ryan hall specifically mentioned that area due to the mountain range and that it was about to get a massive amount of rain and even recommended people get out, this was about least 2 days before landfall. that livestream isn't listed though, only his livestream of hurricane day and after. it's the first time i watched him, but he specifically called out that area for massive rainfall, flooding and landslides. if he could tell that from basic weather data models, then it was probably known to the authorities. however, they may not have been able to do much about the dams as this anon said    , but they could have warned the population of the upcoming threats better.
United States