Abstract: A full-loaded river frequently produces in wet season high peak discharge flow that carries a quite large amount of sediments. Such flow often causes very strong erosion on the river bottom during flood rising, since its behavior is different from ordinary silt carrying flow. Great probability of the erosion arising leads design buried depth to become one of important design parameters for long distance pipeline works to cut through the river in safety. However, the calculation about the scouring has still followed the design standard-"64-1" formula which was established in 1960's for the common circumstance of erosion. This paper, taking the distinguishing feature of hyperconcentration flood into account, deduced approach to computing probable maximum eroded depth and studied the existing common calculations (including "64-1" formula) both in theoretical and practical cases as well. The conclusions drawn from the study are that "64-1" formula does not apply to the case of hyperconcentration flood and the Zhang Ruijing's initial velocity based approach which was proposed in this paper can fit the practical case well.