The gobi sand stream and its control over the top surface of the Mogao Grottoes, China

The paper discusses measures to protect the Mogao Grottoes, northwest China, from the effects of a gobi sand stream. Wind tunnel experiments show that gravel coverage is important for the aerodynamic roughness length when the wind velocity is lower than 10 m/s but decreases with increased wind velocity. When the wind velocity exceeds 10 m/s, the height of the gravel plays the more important role. The gravel both protects the ground surface and assists in arresting shifting sands. 40–60% of gravel coverage can keep the gobi beds in a relatively stable state despite the multi-directional winds. Wind tunnel experiments also show an upwind supply, or no supply of sediment are significant factors in the arrest and transport of sand. A comprehensive protection system, including upright sand-block fences, half-buried straw checkerboard barriers, irrigated sand-fixing plants, gravel mulch, and feather-like diversion works is discussed.