, and leaves on the surface can float upriver at certain times of day. There is a time lag between the high tide at sea and the effect pushing upstream. This varies according to the number of miles from the ocean. The tidal-effect is observed as far as Myrtle Point, some upriver. The head of tide is upriver from the mouth at Bandon. But some salt water does enter across the bar. The salt water intrusion was once minor. Today, however, sometimes traces of salinity appear only a few miles below the town of Coquille. This phenomenon affects industry along the river, as mills and other sites need fresh water intakes on the river in order not to rust or damage equipment or affect production processes.