Tides + Temperature + Rocks
Rivers are always moving- flowing towards the sea.
Near the coast, the tides add extra action. Twice a day the tides change the level of the water in the river dramatically. Twice a day the river's level rises by several inches to a foot, and twice a day it falls again, as the volume of water is pulled and pushed by the moon's gravity.
When it's cold enough, it gets really interesting.
A few inches at the surface may freeze during a lull at high tide, while the river keeps rushing below it. When the tide goes back out, the water underneath can abandon the frozen sections it had been supporting, forcing them to be lowered onto rocky surfaces. Or the moving river can drag frozen sheets with it, like panes of glass cracking and crashing against rocks and frozen banks.
Sometimes frozen white chunks are just left politely on a lawn next to the river as the tide travels out to sea.
The sound can be surprising! Sometimes creaking, or tinkling ethereally, sometimes booming. Always beautiful.
