I wouldn't have any growth around a dam or spillway. Other than that, I prefer to leave trees all along the shore, trim up the lower branches as high as you can reach. If you have a lot of trees, take out anything smaller than 4 inches in diameter. Trees near the water will provide shade to both fish and fishermen. You can always cut down more over time, but you can't stand them back up once the damage is done. They also make excellent posts for outdoor lighting.