Gully Characteristics And Its Affecting Factors In Heilongjiang Province, China

Research of erosion gully distribution characteristics and its affecting factors have significant meanings to preserve black soil resources and guarantee national food security. Based on field sampling investigation and remote sensing image interpretation, and taking ArcGIS as the platform, this paper analyzed the distribution characteristics of erosion gully in Heilongjiang province, and discussed the impacts of rainfall characteristic index and land use, and analyzed the distribution characteristics of erosion gully in different geomorphic region and erosion pattern area. And the study classified the management urgency level of erosion gully which take gully density as indicator finally. The main conclusions of the paper as follwing:(1) Total of 115516 erosion gullies in Heilongjiang province. The bumber of erosion gully in puberty was greater than erosion gully in stable stage. The bumber of erosion gully in puberty account 86.3% to total erosion gullies, and the bumber of erosion gully in stable stage account to 13.7%. The length erosion gully in puberty is mainly distributed in 100-1000 m, and 200-500 m is the most. The number of this group account 49.8% to the total. The erosion area in Heilongjiang province mainly belongs to water erosion(99.73%)(2) The severest gully erosion area in Heilongjiang province is gentle hilly and plain. Erosion gully in this area is concentrated on three obvious zones. The nuclear region of the first area is Great Khingan Mountain and its northern area with water erosion, and Songnen alluvial plain area. The nuclear region of the second belt is Lesser Khingan Mountains and its eastern area of piedmont alluvial and diluvial mesa. The nuclear region of the third area is ZhangGuangCai Mountain, runoff erosion area of Wanda Mountain with low hill and wide valley ridge, LaoYe Mountain, Taiping Mountain, and Qitaihe city with lava plainand low hill area.(3) Rainfall characteristics have significant influences on parameters of erosion gully. Dissected gegree and gully density was affected by average annual precipitation of flood season. Erosion gully number increased with the increase of average annual maximum 1 h precipitation, but it increased with the increase of average annual maximum 6 h, 24 h precipitation and then decreased. Average channel slope decreased with the increase of average annual maximum 6 h precipitation. But dissected degree and gully density increased with average annual maximum 6 h precipitation. Average erosion gully slope, dissected degree, gully density have quadratic polynomial function with average annual maximum 1 h precipitation. Gully number, dissected degree and gully density all increased with average annual maximum 3 day precipitation and then decreased.(4) The number of erosion gully has significantly differences under different land use. The erosion gully in farmland account 72.4% to the total erosion gully. Average channel slope of erosion in the grass land and forest land is higher than other land use. But the dissected degree and gully density in farmland is the highest. The shortest of unit channel length in farmland means most of farmland erosion gully is in puberty.(5) Taking gully density as the indicator, measurement urgency of erosion gully can be divided into four levels: severe urgency, urgency, light urgency and no urgency. And taking city and county as management unit, the study classified the urgency level of the erosion gully for the whole province.