In order to reveal the relationship between sediment deposition and precipitation and reconstruct the depositional environment of redeposit loess

the natural dam on the Loess Plateau in northern Shaanxi was chosen as the object of the study. By sampling soil cores at different sites repeatedly and sample measurement

we classified natural dam types and established the erosive sediment model of the standard natural dam in Huangtuwa by means of contrast analysis of 60-year’s rainfall data

grain size

and mathematical modeling

etc. The results are as follows: (1) Soil erosion in Huangtuwa could be better reflected when the erosive rainfall standard was set at 9.2 mm. (2) Based on the rainfall data

88.1% of the annual precipitation in Huangtuwa occurred when the average daily maximum rainfall was less than 52.7 mm

therefore

the area of “non- natural” could be determined using the sediment area resulted from a rainfall less than 52.7 mm. (3) A suitable model for Huangtuwa was established by simulating the capacity curve and setting the elevation point of the vacant capacity at 1 058.03 m

and amending the individual rainfall watershed erosion sediment transport model of Chabagou based on the fractal dimension of Huangtuwa. (4) By contrast analysis of the sediment particle size cycle law of different profiles in combination with data calculated by the model

it could be determined that the “natural dam” was closed to the dam

the “non-natural dam” was between the dam and gully

while the “non-dam” was between the gully bed and the gully head.