I am an engineer with only my FE. I have worked at a concrete dam for the past 6 years. Menos365 is correct. Every dam is different. This is my best guess from google maps, sat view. You could maybe call the utility for a more robust answer.

There are 5 tainter gates, and a single unit powerhouse. The tainter gates open from the bottom, and floating objects like trees will be caught at the surface.

Similarly, it appears the intake for the generator is far enough below the surface that trees are caught at the surface.

At our dam, we pull out equipment and remove the wood that stacks up a few times a year. 3 or 4 times in the spring, when flows are high.

It appears the turbine is a vertical shaft unit and is the south most building in the river at the dam. Ill link an annotated image after I finish this.

The only equipement we have is to detect fish tags. Like chips in pets. I am not aware of any sensor that would be able to detect a body at any stage.

Cameras. We have lots of cameras, and eyes. Thats how these situations have been discovered in the past. However, often floating objects are found along a bank before they get to our dam.

Every situation is dfferent.

Im sorry for the loss.