From 4m36s of https://youtu.be/N70t8hQCcPI?t=276, the speaker says
ゴミがたくさん流されてきました
This apparently translates to "A lot of trashed was washed up."
My question is why 流す is being used here instead of 流れる? 流れる is an intransitive verb, and here the subject of the sentence is "trash". So wouldn't that be the better choice?
On the other hand, 流す is transitive. So we're expecting the subject to act upon some object (を). But here the subject of the sentence is ゴミ, which isn't acting upon anything in the sentence (no を marked nouns).