Dynamic change of hill slope and gully erosion in typical area of black soil region during the past 40 years

It has significant theoretical and practical value to conduct the research on dynamics of hill slope and gully erosion for better understanding soil erosion process and drawing up protection measures in the black soil area of Northeast China. In this paper, taking eastern Kebai black soil area as an example, high resolution satellite images, including the Corona spy satellite images of 1965 and Spot-5 images of 2005, were used to extract two periods of information such as gullies, vegetation, land use, etc. The spatial data of terrain, precipitation and soil, as well as the attracted data from the images were used to develop a hill slop erosion model based on the framework of universal soil loss equation (USLE). Thereafter, the hill slope and gully erosion dynamics during the past 40 years was analyzed. The results showed that hill slope erosion in this area was dominated by light erosion grade. The area of moderate and heavy erosion grades only occupied a small portion. Although the total area of hill slope erosion changed just a little, the change of hill slope erosion grade varied from place to place. The number of gullies in the study area increased from 1 682 in 1965 to 2 561 in 2005. Farmland area was swallowed by growing gullies at a speed of 5.23 hm2 each year. The ratio of hill slope erosion and gully erosion was approximately 3.5:1, suggesting that the sediment mainly came from the hill slope. The research result could provide a scientific basis for controlling water and soil loss in black soil area of Northeast China.