I've actually done controlled burns in Northern BC back when I was in forestry. We go in during the winter and burn up dead branches that have fallen during the year. The snow stops the fire from spreading and the burning depletes the excess fuel on the ground, making it harder for fires to grow out of control in the summer. The burning also releases nutrients into the soil and encourages a healthy undergrowth by making space for new plants.

As others have mentioned there are also some trees(usually pine) that require fire to spread seeds. Those controlled burns are usually reserved for public parks where they want the forests to have a more natural look. They are small fires created with drip torches, just enough for the cones to open before being put out. When mass producing those pines trees to replant a logged forest, we use ovens to open the cones instead.

Controlled flooding is also very much a thing we do as humans either to divert water from flooding other areas, or to rehabilitate soil. Its pretty common throughout the world. I would bet that you are unfamiliar with the practice because you live somewhere beavers are already doing it for free.