1) Boarding 2) Flashboarding 1) Flash boarding 
• (n.) A board placed temporarily upon a milldam, to raise the water in the pond above its usual level; a flushboard.
Flash'board` noun A board placed temporarily upon a milldam, to raise the water in the pond above its usual level; a flushboard. [ U.S.]
[n] - boarding place along the top of a dam to increase its height
flashboarding noun boarding place along the top of a dam to increase its height
a board, or one of a series of boards, as on a milldam, used to increase the depth of the impounded water.