From the looks of they could have stood on the causeway and plucked debris out of the water with hooks and other implements

And used small riverboats/bass boats to get up close to particularly large pieces of debris and hook up tow cables.

Presumably there must have been a reason they couldn’t. But I doubt it was because such a task in of itself would have been considered unsafe. Perhaps some extenuating circumstances not directly related to the task would have rendered it unsafe I guess?

I mean hell. Even deploying upstream and catching debris as it came down could have potentially worked. And reduced any potential safety risk of setting up near/on the Dam.