Based on the analyses of the test results of the rigid longitudinal booms on a model on Dashaba of the Jinsha River and the data obtained through the investigation on the spot, this paper puts forward some new ideas about the effects of the discontinuous water flow surface on rigid longitudinal booms.The discontinuous water flow surface caused by the salient bank makes the log stack move away from the boom and thus reduces the load of the boom notably. This paper suggests that further researches of the effect of the discontinuous water flow surface on rigid longitudinal booms and stacks should be carried on by using fluid mechanics principles.