The definition of "down" is given by Newton's laws on gravity, it's the direction towards the center of the globe, no matter the position of the globe. Hence a river originating at some high mountain and flowing towards the ocean will run "down" all the way even if the elevation of the mountain seems insignificant compared with the earths curvature.
The Coriolis forces are well-studied and well-understood and can be directly observed in weather patterns and ocean currents.
Contrary to popular belief, the Coriolis effect has very little to do with the vortexes formed when flushing the bathtub.
The mysterious Coriolis forces seem to eat much more force than they expel. This is one of my main logical hurdles with a 1000mph spinning atmosphere.
Also if the rotation causes tidal currents in the ocean, I would expect rivers & lakes to be affected by the spin as well, but nada.
Streams on Mountains running downhill make perfect sense to me on a plane. Streams on mountains on spinning balls where gravity overcomes curvature but the spin has no effect on the stream, makes very little sense to me
Rivers and lakes also experience the same forces as the sea, but the coriolis forces are very week on smaller scales.
Tides and tidal currents are (in my world paradigm) caused by the moon and has nothing to do with the coreolis effect. (And the tidal energy is not magically created, eventually the moon is falling down due to the tidal forces).
The Coriolis seems to be a selective magical force. Sometimes it explains a little tiny affect compared to the huge forces going on, sometimes it explains zero affect, despite constant forces.
The moon, like the Coriolis has selective affect on water. Lakes are completely unaffected by the moon, as are lakes completely unaffected by the supposed Coriolis forces. Same with every river & stream I’ve seen. My logic doesn’t allow me to believe in magical Coriolis. I’ve read dozens of supposed definitions & seen countless examples attempting to demonstrate & or prove the Coriolis & I see many many contradictions & missing affects.
My astronomy teacher back in 2000 was convinced we were losing the moon slowly. Seems many theoretical theories change over just a few decades. I used to think the evolution of knowledge was really interesting. Now it looks like mathematical ass covering
According to https://oceanservice.noaa.gov/facts/gltides.html there is a 5 cm difference in the great lakes due to true tidal forces.
It's not "selective", it's just about size and mass. All the water in the great lakes is like a drop compared to all the water in the world oceans.
Distance is also very much relevant. The water doesn't grow or shrink, the sea is rising somewhere while it's ebbing somewhere else. Tides are there because the moons gravity force on the water is different at different places on the earth. It's not so much of a difference at different points of the great lakes. Same goes with the Coreolis effect. Of course it acts on rivers as well, but what do you expect from a small force acting on a river? The force pulling it down to the sea is much stronger.
Any astronomy teacher teaching that the moon is disappearing into space should find another job, even if it was 18 years ago. The moon is getting clsoer to the earth over time, and this has been known for at least a century if not three.