DSkippy

How's about floats like in a carburetor or a toilet. Have a little area that collect water possibly shaped like a an "O" with the top third cut off, so that when you break and accelerate the water wouldn't slosh out. These would will force the floats connected to the flaps closed...when it stopped, you'd have a cable to you could pull to empty them. This would provide an automated way of engaging them. If you wanted to override this feature you'd leave the stoppers opened....

Of course if you wanted to make it simple, a cable, like that of a choke, hooked to the butterfly valves on the scoop....but where's the fun in that approach....

perhaps some another complex approach could be some absorbent material that expanded when wet, that would push the valves/flaps closed when wet, as soon as they dry, they return to normal size allowing them to open...