Abstract:In order to clarify the flood infiltration process in the uncontrolled engineering area, and improve the ability of flood prevention and control and the degree of flood resource utilization, the hyper-concentrated flow channel downstream of the Xitugou watershed in Yangguan, Dunhuang was selected. The field experiment and laboratory analysis were conducted to measure the different pressure heads of the river section from the upper section to the lower section of the river. Under the infiltration rate, the saturated infiltration coefficient was obtained by fitting, and the saturated infiltration coefficients at different depths were obtained by laboratory measurements. The variation of saturated infiltration coefficients of the left and right banks, centers and different depths of the riverbed was analyzed. The results showed that the saturated infiltration coefficients:upper section (0.003 1 cm/s) > middle section (0.002 9 cm/s) > lower section (0.002 6 cm/s); the saturated infiltration coefficient at different depths in the upper part was larger than that in the middle and lower sections, and the difference between the middle and lower sections was small. On the whole, the saturated infiltration coefficients on both sides of the riverbed increased with the increase of depth, and the saturated infiltration coefficients of the riverbed decreased with the increase of depth. The reason for the above results was that the sediments were deposited along the hyper-concentrated flood, the coarse sediments were deposited first, and then the fine sediments were deposited, resulting in the difference in porosity of the upper and lower sediments, and the variation of saturated infiltration coefficients in river sections and different depths. The infiltration rate was determined by different pressure heads to characterize the infiltration rate under different flood levels, the trend fitting showed that the surface infiltration rate increased linearly with the increase of flood water level.