The flood resulting from a dam breaking,and opening by break very spillway,and in order to guarantee safe enlarging the outflow of reservoir,spreads quickly and often causes catastrophes.

• 大坝溃决造成的洪水、以破坏方式开启非常溢洪道造成的洪水以及为保证大坝安全加大水库放流形成的洪水，传播速度快，破坏性巨大。