There are two ways to look at a similar process.
If Normal pool is the present drain setting then raising the height of drain makes for a flood pool. Conversely, lowering the height of the drain makes for a drawdown pool. So if you delayed raising the water level until spring you might still have opportunity for cool season growth along the bank before flooding. Under this scenario you wouldn't be concentrating BG until next fall when you drop the water level to "normal pool". Also, this scenario still preserves your existing water level, however, you would only get the benefit of flooding if the rain comes.
