陡坡河道洪水过程中常伴有强烈的泥沙输移，导致河道行洪断面缩小及水位的异常激增，但洪水过后泥沙往往被冲刷输往下游，在河道中难以发现泥沙的踪迹。泥沙造成洪水漫溢仅在洪水过程中发生作用，使得人们通常认为洪水发生的根源是强降雨，而忽略了泥沙的附加致灾作用。为了探索泥沙在洪水灾害中的影响，本文在变坡水槽中研究了在上游来沙量突变为零时床面前期淤积泥沙的冲刷发展及水位变化规律，解释了非超标洪水条件下，河道洪水位畸高而又未见明显的断面萎缩异常灾害的现象，探明了泥沙与洪水灾害的因果联系。试验结果表明上游来流量、加沙强度和泥沙粒径越大，冲刷水深越大。上游来流量、加沙强度和河床比降越大、泥沙粒径越小，冲刷速度越快。

During the flood process of steep slope，strong sediment transportation often leads to the reduction of river flood section and the abnormal increase of the water level． However，after the flood，the sediment is often washed down to the downstream，it is difficult to find traces of sediment in the river． The flood overflow caused by the sediment only plays a role in the flood process，which makes people generally think that the root of flood is heavy rainfall，but neglect the additional disaster－causing action of the sediment． For the purpose of exploring the influence of sediment in the flood disaster，the scouring development and water level variation of silt at the early stage of the bed are studied in the variable slope flume in this paper which explains the phenomenon that under the condition of non－exceeding flood，the flood level of the river is abnormally high while there is no obvious unusual disaster of section shrinkage and emphasize the causal link between sediment and flood disaster． The result shows that the larger the flow volume，the strength of sand and the particle size of sediment，the greater the scour depth． The larger the upstream flow，the intensity of sand and the ratio，the smaller the particle size of the sand，the greater the scour speed．