I should have said brain to size ratio, an elephant has a huge brain to size ratio compared to a triceratops but I've not seen anything to indicate either built dams with any intent or future planning. Beaver do how ever build dams specifically to make their lives better, whether or not they actually have the future in mind is debatable.
The phrasing of the OP indicated some intent to build a dam not accidentally dam up a stream.
Are you suggesting that triceratops pushed down trees with the intent to dam up a stream?
I am not saying this is a hoax, people mistakenly attribute intent to things all the time without justification but not to intentionally mislead.
I'm not sure why you brought this up but dimetrodon was a synapsid like you and me, triceratops and every other dinosaur were diapsids like crocodiles, lizards and birds.