Cross-section characteristics and hydraulic geometry of different erosion gullies on slopes

Gully erosion is one important cause of soil and water loss on slopes, and research on gully morphology is very necessary for understanding principles governing gully erosion and estimating sediment transport. The cross-section characteristics and hydraulic geometry of different erosion gullies on bare sloping land with loamy soil were studied through the collation and analysis of approximate 35 field data sets in China and abroad, and the criteria used to distinguish the erosion gullies were also given. Results showed that the width to depth ratio(ζ) gradually decreased with the development of erosion gullies, and the suitable range of ζ for rills, ephemeral gullies, gullies and streams were 5-17, 2-5, 0.4-1.8 and 0.1-0.6, respectively. The types of loamy soil also affected the ζ value for the same erosion form, and ζ increased as soil particle size increased. Different erosion gullies had different hydraulic geometry indices, and the exponents β₁, β₂ and β₃ were 0.3, 0.4 and 0.3 for rills, respectively; and correspondingly 0.4, 0.4 and 0.2 for ephemeral gullies and gullies; and 0.5, 0.4 and 0.1 for stream. Preliminary validation of the criteria indicated that they could be used to distinguish the different erosion gullies.